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Sensory analysis of food products

INTRODUCTION

sensory quality tasting

Sensory analysis is the science used to evaluate the quality of food products through tasting. The emergence and development of sensory analysis. Prospects for the development of sensory analysis. Psychophysiological foundations of the sensory method for researching food products

The concept of sensory physiology and sensory analysis. Sensory perception of food products is a complex psychophysiological process. The human analyzer system and its sections: peripheral, conductive and central. Functions of the nervous system and the mechanism of perception of sensations. Psychophysiology of sensations. Topography of the main spheres of sensation in the human brain. Factors influencing the impressionability of the senses: impulse strength, adaptation and physiological fatigue, etc. Basic concepts of sensory physiology: sense organs; modality, quality, specific sensory stimuli; amount of sensory impression and threshold stimulus; perception, display of an external phenomenon in perception.

The concept of taste and taste sensations. Morphology of taste organs and basic taste sensations. Information about the anatomy and physiology of the taste organs. Mechanism of taste perception. Taste method in assessing the quality of food products. Theories of taste perception and classification of tastes: sweet, salty, bitter, sour. Quantitative and qualitative human discrimination of taste stimuli. Testing a person's ability to identify the main types of tastes. Taste color blindness. Determining the threshold of taste difference and establishing the threshold of taste sensitivity. The concept of “deliciousness” of a product as a complex set of sensations. Reasons for decreased taste sensations (tasting conditions). Fatigue of the taste buds (fatigue of the taste organ).

1 NOMENCLATURE OF ORGANOLEPTIC INDICATORS OF PRODUCTS QUALITY

Organoleptic analysis of food and taste products is carried out through tastings, i.e. studies carried out using sense organs specialist taster without the use of measuring instruments.

Vision is one of the most important human tools that communicates with the outside world. In addition, vision is also the most important tool for a taster. Thanks to vision, the taster can assess the integrity of the product, its shape, degree of baking, color, age of the wine and its degree of oxidation, etc. Vision provides a huge amount of information for assessing the quality of a product. With the help of vision they determine:

1. appearance-- the overall visual sensation produced by the product;

2. form-- geometric properties (proportions) of the product;

3. color-- the impression caused by a light pulse determined by the dominant light wavelength and intensity;

4. shine-- the ability of the product to reflect most of the rays falling on the surface, depending on its smoothness;

5. transparency-- a property of liquid products that depends on the degree of light transmission through a layer of liquid of a certain thickness.

The sense of touch provides the taster with a wealth of information about the quality characteristics of the food product being evaluated. Without touch, it is impossible to fully assess the quality of a food product, since the tasting result will not be informative enough. Touch is the ability to perceive the action of environmental factors using receptors on the skin surface and oral mucosa. Product quality indicators assessed using deep touch (pressure):

1. consistency-- texture characteristic, reflecting the totality of the rheological properties of food products;

2. density-- property of product resistance that occurs when pressed;

3. elasticity-- the ability of the product to return to its original shape after cessation of pressure not exceeding a critical value (elasticity limit);

4. elasticity-- texture characteristic determined by the speed and degree of restoration of the original dimensions of the product after the cessation of the deforming effect;

5. stickiness-- the ability of texture, due to the force required to overcome the force of attraction between the surface of the product and the tongue, palate, teeth or hands;

6. plastic-- the property of the texture not to be destroyed during the process and after the cessation of the deforming effect;

7. fragility-- the property of texture to collapse under small sudden deformations.

The sense of smell is the most complex mechanism in the human body, which still holds many secrets and allows for a connection between smell, the brain and a person’s emotional sensations. The olfactory abilities of the taster allow him to comprehensively evaluate not only the smell or aroma of the product being evaluated, but also the delicacy (flavor) and quality of the product as a whole. Product indicators determined smell:

1. smell- a sensation that occurs when the olfactory receptors are excited, determined qualitatively and quantitatively;

2. aroma-- a pleasant harmonious smell characteristic of a given food product (ordinary wine, tea, drinks, fruits, spices, etc.);

3. "bouquet"- a pleasant developing aroma, formed under the influence of complex processes occurring during ripening, fermentation and fermentation (for example, the “bouquet” of aged wine).

When studying taste sensitivity, it is paramount to consider the structure of the taste organs and their connection with the central nervous system. The entire inner surface of the oral cavity, soft palate, and pharynx are covered with taste buds to varying degrees of localization. The largest number of them is on the tongue. Using the sensory organs in the oral cavity, the following parameters of product quality are determined:

1. juiciness- the impression of touch produced by the juices of the product during chewing (for example, the product is juicy, slightly juicy, dryish, dry);

2. uniformity- the impression of touch produced by the size of the product particles (uniformity of chocolate mass, candy fillings);

3. consistency- sense of touch, perceiving thickness,

4. stickiness product, pressure force; it is felt when the product is distributed on the tongue (the consistency is liquid, syrupy, thick, dense);

5. fibrousness-- the impression caused by fibers that provide resistance when chewing a product, which can be felt qualitatively and quantitatively (for example, meat with fine fibers);

6. crumbliness- the property of a solid product to crumble when biting and chewing, due to the low degree of adhesion between particles;

7. tenderness-- a conditional term, assessed as the resistance that a product has when chewing (for example, a soft apple, a crisp cucumber, tender meat);

8. astringency- a sensation of touch caused by the fact that the inner surface of the oral cavity tightens and at the same time dry mouth appears;

9. taste- a sensation that occurs when receptors are excited and is determined both qualitatively (sweet, salty, sour, bitter) and quantitatively (taste intensity);

10. flavor (flavor), or deliciousness, - a complex sensation of taste, smell and touch during the distribution of the product in the oral cavity - is determined qualitatively and quantitatively.

Texture - the term refers to the macrostructure of a food product, which is characterized by a complex of visual, auditory and tactile sensations that occur when the product is chewed. The texture can be hard, elastic, fibrous, porous, layered, soft, hard, tender, brittle, sticky, sticky, etc.

2. SCORING METHOD

2.1 Scoring method: advantages and disadvantages

Scoring is a method for assessing food products according to several quality indicators, in which their ratings, expressed in points, are summed up

A point scale is an ordered set of numbers and qualitative characteristics that are brought into correspondence with the objects being assessed according to a defined characteristic. It serves for quantitative assessment, which expresses the qualitative level of the attribute; * characterized by scoring - the number of quality levels included in the scale

Types of point scales

· nominal- numbers or symbols serve as symbols for identifying objects or their properties;

· ordinal - numbers indicate the sequence of objects or properties according to their degree of importance, while taking into account a certain connection between them;

· interval- derived from ordinal, indicate the size of the differences between objects or properties; in these scales, the distances between the symbols are equal and are set arbitrarily;

rational- just like interval ones, they reflect the ratio of the sizes of an object in the presence of a zero reference point[2 p.32].

Composing scales to measure subjective feelings is a difficult task. To do this, first of all, the following two issues must be resolved: choosing the volume (number of points) of the scale and identifying the relationship between the intensity of individual quality attributes and the digital values ​​of the scale. When choosing the volume of the point scale, they are guided by the required degree of accuracy, reliability of the results and the number of quality levels distinguishable by tasters. So, if tasters can only distinguish between five quality categories, a scale with 20 divisions is not needed.

Large fluctuations in the importance of one or another indicator of product quality are explained not only by the opinion of the authors of the systems, but also by the variety of properties of food products and the specific requirements for them.

Organoleptic characteristics of products are immeasurable, the values ​​of which cannot be expressed in physical dimensional scales. Characteristics of taste, smell, consistency and other sensory attributes are given in qualitative descriptions.

To convert quality into quantity, during expert assessment, dimensionless scales are used: usually in points, less often in fractions of a unit or percentage. The point scale is an ordered set of numbers and qualitative characteristics that are aligned with the objects being assessed according to the attribute being determined. The point scale serves for quantitative assessment, which expresses the qualitative level of the attribute. The scale is characterized by a range, or score, which refers to the number of quality levels included in the scale. The number of evaluation points does not always coincide with the number of points, since points can be divided into fractions (1.1; 1.5; 1.7 points, etc.) or not all points can be used in the assessment (5, 10, 15 , 20-50 points, etc.).

For example, a scale with the highest score of 5 points with a gradation of 0.5 points has the same range as a scale with a highest score of 10 points and a gradation of 1 point, and similarly a scale with a maximum score of 100 points and a gradation of 10 points. If these scoring scales do not use 0, then they all have the same range with 10 quality levels.

When developing point scales, the gradation of the scale is determined depending on the task at hand, the quality of the experts, the required accuracy of the results and the possibility of verbal description of the characteristics of quality levels. For expert assessment of product quality, it is recommended to use scales with an odd number of quality levels; more often, point scales are used that have 3, 5, 7, 9 gradations of quality, which may or may not coincide with the number of points. An experienced taster remembers and distinguishes only 6 - 10 levels of quality for each indicator.

A common disadvantage of scales containing a large number of points or a large number of quality levels is the presence of “dead zones” with unsatisfactory ratings, which, as a rule, are not used in the work of expert tasters.

There are known scales ranging from 3 to 120 points. The simplest is a 3-point scale, which evaluates changes in quality. An example of a 3-point scale is given in Table 1.

Table 1 - 3-point scale of various products during storage.

However, the 3-point scale does not allow for differentiated evaluation of the product, since it characterizes it according to a small number of quality levels. The most widespread in the practice of organoleptic assessment are 5-point scales. An example of a 5-point scale is given in Table 2.

Table 2 - 5-point scale of various products during storage.

The use of a 5-point scale allows a taster with average sensory sensitivity and experience to obtain fairly accurate results.

When using a five-point system in conditions of comparative assessment of several samples, tasters may need to make a more differentiated assessment of them, for example, half a point, or express their attitude towards the product in addition to the assessment of points with plus or minus signs. The five-point rating system can be considered the main or reference system, since it underlies the seven- and nine-point scales.

Close to the 5-point scale and easily convertible into it is the 6-point scale, in which five of the six levels are intended to assess an acceptable product, and one is intended to characterize a product that is not suitable for human consumption. This level is expressed as zero.

Nine-point scales are also widely used in determining the organoleptic characteristics of food products. The general scheme of the nine-point rating scale takes into account typical ones.

Such a scheme can only serve as a basis for assessing the specific quality of various products, since there are no characteristic descriptions of the objects of study, which complicates the work of tasters.

Ten- and eleven-point scales are not used very often, because they have a number of disadvantages. So, V on a ten-point scale for assessing the quality of food products, developed in Norway, the analytical assessment in points is combined with an assessment of preference. Working with this scale is complicated by the fact that it combines two important indicators such as “taste” and “smell”.

For the organoleptic assessment of various food products, both twenty- and thirty-point scales have been developed.

In most cases, when using them, the total amount determined by organoleptic analysis is calculated as the sum of indicators assessed separately (taste, smell, consistency, appearance). Each indicator in these scales is analyzed according to 3-6 quality levels and assessed with no more than ten points, which ultimately makes it possible to reduce twenty- and thirty-point scales to simpler ones.

There are scales with a number of points from 30 to 100. The disadvantage of 100-point scales used in the organoleptic evaluation of food products is the lack of description of each point on the scale. 100-point scales are compiled differently depending on the nature of the product and the relative importance of each of the main organoleptic indicators involved in quality assessment.

Each indicator is assigned a certain maximum number of points so that the total is 100. Then the amount of discounts is established for each partial (for individual indicators) point estimate for the commercial varieties provided for by the standard. An example of a 100-point scale is given in Table 3.

Table 3 - 100-point scale of various products during storage.

Discounts for each type of product are not set the same, but taking into account their specifics.

A significant advantage of multi-point systems compared to low-point systems is the wide range of the scale, which is several times greater than the working ranges of other point systems [2 p.48].

2.2 X characteristics of the weight coefficient

Weight factor- quantitative characteristics of the significance of the indicator among other indicators when calculating a complex quality indicator. The weighting factor can be determined based on expert opinion. In its simplest form, a complex quality indicator is the sum of the product of estimates of individual quality indicators and their weight.

Expert and analytical methods are used to determine these coefficients. Experts can use ranking, paired and sequential comparison methods. In this case, it is necessary to highlight the main indicators that most reflect the ability of the product to fulfill its functional purpose. For example, for food products such indicators as taste, smell and consistency are of greatest importance, therefore it is recommended to allocate 40 to 60% to taste and aroma indicators, and 20-25% to consistency. In accordance with existing methods of qualimetric assessment of the quality of goods, the sum of weight coefficients can be any constant number. But in commodity practice, the sum of weight coefficients equal to 20 or 1 is most often used. In the first case, the 5-point scale is transformed into a 100-point scale and the complex quality indicator is perceived as a percentage of optimal quality. Product quality categories are determined based on the gradation of points proposed by experts.

The weight parameters of quality indicators play an important role in the assessment and have a significant impact on the final result of the calculation. Among the main methods for determining weight parameters, the following should be noted:

· expert;

· limit and nominal values;

· equivalent ratios;

· cost regression dependencies (cost).

Each of them has its own characteristics, advantages and disadvantages. For market conditions (when an assessment is required based on multiple indicators for a certain period, a specific segment, etc.), the most preferable method for solving problems of quality assessment is the expert method.

When expertly determining the parameters of the weight of quality indicators, as well as many other tasks in QM, the methods of preference (ranking), evaluation and comparison are most widely used. The use of expert methods to determine the parameters (coefficients) of the weight of indicators requires compliance with the rules and the implementation of the same expert procedures as when using expert methods.

According to the preference (rank) method, each expert, providing the entire selected range of quality indicators of the products being assessed, numbers (ranks) the weight of indicators in the order of their preference and importance. The least important indicator is assigned the number 1, the next most important - 2, etc., i.e. the most important indicator receives the last number, the most insignificant - the first.

The evaluation method (assigning points) involves an expert ranking the importance of each quality indicator by scoring on a certain point scale. The expert can assign the maximum number of points to the most important indicator.

Determination of weight parameters using the expert comparison method is carried out by paired and sequential comparisons. In pairwise comparison, the expert compares quality indicators according to their importance in pairs, choosing the most significant one in each pair.

In some cases, the weight coefficients of a number of individual and group indicators should be determined on the basis of the sociological method, compiling information based on assessments of real and potential consumers. This is especially useful when assessing the level of quality by manufacturers when making decisions during the period of establishing the required level of quality, as well as at all subsequent stages and stages of the product life cycle; The needs and capabilities of the target market for a specific period of time should also be taken into account.

Method of limit and nominal values. This method is used in cases where experimentally verified maximum permissible values ​​for quality indicators of a given type of product are known, which determine the requirements for a suitable product or whether it belongs to a given quality category. In these cases, the weighting factors for various types of weighted averages

Method of equivalent relations. This method is used in cases where it is possible to justify what relative change in the quantity of products is equivalent, from the point of view of the overall effect of using the product for its intended purpose, to the considered relative change in a given quality indicator or by what percentage it is possible, for example, to reduce the number of units of production in order to ensure those the same needs with an increase in this quality indicator by 1%[3p.57].

3 . CLASSIFICATION OF TASTERS AND TASTERS ACCORDING TO THE INTERNATIONAL STANDARD FOR SENSORY EVALUATION

3 .1 Expert methods of tasting analysis

Tasting analysis allows you to solve various problems throughout the entire life cycle of products: from creation to implementation and monitoring the quality of the product during production and storage, identifying drift and falsification. Knowledge and correct application of tasting analysis methods is the key to the objectivity of its results. The fundamental methods are those developed by the International Organization for Standardization (ISO). Let's consider the classification and scope of problem solving of tasting analysis methods.

All methods of tasting analysis according to ISO 6658 can be divided into expert and consumer assessment methods. Expert, or analytical, methods of tasting analysis, in turn, are divided into distinctive and descriptive

Distinctive methods of tasting analysis include qualitative ( paired comparison method, triangular method,“duo-trio”, multiple standards method, “A” - “not A”, ranking method) And quantitative(dilution index method, scoring method)

Discriminating qualitative methods are based on comparing two similar samples A and B with subtle differences, for example:

1) “duo-trio” (“Duo-Trio” Test according to ISO 10399). An organoleptic method for evaluating two pairs of coded samples by comparing them with a designated standard sample. It is used for analytical purposes to establish differences in individual quality indicators.

2) paired comparison (Paired Companion Test according to ISO 5495). This method is based on ranking two coded samples. The taster needs to compare two samples with subtle differences. When using this method, the taster evaluates 6-8 coded pairs of samples. In pairs, two samples that differ little from each other are assembled. In all pairs, the same tests are offered, but in a random order. The taster determines in each pair a sample with a more pronounced degree of expression of the trait.

3) “two out of five” (“Two From Five” Test according to ISO 67240). An organoleptic method for evaluating two samples of a product, represented by five coded samples, three of which are identical to one sample and two to another, by dividing the samples into two appropriate groups. Used to determine subtle differences;

4) triangular (Triangle Test according to ISO 4120). This method is based on selecting a different sample from three coded samples, two of which are identical. During the implementation of the method, the taster is asked to compare three samples, two of which are identical;

5) “A” - “not A” (“A” - “not A” according to ISO 8588). This method of organoleptic evaluation consists in the identification by the taster of the tested samples (“A” and “not A”) in the proposed series of coded samples, i.e. the taster is invited, after preliminary acquaintance with the standard (“A”) and different (“non-A”) product samples, to identify them in a series of coded samples;

6) rank (Rank Order Test according to ISO 8587). This is an organoleptic method of evaluating coded samples by placing them in order of change in intensity or degree of expression of a given product characteristic. When using this method, the taster is asked to arrange randomly submitted coded samples in order of increasing or decreasing intensity of the assessed characteristic;

7) method of multiple standards. An organoleptic method of selecting from a given series a sample that differs significantly from standard samples, representing the product in several forms (from two to five).

Discriminative quantitative methods quantify the intensity of a particular property, for example:

1) Dilution Index Method. Designed to determine the intensity of odor, taste, and color of a product based on the maximum dilution value. Mainly used for liquid products. Allows you to observe a change in a particular stimulus depending on any factor (production conditions, storage) and express it in the form of absolute numbers

2) scoring method (Scoring Test). Allows you to quantify the quality attributes of products. The method is based on the use of graphic or verbal scales. The taster is offered two samples of the product, for which the characteristic being assessed has a maximum and minimum value, and one sample for which the intensity of the characteristic is unknown. When comparing the third sample with the first two, the relative value of the characteristic is assessed and marked on the scale with a perpendicular stroke, taking into account the distance at both ends. It is used when creating new products to determine the optimal value of product characteristics.

Descriptive (descriptor) methods of tasting analysis are methods of qualitative assessment of each of the separately considered properties of a food product using their qualitative characteristics (descriptors), standardized or non-standardized. The task of descriptive methods is to use precise terminology that does not allow for discrepancies.

1. Point Method. Used for differentiated analysis carried out by highly qualified tasters. This is an organoleptic method for evaluating a food product according to several quality indicators, in which their ratings, expressed in points, are summed up.

The significance coefficients of each feature are used. In foreign practice, the method is rarely used, but in Russia it is one of the main methods of tasting analysis. The assessment results are expressed in the form of points on a conventional scale with an increasing sequence of numbers, each of which corresponds to a certain intensity of a particular quality indicator.

2. Profile, or descriptor-profile, method (Flavour Profile Method according to ISO 6564). An organoleptic method for assessing a set of characteristics (aroma, taste, consistency) using pre-selected descriptive characteristics-descriptors. It implies a verbal description and quantitative expression of organoleptic characteristics, assessed in points and graphically, arranged according to a diagram. The characteristic nuances of the signs, their intensity, the order in which the shades appear, and the aftereffect are called the product profile.

The profile method is based on the fact that individual gustatory, olfactory and other stimuli, when combined, give a qualitatively new definition of the deliciousness of the product.

Identification of the most characteristic taste elements for a given product allows us to establish the product’s deliciousness profile, as well as study the influence of various factors (technological modes, storage conditions, raw materials). First, the odor profile is determined, then the taste and consistency.

Then the intensity level of each feature (descriptor) is determined. This method can be used to assess the quality of products with complex characteristics. This method, also called the descriptor-profile method (DP method) in foreign practice, is the most promising and can be used in the development of new products with specified consumer properties.

3.2 Consumer tasting methods

Consumer assessment methods are used to study consumer reactions to a food product (for example, a new product) or when making changes to technology, transportation or storage conditions. These methods are successfully used by marketers to assess the competitiveness of a brand and assess the perception of a new product.

Consumer assessment methods include: preference method, preference ranking method, method for determining product acceptability, method for determining product desirability, method for determining “relevance”. Consumer assessment methods are based on the hedonic principle of “like it - don’t like it”. The consumer tasting commission, depending on the required accuracy of the results, should consist of 30-100 untrained respondents belonging to the target audience for product consumption, whose gender and age depend on the nature of the tasting and taste preferences.

1. Preference method. It is used to determine the preference of one product over another at the stage of improving its characteristics or to determine the competitiveness of a brand. It is based on intuitive responses from consumers and gives a complete and comprehensive impression of the preferences of the target audience.

2. Preference ranking method. It is used to determine the increase or decrease of preferences in the line of proposed samples. It can be used not only for a comprehensive organoleptic assessment of a product, but also for assessing the variable properties of a product.

3. Method for determining product acceptability. Allows you to assess the level of acceptability of the product. Consumers rate their impressions based on personal feelings using a hedonic scale. The hedonic scale (from the gr. hedone - pleasure) can be made in the form of both a verbal description and a graphic scale of drawings. The latter is used when the target audience is children.

4. Method for determining desirability. Allows you to assess the level of desirability of a product or variable attribute when consumers, based on personal feelings, evaluate their impression using a hedonic scale.

5. Method for determining “relevance”. It is used to assess the effect of external factors (meal time, cultural traditions, etc.) influencing the organoleptic perception of consumers.

CONCLUSION

Thus, we can say that the rapidly developing food market and, as a consequence, the increasing competitive environment, the abundance of chemically synthesized food additives, and the emergence of genetically modified products adversely affect the health of the Russian population. Food manufacturers today face a serious challenge - without losing the target customer and the profitability of production, to create popular products with high consumer properties. In order to survive in a global economic crisis, a manufacturer must have knowledge of marketing communications, foresight and intuition, information about competitive advantages and disadvantages, and deep knowledge of technological processes. There is increasing interest in the use of organoleptic analysis methods, which allow saving marketing budgets and producing not just new, but popular products, including functional ones, the sales of which will be guaranteed.

LITERATURE

1. Bazarnova Yu.G. Methods for studying raw materials and finished products: Educational method. allowance. SPb.: NRU ITMO; IKhiBT, 2013. 76 p.

2. Denisova A. L., Zaitsev E. V. Theory and practice of expert assessment of goods and services: Textbook. allowance. Tambov: Tamb publishing house. state tech. Univ., 2002. 72 p.

3. Nedbay, A. A. Fundamentals of qualimetry. 1.0 A. A. Nedbay, N. V. Merzlikina. - . (2 MB). - Krasnoyarsk: IPK SFU, 2008

4. Chugunova, O. V. The use of tasting analysis methods in modeling food product recipes with given consumer properties [O. V. Chugunova, N. V. Zavorokhina; Ministry of Education and Science of the Russian Federation, Ural. state econ. univ. - Ekaterinburg: Ural Publishing House. state econ. University, 2010. - 148 p. - Bibliography: p. 129-140 (132 titles).

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1

Currently, tasting methods for assessing the quality of food products have become widespread, because in terms of accuracy and objectivity, sensory assessment is to some extent close to the results obtained by other methods of analysis, and in many cases the results obtained from organoleptic tests cannot be obtained in any other way. The fundamental methods are those developed by the international organization for quality (International Organization for Standardization, ISO). The work presents the classification and areas of solving problems of tasting analysis methods.

descriptor-profile method

sensory analysis

organoleptic analysis

food quality assessment.

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SCIENTIFIC REVIEW: ANALYSIS OF TOUCH AND ITS SIGNIFICANCE IN THE EVALUATION OF QUALITY AND FOOD SAFETY

Chugunova O.V. 1

1 Ural State University of Economics

Abstract:

Currently, methods for assessing food tasting food quality have become widespread since accuracy and objectivity in the sensory evaluation somewhat closer to results obtained by other analysis methods, and in many cases the results obtained by organoleptic tests can not be obtained in another way. The fundamental methods are developed by the International Organization for Quality (International Organization for Standardization, ISO). The paper presents classification and scope of solving the tasting analysis.

Keywords:

descriptive and profile method

sensory analysis

sensory analysis

evaluation of the quality of food food.

According to GOST R 5492-2005 Sensory analysis: analysis using sensory organs (highly specific receptor organs), providing the body with information about the environment through vision, hearing, smell, taste, touch, vestibular reception and interoreception.

Organoleptic analysis: sensory analysis of products, flavors and aromatic substances using smell, taste, vision, touch and hearing. The term is not synonymous with sensory analysis; its meaning is limited by the object of study and the number of sense organs.

The term "organoleptic" comes from the Greek words "organon" (tool, instrument, organ) and "lepticos" (prone to take or receive) and means "detected by the senses." The term "sensory" also means "feeling" and comes from the Latin word "sensus" (feeling, feeling). In foreign literature, the term “sensory” is predominantly common. One interpretation of the English word “sense” means “feeling”.

To assess the organoleptic properties of food products, tasting methods based on the analysis of sensations from the human senses are widely used. The organoleptic properties of a product, much more than its chemical composition and nutritional value, influence consumer choice and ultimately shape their demand.

Tasting or organoleptic (sensory) assessment, carried out using the human senses, is the most ancient and widespread way of determining the quality of food products. Existing methods of laboratory analysis are more complex and labor-intensive compared to organoleptic assessment methods, and only allow the characterization of specific quality attributes. Tasting analysis quickly and with the correct analysis objectively gives a general impression of the quality of the products.

Tasting analysis allows you to solve various problems throughout the entire life cycle of products: from product creation to its implementation and monitoring the quality of the product during production and storage, identifying drift and falsification. Knowledge and correct application of tasting analysis methods is the key to the objectivity of its results.

Scientifically organized tasting analysis is superior in sensitivity to many laboratory testing techniques, especially in relation to such indicators as taste, smell and consistency. Errors in sensory analysis most often occur with an unprofessional approach to this assessment method. The existing opinion about the subjectivity and non-reproducibility of organoleptic assessments is caused mainly by the fact that the individual characteristics of tasters are not taken into account, they are not specially trained and trained in sensory analysis techniques, the basic rules and conditions of a scientifically based organoleptic method are not met, in particular, sensory testing is not carried out abilities of tasters, the requirements for the room in which sensory analysis is carried out are not met, and due attention is not paid to the choice of assessment method. The last circumstance is one of the most important for obtaining reliable and comparable results.

When selecting a tasting evaluation method, preference is given to point systems with the obligatory differentiation of quality characteristics by importance (significance) when forming a general impression of the quality of the product under study.

The fundamental methods are those developed by the international organization for quality (International Organization for Standardization, ISO). Below are the classification and areas of problem solving of tasting analysis methods.

Application of expert methods of tasting analysis in assessing the quality and safety of food products

All tasting analysis methods, according to ISO 6658, can be divided into expert (analytical) and consumer assessment methods. Expert methods of tasting analysis, in turn, are divided into discriminative and descriptive methods.

Analytical methods of organoleptic analysis are based on a quantitative assessment of quality indicators and make it possible to establish a correlation between individual characteristics.

Discriminating analytical methods.

Distinctive methods of tasting analysis include: qualitative (paired comparison method, triangular method, duo-trio, multiple standards method, A-not-A, rank method) and quantitative (dilution index method, scoring method).

Discriminating qualitative methods are based on comparing two similar samples A and B with weakly expressed differences and answer the question: is there a difference between the evaluated samples in one of the quality indicators (taste, smell, consistency, etc.), but do not answer the question : what is the difference between the samples. These methods include:

Duo-trio (“Duo-trio” test according to ISO 10399). An organoleptic method for evaluating two pairs of coded samples by comparing them with a designated standard sample. It is used for analytical purposes to establish differences in individual quality indicators. To implement the method, the taster first evaluates a standard sample, and then two samples, one of which is identical to the standard one. Two samples are completed in the form of 6-7 paired samples, which are coded. The taster is asked to identify in each sample a sample identical to the standard one.

Paired companion test according to ISO 5495. This method is based on ranking 2 coded samples. The paired comparison method is based on comparing 2 samples with subtle differences. When using this method, the taster evaluates 6-8 coded pairs of samples. In pairs, 2 samples that differ little from each other are completed. In all pairs, the same tests are offered, but in a random order. The taster determines in each pair a sample with a more pronounced degree of expression of the trait. The answer may be to recognize the samples as the same or different. Only one product property can be assessed at a time (for example, aroma intensity, color intensity, flavor intensity). The paired comparison method is convenient to use to determine the influence of any factor on the quality of a product: changing the recipe, production technology or storage.

Two from five test. An organoleptic method for evaluating two samples of a product, represented by five coded samples, three of which are identical to one sample and two to another, by dividing the samples into two corresponding groups. Used to determine subtle differences.

Triangular (triangle test according to ISO 4120). The triangular method is based on selecting a different sample from three coded samples, two of which are identical. During the implementation of the method, the taster is asked to compare three samples, two of which are identical.

A-not-A (“A”-not-“A” according to ISO 8588). This method of organoleptic evaluation consists in the identification by the taster of the tested samples (“A” and “not A”) in the proposed series of coded samples, i.e. The taster is invited, after preliminary acquaintance with the standard (A) and different (non-A) product samples, to identify them in a series of coded samples.

Rank method (rankordertest according to ISO 8587). This is an organoleptic method of evaluating coded samples by placing them in order of change in intensity or degree of expression of a given product characteristic.

When using this method, the taster is asked to arrange randomly submitted coded samples in order of increasing or decreasing intensity of the assessed characteristic.

Multiple Standards Method. An organoleptic method of selecting from a given series a sample that differs significantly from standard samples representing the product in several forms (from two to five).

Discriminative quantitative methods quantify the intensity of a particular property or the quality level of a product. These methods include:

Dilution index method. Designed to determine the intensity of odor, taste, and color of a product based on the maximum dilution value. Mainly used for liquid products. Allows you to observe changes in a particular stimulus depending on any factor (production conditions, storage and express it in the form of absolute numbers.

Scoring method (SCORING test). Allows you to quantify the quality attributes of products. The method is based on the use of graphic or verbal scales.

The taster is offered two samples of the product for which the characteristic being assessed has a maximum and minimum value and one sample for which the intensity of the characteristic is unknown. When comparing the third sample with the first two, the relative value of the characteristic is assessed and marked on the scale with a perpendicular stroke, taking into account the distance at both ends.

It is used when creating new products to determine the optimal value of product characteristics.

The scoring method makes it possible to quantify the qualitative characteristics of a product and opens up great opportunities for studying the correlation between the organoleptic properties of a product and objective parameters measured by instrumental methods.

Descriptive analytical methods are methods for qualitative assessment of each of the properties of food products under consideration using a list of their qualitative characteristics (descriptors), standardized and non-standardized. The task of descriptive methods is to use precise terminology that does not allow for discrepancies. These methods include:

Directly descriptive method - the results of this method are included in almost every regulatory and technical document for food products and regulate their standard organoleptic qualities. For example, clause 4.1.7 of GOST R 53396-2009 “White sugar. Technical specifications" states: In terms of organoleptic indicators, the product must meet the requirements of Table 1.

The advantages of this method: simplicity, does not require large time, material and energy costs.

The organoleptic quality indicators given in each GOST can be considered as a system of guidelines that allows you to quickly determine the required quality indicators of products when receiving goods, classify the product into a particular variety or category, and also helps producers when purchasing agricultural raw materials in the consumer cooperation system.

Table 1

Organoleptic quality indicators of white sugar

Name indicator	Characteristics of white sugar
	crystalline	powdered sugar	lump
	White, pure		White, clean, free of stains and foreign matter
Appearance	Homogeneous free-flowing mass of crystals	Homogeneous free-flowing mass of crushed crystals	In the form of pieces of certain sizes
Taste and smell	Sweet, without foreign taste and odor, both in dry sugar and in its aqueous solution
solution	The sugar solution must be transparent, without insoluble sediment, mechanical and other impurities

Disadvantages: lack of clear terminology to describe sensory sensations. To solve this negative property of the descriptive method, the profile or point method is used.

The Point method is a method for assessing the quality of food products based on several quality indicators, in which their ratings, expressed in points, are summed up. Used for differentiated analysis carried out by highly qualified tasters.

The assessment results are expressed in the form of points on a conventional scale with an increasing sequence of numbers, each of which corresponds to a certain intensity of a particular quality indicator.

There are 4 types of scales:

Nominal - numbers or symbols serve as symbols for identifying objects or properties of these objects;

Ordinal - numbers indicate the sequence of objects or properties according to the degree of their importance, while taking into account a certain connection between them;

Interval - derived from ordinal, denote the size of the differences between objects or properties; in these scales, the distances between the symbols are equal and are set arbitrarily;

Rational - just like interval ones, they reflect the ratio of the sizes of an object in the presence of a zero reference point.

The most commonly used are 10, 20 and 100 interval scoring systems. If a product is assessed according to one quality indicator, then a 5-point scale is used.

When summing up assessments, the weight coefficient of each of the quality indicators is often used. In foreign practice, the method is rarely used; in Russia it is one of the main methods of tasting analysis. The method allows you to set the levels of partial (for individual indicators) and general (for a set of indicators) quality.

The organoleptic assessment of the product must be carried out by a specially trained team of tasters, consisting of 5-7 people with tested sensitivity.

Currently, each food product is rated on its own point scale. For example, cheeses are rated on a 100-point system, soft drinks on a 25-point system, sausages on a 9-point system, etc. There are also special catalogs for describing the taste, smell, consistency, and pattern of cheeses. For example, 77 terms are used for Dutch cheese, and 64 for butter. A dictionary of 156 terms to describe the taste and smell of beer is grouped into a “wheel of taste”, which makes it easier to remember these terms.

When using a scientifically based scoring system and observing other basic requirements (for example, the order in which samples are submitted), the method allows one to obtain fairly objective, reliable, and highly reproducible results.

Profile (Flavour profile methods according to ISO 6564). An organoleptic method for assessing a set of characteristics-properties: aroma, taste, consistency using pre-selected descriptive characteristics. It implies a verbal description and quantitative expression of organoleptic characteristics, assessed in points and graphically, arranged according to a diagram. The characteristic nuances of the signs, their intensity, the order in which the shades appear, and the aftereffect are called the product profile.

The profile method is based on the fact that individual gustatory, olfactory and other stimuli, when combined, give a qualitatively new definition of the deliciousness of the product. Identification of the most characteristic taste elements for a given product allows us to establish the product’s deliciousness profile, as well as study the influence of various factors (technological modes, storage conditions, raw materials). First, the odor profile is determined, then the taste and consistency. Then the intensity level of each feature (descriptor) is determined. This method can be used to assess the quality of products with complex characteristics.

A verbal description or quantitative expression of organoleptic characteristics, assessed in points or graphically and arranged according to a scheme: characteristic shades of characteristics, their intensity, the order of manifestation of shades, consequences - is called a product profile.

When using the profile method, various scales are used:

Ordinal, in which the assessment is given in numbers or as a point on a segment 10 cm long;

Relative scales, in which the assessment is given in relation to the selected standard of intensity of characteristics (descriptors);

Graphic scales in which the assessment is given: in the form of a graph or step chart, where descriptors or their numbers are plotted along the abscissa axis, and the intensity of sensation is plotted along the ordinate axis; in the form of a pie chart, where the number of radii corresponds to the number of descriptors, and their intensity is marked by a point on the radius distant from the center; after connecting all the points, a profile is obtained in the form of a radar diagram.

The last described method, also called “profile” in foreign practice, in our opinion, is the most promising and can be used in the development of new products with specified consumer properties.

The role of consumer tasting methods in assessing the quality and safety of food products

One of the modern trends in the development of tasting analysis is consumer sensory assessment - the most important element of both marketing research and assessment of product quality. It allows you to determine consumer preferences and understand which sensory characteristics of the product are preferable for them, i.e. obtain information about the consumer's impression of the product.

Methods aimed at establishing the reactions of consumers (users of products) when evaluating certain samples are called consumer methods.

Consumer assessment methods are used to study the reaction of consumers to a food product, for example, a new product or when making changes in technology, transportation or storage conditions. These methods are successfully used by marketers to assess the competitiveness of a brand and assess the perception of a new product.

When conducting a consumer assessment, tasters evaluate a new product, but with modified recipe components or technological regimes, with a product prepared in a traditional way.

Consumer assessment methods refer to emotional-consumer (affective) methods that involve the involvement of a large number of tasters and include tests to determine how the consumer feels and reacts to the product and evaluate preferences, acceptability, and “like-dislike” attitudes. .

Consumer reactions may be indirectly related to the presence or absence of specific signs. Does the consumer like the product? How much does he like it? Which sample has a more delicate consistency? Do consumers prefer this product enough to always buy it over others like it? Is the product acceptable although the consumer prefers less spicy?

The tasters in such studies should be consumers of the products. A panel of consumer tasters should include a larger number of participants than a trained panel because conclusions drawn from test results in a given group must be extrapolated to the general population. Consumer panelists do not undergo special selection or training, except when demographic profiles of large populations are being determined. Consumer tastings are aimed at identifying the tasters' attitude towards the product as a motivating reason for consumer behavior in general.

Consumer assessment methods include: preference method, preference ranking method, product acceptability method, product desirability method, and “relevance” method. Consumer evaluation methods are based mainly on the hedonic principle of “like - dislike”.

The consumer tasting commission, depending on the required accuracy of the results, should consist of 30-100 untrained respondents belonging to the target audience for product consumption, whose gender and age depend on the nature of the tasting and taste preferences.

Preference method. It is used to determine the preference of one product over another at the stage of improving its characteristics or to determine the competitiveness of a brand. It is based on intuitive responses from consumers and gives a complete and comprehensive impression of the preferences of the target audience.

When developing preference methods, great care is taken to keep the questionnaires presented to tasters as simple as possible, since they are ordinary consumers. The best results are obtained when consumers are presented with simple hedonic scales that require them to make appropriate marks depending on their opinions about the samples being evaluated. There are different types of scales. The simplest of these are the verbal hedonic scale and the face hedonic scale.

Preference ranking method. It is used to determine the increase or decrease of preferences in the line of proposed samples. It can be used not only for a comprehensive organoleptic assessment of a product, but also for assessing the variable properties of a product.

Method for determining product acceptability. Allows you to evaluate the level of acceptability of a product or to find out why one product is more acceptable than another. In contrast to descriptive methods, acceptability methods involve consumers and never involve trained experts.

Eligibility methods can be used:

To maintain a product on the market if its share falls.

To improve or optimize the product.

When creating a new product.

Method for determining desirability. Allows you to assess the level of desirability of a product or variable attribute when consumers, based on personal feelings, evaluate their impression using a hedonic scale. Consumer desirability is an important criterion for assessing quality, but the consumer’s attitude towards a product depends on many factors, both subjective (habit, prejudice, etc.) and objective (economic, advertising).

Method for determining "relevance". It is used to assess the effect of external factors (meal time, cultural traditions, etc.) influencing the organoleptic perception of consumers.

The methods of tasting analysis discussed above are fundamental and are used depending on the goals and objectives.

Potential of the descriptor-profile method of tasting analysis

The need of the hour is the development and application of new methods of tasting analysis in the food industry, which allows not only to develop high-quality and attractive products for consumers, but also to be economically profitable for the enterprise. Today, in addition to commodity science, other branch sciences are also interested in the development of sensory methods. Technological food industries and marketing need express methods for analyzing the organoleptic properties of food ingredients and finished products and assessing their consumer properties.

Of great importance here is the use of a comprehensive, cost-effective, fairly easy to implement, providing a rich information base of the descriptor-profile method of tasting analysis (DMA).

Descriptor-profile method (DPM) is a method of quantitatively displaying the totality of the most significant organoleptic characteristics of a food product: aroma, taste, consistency in the form of graphic profilograms, using pre-selected descriptors.

A descriptor is an individual characteristic of a food product that most clearly reflects its specified properties, allowing one to distinguish competitive products from each other. The most significant descriptors of taste, aroma, texture, etc. form a panel of descriptors that reflects the sensory perception of the product as a whole.

Application of the descriptor-profile method in the field of quality assessment

The period of the most active domestic developments in the field of organoleptic analysis dates back to the 70-80s of the 20th century.

Under the leadership of G.L. Solntseva, a scale for assessing the quality of meat products was constructed and a methodology for selecting tasters for the meat processing industry was developed; Test programs for the training of fish processing industry tasters have been developed under the leadership of T.M. Safronova; A.I. Chebotarev developed a methodology for selecting tasters for the dairy industry; a commission was created under the Committee of Scientific and Technical Terminology at the USSR Academy of Sciences under the leadership of R.V. Golovny.

After the collapse of the Soviet Union and at the beginning of the Perestroika period, scientific activity in the direction of the methodology of organoleptic analysis was practically curtailed and only resumed in full at the end of the 90s.

Today, the leaders in the development of tasting methods for quality assessment are the All-Russian Research Institute of the Meat Industry, Moscow State University of Food Production, Russian Economic Academy named after G.V. Plekhanov, Scientific and Production Association of Food Concentrate Industry and Special Food Technology. Russian researchers Solntseva G.L., Golovnya R.V., Safronova T.M., Rodina T.G., Duborasova T.Yu. made a great contribution to the development of organoleptics. .

Today, in addition to commodity science, the main function of which is to study issues related to the quality of consumer goods, other branch sciences are also interested in the development of sensory methods. Technological food industries and marketing need express methods for analyzing the organoleptic properties of food ingredients and finished products and assessing their consumer properties.

One of the ways to increase the competitiveness of products is to introduce sensory analysis into quality control. The sensory control program is an integral part of the enterprise’s quality management system in accordance with international standards ISO 9000.

The primary purpose of a sensory analysis program as part of quality control is to measure the extent to which the sensory characteristics of a product meet quality standards.

The sensory analysis program is used to detect product nonconformities during the production process, and not just at the final stage in the finished product. The results of sensory analysis may be the basis for product rejection.

Of great importance is the use of a comprehensive, cost-effective, fairly easy to implement, providing a rich information base descriptor-profile method of tasting analysis.

Historically, in sensory analysis, the profile method was used to evaluate the quality of food products, where descriptive characteristics and a visual profile were combined into "qualitative judgments" of tasters about the acceptability of the product. Through the profile tasting method, expert tasters identified defects, judged their severity and, accordingly, made decisions about the acceptability or unacceptability of a given product. This approach has for many years limited the applicability of this universal method for assessing quality and organoleptic characteristics for products where quality standards have not yet been defined, for example, for innovative instant products, yoghurts, national products.

The profile method of tasting analysis is used mainly to assess the quality of food products of complex composition: for example, to assess the quality of sauces, coffee, chocolate. Thus, Russian scientists T.G. Rodina and O.A. Goncharenko compiled flavor profiles for smoking preparations and flavorings. Many tasters, accustomed to the point method, are hesitant to use the profile method, considering it complex and insufficiently objective.

Unlike Russia, this method is considered the most promising abroad and is widely used.

Application of the descriptor-profile method of tasting analysis in the development of new products

The development of a new product using the descriptor-profile method of tasting analysis allows us to form a visual model of the taste and aromatic characteristics of this product. This becomes possible by comparing the variations of the product being developed relative to each other and then selecting the recipe that received the maximum rating from tasters. The individual characteristics of a food product (descriptors) created during development make it possible to change the taste and aromatic characteristics of the product depending on their quantitative value.

In the 70s of the twentieth century, scientists, employees of the Tragon company (USA) Sidel J. and Stown H. patented a method of quantitative profile analysis, which they called Qualitative Data Analysis (QDA™) - qualitative data analysis and introduced the concept of “descriptor” ". A descriptor, according to Sidel H. and Stown J., is an individual characteristic unique to this product. Descriptor-profile visual studies can be classified as the most highly informative class of sensory tests.

These methods provide for the quantitative display of the most significant organoleptic characteristics of a food product, reflecting its individual qualities, in the form of graphic profilograms. This is possible through the use of a set of scales, each of which provides a numerical response for the perceived intensity of a particular sensory attribute. Each specific descriptor is an independent descriptive feature that relates only to a given product. . Created by Tragon co-founders Dr. Herbert Stone and Joel L. Sidel, QDA™ is used to compare the flavor characteristics of foods and their competitiveness.

The very first experience of American scientists was the use of the “Aromatic Profile Method”. A group of specially trained expert tasters made a conclusion about the composition of the complex of aromas of the food product, the intensity of each aroma, and the order of their appearance. The individual product aroma profiles that were created were discussed extensively, resulting in one profile that all tasters agreed on.

Quantitative descriptive analysis made it possible to introduce aspects of consumer behavioral methodology into expert sensory assessment of the organoleptic properties of a product and make this method popular not only among tasters, but also among foreign marketers.

The methodology for constructing the aromatic profile was supplemented by the theory of creating a descriptor model with a model for quantitative determination of the intensity of properties.

This allowed testers to combine tasting evaluation methods with statistical calculations, and the latter, in turn, allowed them to compare products with each other.

With the help of CSA, along with the results of hedonic studies within a certain range of products, its organoleptic advantages and disadvantages can be identified, including for comparison with competitors' products. During product development, as well as for quality assurance purposes, these methods can be used to assess compliance with specified goals. . Thus, scientists A. Kohan and M. Grimm (Germany) used the descriptor-profile method when assessing the quality of dessert chocolate. They identified fourteen descriptor signs: four signs for assessing appearance (shine on the top and bottom surfaces, the presence of bubbles, stripes and stains, scratches and abrasions), two signs for assessing smell (chocolate cocoa aroma and a complex of foreign tones), four signs for assessing taste (bitter, sweet, cocoa-fragrant aftertaste): four signs for assessing consistency (hard to bite, melting, fine and sticky). Each of the 14 signs was assessed on a conditional 5-point scale. The generalized results of the tasters' assessments served to construct profilograms.

Abroad, the profile method of tasting analysis was used until the 70s of the twentieth century mainly for analytical purposes in assessing the quality of products. With the development of marketing, this method began to be used in developing recipes for new products and assessing the competitiveness of food products. Currently, the profile tasting analysis method is used abroad:

For a comprehensive assessment of food quality;

To regulate vinification processes in accordance with the desired flavor and aroma profile of wines (USA);

Assessing the quality of complex products (chocolate, coffee, tea, sauces);

When developing new products by such companies as Nestle, Pepsico, Coca Cola, RC Cola, Sweppes, McDonalds, etc.;

In the development and evaluation of the taste and aroma profile of flavors by such companies as IFF (France), Quest (Netherlands), Dohler (Germany), Frutarom (Israel), Cargill (USA);

When compiling defectological maps of a food product;

When training tasters;

When monitoring the stability of the organoleptic characteristics of a food product;

When monitoring changes in the quality of a food product during storage and transportation;

When assessing consumer reactions and competitiveness of a food product, etc.

The proposed descriptor-profile method has great prospects in organoleptic analysis due to its flexibility and the ability to adapt it to solve various problems of a production or research nature.

Descriptor-profile method of tasting analysis as a marketing tool

The use of innovative tasting analysis techniques that ensure the development of high-quality, attractive and cost-effective products is currently relevant. In addition to the classic indicators characteristic of the food sector related to organoleptic evaluation, these techniques take into account a set of marketing parameters. For example, market price, product cost, its positioning, socio-demographic characteristics.

Sensory assessment can be used to position a product among analogues and assess its competitiveness, compare “old” products with new developments, and compare with competitors’ products. Consumer market research, consumer behavior studies along with market research.

Tasting a food product creates a connection between the product and the consumer through the latter’s sensory experiences. In this regard, the huge interest of marketing specialists in methods of tasting analysis, which can lift the veil of secrecy over the emotional perception of a particular product, is understandable. Along with quality assessment, the descriptor-profile method can also be successfully used in assessing the competitiveness of a food product; creating a successful brand; rebranding, which requires adjustment of the taste and aroma portrait of the product; development, modification and optimization of a new product; positioning the product among analogues; comparison with competitors' products; research of the consumer market and consumer behavior, pricing, assessment of the competitiveness of the brand. The algorithm for using DPM in marketing is presented in Fig. 1.

Thus, CSA as a tool for marketing food products is a set of interconnected processes that function to solve the main problem - meeting the population’s needs for high-quality and affordable food products.

CSA tasting analysis opens up extensive opportunities in the field of development, evaluation and marketing, as it allows you to express the qualitative characteristics of a product quantitatively in a clear and simple form.

Currently, the profile method of tasting analysis is used mainly to assess the quality of food products, mainly of complex composition. Tasters accustomed to the point method use the profile method very limitedly, considering it quite complicated. Unlike Russia, this method is considered the most promising abroad and is widely used.

The proposed descriptor-profile method is a modification of the profile method of tasting analysis.

Descriptor-profile method (DPM) is a method of quantitatively displaying the totality of the most significant organoleptic characteristics of a food product in the form of graphic profilograms, using pre-selected descriptors.

Thus, qualitative individual indicators related to taste, olfactory or tactile stimuli can be expressed quantitatively. According to the author, this methodology, supplemented by the practical skills brought to it, is necessary when developing new food products, including those with specified properties.

The descriptor-profile method has several areas of application. For example, it can be used in the product development and optimization phase, for standards development, quality assurance and control, and for research into the relationships between instrumental and sensory measurements.

In Fig. Figure 2 presents the scope of application of the descriptor-profile method of tasting analysis (DMA) based on the study of domestic and foreign literature.

Rice. 1. Model for the formation of consumer-oriented products

Rice. 2. Scope of application of the descriptor-profile method of tasting analysis

The descriptor-profile method plays an important role in the product life cycle. At the stage of developing new products, selected groups of respondents representing the target market segment express an opinion on the need for a new concept and its potential market prospects. Then comes product development and optimization. Sensory assessment is a useful tool for gaining and maintaining a sustainable position in the market. When a product has already established a strong position in the market, sensory evaluation can be a useful tool in the development of new products.

Bibliographic link

Chugunova O.V. SCIENTIFIC REVIEW: SENSORY ANALYSIS AND ITS IMPORTANCE IN ASSESSING THE QUALITY AND SAFETY OF FOOD PRODUCTS // Scientific review. Technical science. – 2016. – No. 3. – P. 118-129;
URL: https://science-engineering.ru/ru/article/view?id=1096 (access date: November 24, 2019). We bring to your attention magazines published by the publishing house "Academy of Natural Sciences"

Non-state educational institution

Central Union of the Russian Federation

SIBERIAN UNIVERSITY OF CONSUMER COOPERATION

Transbaikal Institute of Entrepreneurship

Department of Commercial Merchandising

SENSORY ANALYSIS OF FOOD

PRODUCTS

Training program

Specialty 080401.65 Commodity research and examination

(Standard training period is 5 years)

The program was compiled by Ph.D., Associate Professor of the Department of Commercial Merchandising ZIP SibUPK in accordance with the requirements of the State educational standard of higher professional education and the recommendations of the educational educational institution in the specialty 080401.65 Commodity research and examination of goods.

Reviewer: Ph.D., Associate Professor of the Department of Commercial Merchandising.

© , comp., 2011

© ZIP SibUPK, 2011

1. ORGANIZATIONAL AND METHODOLOGICAL

BASICS OF TRAINING

1.1. The purpose and objectives of the discipline, its place in the educational process

“Sensory analysis of food products” is one of the stages in the study of issues related to the basics of commodity science, which allows a more objective assessment of the quality of goods using the organoleptic method.

The purpose of the discipline is to obtain general information about the science of organoleptics, the characteristics of sensory analysis as a component of food quality, the study of components and sensory properties of products, and the development of tasting analysis methods.

To achieve this goal, it is necessary to solve the following tasks: mastering the skills of identifying food products, studying methods for researching food products, applying the acquired knowledge in practice.

It is important for a student to be able to determine the level of quality of food products using the simplest, most accessible methods, and to study the features of expert methodology in tasting analysis. It is indisputable that a businessman in any situation will need deep knowledge of those aspects of the product that are necessary in the modern market.

As a result of studying the discipline, the student must acquire knowledge of the national laws of the Russian Federation, regulations that take into account the regulatory framework of the European Union and other countries. The identification of certification objects introduced by the Federal Agency for Technical Regulation and Metrology is carried out by experts mainly based on organoleptic indicators. Organoleptic identification of a product must be carried out using scientifically validated sensory analysis methods in order to achieve the desired effect. When conducting sensory analysis, the professional knowledge of an expert taster who knows modern methods of organoleptic testing of food products is of great importance.

1.2. Requirements for the level of content mastery

disciplines

According to the requirements of the State educational standard

The specialist should know:

· methodology for conducting sensory analysis methods;

· general rules for conducting tastings.

The specialist must be able to:

· analyze and work with regulatory documentation and legislative acts;

· carry out sensory analysis of food products.

The specialist must have the skills:

· in the range of organoleptic quality indicators of products;

· in the psychophysiological foundations of organoleptics;

· in expert methodology in tasting analysis.

2. SCOPE OF DISCIPLINE AND TYPES OF TRAINING

WORK ACCORDING TO FORMS AND DURATIONS OF TRAINING

2.1. Thematic course plan for students

Full-time study, duration of study - 3 years

Name of sections and topics		Classroom classes, incl.
	practical
Topic7. The relationship between organoleptic and instrumental quality indicators

2.2. Thematic plan of the discipline for students

correspondence course, duration of study - 3.5 years

Name of sections and topics		Classroom classes, incl.
	practical
Topic 1. General information about science
Topic 2. Sensory characteristics as a component of quality
Topic 3. Components and sensory properties
Topic 4. Psychophysiological foundations of organoleptics
Topic 5. Methods of tasting analysis
Topic 6. Expert methodology in tasting analysis.
Topic 7. Relationship between organoleptic and instrumental quality indicators
Topic 8. Organization of modern tasting analysis

3.1. Topics and summary

Topic 1. General information about the science of organoleptics

History of the development of science - organoleptics, outstanding scientists who were involved in the selection of tasters to assess the quality of food products. Development of organoleptics abroad. Basic human sensory analyzers. Connection of science with other disciplines.

Topic 2. Sensory characteristics as a component

product quality

Indicators of quality of food products. Nomenclature of organoleptic quality indicators, carried out using the sensory organs of a taster without the use of measurement methods.

Topic 3. Components and sensory properties of products

Substances that cause coloring of products. Food pigments: oxygen-free carotenoids, oxygen-containing carotenoids. General information about food coloring. Color correcting and whitening agents.

Aroma-forming (flavor-forming) and flavoring substances. Evaluation of smell and taste. Food flavorings. Intensifiers (amplifiers) of taste and aroma. Flavoring substances. Smoked meat flavor and other flavor-forming compounds. Consistency and other indicators perceived by the senses of touch. Product consistency improvers.

Topic 4. Psychophysiological foundations of organoleptics

The nature and factors of visual sensations: color background, brightness of light and lighting.

Olfactory and gustatory sensations, their features, types. Perception of smells. Main types of taste. Influence of factors on taste and olfactory sensations. Individual sensitivity to smells and tastes. Memory and representation of odors. Compensation for odors and tastes. Taste illusions. Influence of external factors.

Tactile and other sensory sensations: touch by palpation, kinesthesis, hearing.

Topic 5. Methods of tasting analysis

Methods of consumer assessment. Analytical methods of organoleptic analysis: discriminative methods, paired comparison method, triangular method, “duo-trio”, ranking, profile, dilution index method, scoring, etc.

Point scales. Traditional point scales. Prospective scoring scales. Unified point scale.

Topic 6. Expert methodology in tasting

analysis

Formation of an expert group. Application of expert methods in profile analysis. Application of expert methods in the development of scoring scales.

Topic 7. The relationship between organoleptic and

instrumental quality indicators

Subjective and objective methods of quality assessment. traditionally divided into objective and subjective. Sociological, expert and sensory methods. Experimental and computational methods. Correlation between organoleptic and instrumental indicators of product texture.

Topic 8. Selection and training of tasters

Taster testing. Learning concepts: detection threshold, recognition threshold (identification), differential threshold, individual reproducibility of assessments, sensory memory, sensory minimum.

Testing the color sensitivity of tasters. Testing the olfactory organ. Testing taste sensitivity. Testing the tactile sensitivity of tasters. Reproducibility test. Testing the intellectual and professional competence of tasters. Certification of tasters. Training of specialists in sensory analysis of food products.

Requirements for the premises and equipment for conducting organoleptic analysis.

BIBLIOGRAPHICAL LIST

Legislative acts and other regulatory documents

1. Russian Federation. Laws. On the protection of consumer rights [Text]: [federal. Law: adopted by the State Duma on February 7. 1992]. – M., 1992.

Main literature

2. Duborasova, T. Yu. Sensory analysis of food products. [Text]: wine tasting: textbook. allowance / . – M.: Marketing, 2007. − 184 p.

3. Rodina, T. G. Sensory analysis of food products [Text] / . – M.: Academy, 2004. – 208 p.

4. Poznyakovsky, V. M. Expertise of drinks [Text] /, etc. - Novosibirsk: Sibirsk Publishing House. University, 2002. – 154 p.

Educational and program publication

ShevelevaOlga

Sensory analysis

food products

Training program

Specialty 080401.65 Commodity research and examination

goods (in the field of commodity research, examination and evaluation

goods in domestic and foreign trade)

(normative training period is 5 years)

License LR No. 000 dated April 19, 2000. Signed for publication on November 3, 2011

Business Xerox paper. Times New Roman typeface.

Format 60´84 1/16.Cond. oven l. 0.7. Circulation 10 copies. Order No. 000.

Printed in the printing house of the Transbaikal Institute of Entrepreneurship

Siberian University of Consumer Cooperation

Topic No. 1 Sensory (organoleptic) analysis

General characteristics of organoleptic analysis and its purpose

Organoleptics is a science that studies the properties of food products in their industrial forms and ingredients that cause a human sensory reaction.

Organolectics is the science of the sensory properties of media and ingredients and their measurements using human sensory organs, biological objects and artificial systems.

There are qualitative and quantitative organoleptic analysis. Qualitative analysis of an object is used to characterize the manifestation of its properties without their quantitative assessment. Quantitative analysis is intended to quantify the strength of expression of properties and is based on the quantitative characteristics of a person; it is carried out only by experts. The main purpose of quantitative analysis is to check product compliance with technical regulations, determine the level of product quality, determine product safety and damage.

Classification of types of organoleptic analysis and their characteristics

The main types of analysis are determined by a combination of senses (vision, hearing, taste, smell, touch, intuition). The following types of organoleptic analysis are distinguished: visual, olfactory, gustatory, tactile.

The visual method is used at the first stage of analysis as a non-destructive control method, it is the most sensitive method, and is used to characterize shapes, sizes, etc.

The quantitative characteristics of taste analysis are the sensation threshold, the recognition threshold, the discrimination threshold, and the saturation threshold. The intensity of taste is expressed in points, taste persistence. Adaptation is the time during which taste sensitivity begins to decrease.

Tactile organoleptic analysis

Touch – perception of texture, shape, size, mass, consistency, pressure, temperature. There are 3 types of tactile receptors:

1) Reacts to touch – unstable deformation.

2) Reacts to pressure - static deformation.

3) React to vibration - pulsating deformation.

Texture– macrostructure of the object (hard, fibrous, sticky, brittle, crumbly, homogeneous, inhomogeneous, rough, etc.).

Elasticity– a characteristic of texture determined by the speed and degree of restoration of the original dimensions after deformation.

Plastic– the ability to maintain deformation without destruction after the cessation of impact.

Fragility– ability to collapse during deformation.

Consistency– a set of texture properties that characterize its rheological properties, liquid, solid, gaseous. The texture includes mechanical characteristics (associated with force), geometric ones, characterizing the macrostructure.

Organization of sensory research

To obtain the optimal effect from the use of organoleptic methods for assessing the quality of goods, it is necessary to have qualified tasters; the assessment of the professional suitability of tasters is carried out based on the specifics of the task. Sensory sensitivity is divided into 4 groups: sensitive, average, satisfactory, low. To work as tasters, persons with satisfactory sensitivity or higher are selected.

Professional selection of tasters is a system of measures aimed at identifying the individual, personal and interpersonal qualities of a person for his successful activities.

The assessment is carried out in 3 stages:

1) Clinical trials.

2) Assessment of sensory sensitivity.

3) Psychological tests.

When testing for taste color blindness, the test subject is offered samples of basic tastes (a model solution with a sufficiently high content of substances that he must recognize).

To test olfactory ability, the following solutions are used:

The sensory sensitivity of the senses and smell is tested for recognition and discrimination. To determine recognition sensitivity, the following solutions are used:

To determine olfactory sensitivity, the following are used:

To determine the distinctive and recognition taste sensitivity, different concentrations of these or other substances are used and gradation is also carried out on a 4-point scale.

Formation of groups of tasters includes 4 stages: selection, theoretical preparation, training, testing. To evaluate the work of tasters, the repeatability index is used; it represents a statistical value of the correctness of the assessment when analyzing and using point scales and expresses the average deviation of the assessment results during repeated testing of the same products.

The professional awareness of the taster should include relevant knowledge of the commodity expert, production technology, storage of products, as well as knowledge of the factors influencing sensory research, methods of developing sensory abilities, their application and knowledge of the possibilities of suppressing subjective factors. The training of selected persons consists of theoretical training and a practical part. Selected, trained and trained tasters must undergo regular checks to ensure the reliability of the results.

From the selected candidates, tasting commissions are formed, which can be production or research. Production facilities identify and reject a low-quality product, as well as establish the causes of its occurrence and take measures to eliminate the causes (tasters must have average sensitivity, level 2). Research commissions determine the relationship between individual quality indicators, improve analysis methods, and solve other scientific problems (sensitivity level of at least 3). As a rule, the commission consists of 5-9 people headed by a chairman. When working with the commission, tasters must be guided by instructions developed for a specific case, containing an evaluation table, a verbal description of each level of product quality, and an analysis technique. Each taster evaluates the products individually in a specially equipped laboratory, the results of the work are entered into tasting sheets, and the results of the group’s work are summarized in a protocol for processing the tasting sheets. The results of the work of the tasting commission are expressed in points as the arithmetic mean value assigned to each sample. The reproducibility of test results is characterized by repeatability and comparability.

Repeatability– a quantitative expression of the magnitude of random errors of the tasting commission, when it has the same composition, under the same test conditions, and on the same day receives different results for assessing the same product sample.

Comparability– a quantitative expression of the magnitude of random errors that arise when different commissions obtain different results for the same sample under similar test conditions.

Sensory analysis methods

1) Preferences– is based on a logical conclusion and is used for consumer evaluation of goods, in this case the respondent answers the question whether he likes or not the product being offered. This method uses a scale: I like it very much, I like it, I don’t like it very much, I don’t like it very much. To obtain more accurate answers, questionnaires are used. These methods are used by specialists, as well as non-professionals.

2) Comparison methods, allow us to determine the differences between several samples, as well as the magnitude and direction of these differences. Methods can be symmetrical or asymmetrical (different numbers of sample units).

3) Paired comparison method, is that subjects are given two samples. It is necessary to establish the difference between them or which test is more intense and preferable. The method is simple and does not require a large number of samples.

4) Triangular comparison method, the taster is provided with three samples, which include two identical samples and one different one.

5) Two-pair method, the taster is provided with two unknown samples and a standard; it is necessary to select a sample that corresponds to the standard.

6) Tetraide method, uses four samples, which in pairs differ slightly in orgonoleptic properties, you need to choose the best sample.

7) Arrangement method, presupposes the presence of three or more samples and the taster must arrange the randomly served samples in order of increasing intensity or decreasing of any property (when studying the effect of changing the recipe on some indicators of product quality).

8) Dilution method, the liquid product is subjected to a series of dilutions until a concentration is obtained at which the studied characteristics are not detected orgonoleptically, and the intensity of the characteristics is assessed by the number of dilutions. When studying the performance of dense products using this method, extraction can be used.

9) Scoring methods, the results of product evaluation are expressed in terms of dimensionless numbers called points, the totality of which in a certain range forms a point scale. There are four types of scales: nominal, ordinal, interval, rational.

10) Profile method, each of the organoleptic properties is assessed by tasters according to the quality of intensity and the order of identification. The taste profile of beer is assessed as follows: aroma: hop, fruit, yeast, sour, malty, resinous, finyl acetic acid; goodies: salty, sweet, sour, fruity, bitter, yeasty, malty, finyl acetic acid, astringent;

Bouguer-Lambert-Beer law

Bouguer-Lambert-Beer law: the optical density of a solution is directly proportional to the concentration of the light-absorbing substance, the thickness of the solution layer and the molar light absorption coefficient.

E is a constant value for a specific substance that does not depend on the concentration and intensity of the incoming light flux, but depends on the wavelength. The graphical dependence of the optical density A of a solution on the wavelength of light is called the absorption spectrum.

The optical density of the solution is measured using photoelectrocolorimeters (PEC). And spectrophotometers.

The operating principle of the FEC is that the light flux passing through the cuvette with the solution hits the photocell, which converts the light energy into electrical energy measured by a microammeter.

Single-beam FEC diagram:

FEC operation: the diaphragm is adjusted so that the microammeter needle deflects across the entire scale to division 100 (cuvette with a pure solvent). Without changing the diaphragm opening, a cuvette with the analyzed colored solution is placed, while the microammeter needle shows the light transmittance (T, %), which is transferred to the optical density.

A=-log T T=I t /I o

To measure light absorption, select the wavelength at which the minimum detection limit is possible.

FECs are equipped with a special cassette with light filters; the light filter used must transmit rays of such length that they are absorbed by the analyzed solution.

The optical density A of the analyte can be measured sequentially using all filters and selecting the one with the highest optical density.

Analytical tasks, solved by photometric methods:

1) Determinations based on the substances’ own light absorption (determination of caffeine in tea).

2) Determination associated with the formation of intensely colored products when adding a colorless reagent to a colorless solution of the substance being determined (determination of proteins, nitrites).

3) Determinations based on measuring the color intensity of an excess of a colored reagent (determination of sugars by excess potassium dichromate).

Spectrophotometer diagram:

Spectrophotometry is based on the same laws of light absorption as photoelectrocolarometry. The ability to measure optical density of both visible and near UV and IR light. Accurate results are obtained when the optical density is approximately equal to 0.4, and if the OD is 0.8 or more, then cuvettes with a shorter length are used, if the OD is 0.1, then cuvettes with a longer length are used.

Fundamentals of Spectroscopy

Spectroscopic method is a method based on the interaction of matter with electromagnetic radiation.

Electromagnetic radiation is a type of energy that travels in a vacuum at a speed of 300,000 km/s and which can appear in the form of light, thermal, UV radiation, micro-, radio waves, gamma and x-rays.

The properties of electromagnetic radiation are described based on theories of its wave and corpuscular nature.

To describe the phenomena of absorption and rejection of electromagnetic radiation, it is necessary to use ideas about its corpuscular nature. In this case, radiation is represented in the form of a stream of individual particles - fatons. The energy of such a particle is in strict accordance with the frequency of radiation.

Atomizers

The simplest way to transform a sample into an atomic state is through a flame. Subsequently, to improve the sensitivity of determination, an electrometric method of atomization was proposed - graphite furnaces.

With the flame atomization method, the sample solution is sprayed into the flame in the form of small drops; the combustible mixture to support the flame consists of a combustible gas and an oxidizer gas.

The oxidizer can simultaneously serve as an atomizing gas or be supplied to the burner separately (auxiliary gas); to determine most elements, an acitylene-air mixture is used; evaporation components of the sample, their dissociation to free atoms, excitation atoms under the influence of external radiation, ionization atoms. The same processes occur in other types of atomizers.

Electrothermal method atomization - using graphic tubes heated by electric current (graphite cuvettes). The length of the tube is 30-50mm, the internal diameter is about 10mm.

A sample flow rate of approximately 10 μl is introduced into the cuvette and heated according to a special temperature program by applying voltage through metal contacts (up to 3,000 degrees Kelvin), by programmably increasing the temperature to 100-110 o C, the sample solution is first dried in a protective atmosphere of inert gas (orgone), then the sample is ashed raising the temperature to 500-700 degrees during the ashing process, volatile components are removed, then the temperature is increased to 2-3 thousand kelvin, while the processes of dissociation, excitation, etc. described above occur.

Monochromator

The role of the monochromator in AAS. It consists of cutting off excess emission lines of a hollow cathode lamp, molecular bands and extraneous external radiation. Due to too wide spectral passbands, the use of light filters in AAS is not possible. Typically, for monochromatization in AAS, diffraction gratings containing up to 3 thousand lines per millimeter are used, and photomultipliers are used as radiation receivers.

A faton hits the cathode and knocks an electron out of it; an electric current arises in the vacuum space between the cathode and anode. An electron ejected from the cathode bombards the dynodes closest to it and knocks out several secondary electrons from it, which in turn bombard the next dynode. As a result, the number of knocked out electrons increases like an avalanche.

Quantitative analysis according to the Bouguer-Lambert-Beer law.

Practical use: The AAS method can determine up to 70 metals; non-metals, as a rule, cannot be directly determined; there are methods for indirect determination of non-metals; the AAS method can determine both trace and fairly high contents.

Disadvantages of AAS: single-element analysis method (requires a new hollow cathode lamp), a drum with lamps is installed for faster determination.

Quantitative Analysis

Quantitative analysis. A special feature of the RPA method is the presence of strong matrix effects. In addition to the direct excitation of the atoms of the element being determined by primary X-ray radiation, a number of other phenomena can be observed. Interactions of radiation with matter: excitation of atoms of the element being determined under the influence of secondary radiation from atoms of matrix elements; absorption of primary radiation by matrix elements - the intensity of the exciting radiation decreases and the analytical signal decreases; absorption of secondary radiation by matrix atoms 9 underestimation of the analytical signal). Methods for correcting matrix effects:

1) Use an external sample standard that matches the sample being analyzed as closely as possible. In this case, matrix effects affect the counting rate equally for both the sample and the standard.

2) Special sample preparation - the sample can be greatly diluted with a weakly absorbing material, sucrose or cellulose, the influence of matrix effects is greatly reduced.

3) Calculation method - the use of theoretical concepts about the interaction of matter with X-ray radiation.

Practical use

Practical use. The XRF method is used to determine the main components in the analysis of materials in the metallurgical, construction, glass, ceramic, fuel industries, geology, and, more recently, for the analysis of environmental objects in medicine and scientific research purposes. The RPA method can determine 83 elements from fluorine to uranium. Analyze solid samples - powdery, glassy, ​​metallic.

Powders must have a grain size of less than 30 micrometers to ensure reproducibility and are pre-compressed into tablets without filler or mixed with pulp or graphite. To homogenize the sample, melting is used, fused with sodium or lithium to a glassy mass. Metal samples are analyzed as is.

The main advantage of the RPA method is the possibility of non-destructive testing; it is convenient for analyzing the near-surface layer of materials and works of art. Prototype spectrometers are available that can be easily transported to the object being analyzed.

Radiation sources

Hot solids are used as radiation sources in the IR region. For such sources, the distribution of radiation intensity along lengths. The waves depend on temperature and are described by Planck's law. This distribution is not uniform and has a clearly defined maximum. For ICS, it is necessary to cut off intense short-term radiation in the visible region and leave longer wavelength and less intense radiation in the IR region.

The most common sources of IR radiation are Nerst pins, made of yttrium and zirconium oxides, as well as silicon corbide.

They are heated to high temperatures using electric current (800-1900 o C).

For the far-IR region, special radiation sources are used - high-pressure mercury discharge lamps. In the near field, you can use incandescent lamps with tungsten filament.

Sample preparation

Sample preparation is labor-intensive compared to other spectral methods. For gaseous samples, special evacuation is used (thickness from mm to m). Most often, liquid samples are analyzed, and neither water nor alcohol are suitable as a solvent. Organic solvents purified from water are used. The following solvents are used: nujol, acetone, benzene. To ensure that the solvent absorbs itself, thin cuvettes (up to 1 mm) are used as little as possible.

Solid samples are analyzed directly if the material can be prepared into a thin layer

The powdered sample is mixed with nujol until a homogeneous mixture is placed between the two windows of the cuvette. The windows are pressed against each other, getting rid of air bubbles.

Monochromators

In ICS, both prisms and diffraction gratings can be used as monochromators. Depending on the spectral range being studied, prisms made of quartz, LiF, NaCl, KBr, CsI are used. Currently, grating monochromators predominate. Advantages:

High uniform resolution,

Mechanical and chemical resistance,

Wide operating spectrum range.

Detectors

Thermocouples are used as detectors. The thermocouple converts the energy of infrared radiation into heat and then into electricity. The resulting potential difference is recorded in the usual way.

The balometer works on the principle of a resistance thermometer. The working material is a metal or alloy (platinum, nickel, etc.), the electrical resistance varies greatly with temperature.

A common problem in measuring IR radiation intensity is the presence of significant environmental thermal noise with a small useful signal. Therefore, IR radiation detectors isolate as much as possible from the environment.

IR spectrometer device

As a rule, an IR spectrometer operates according to a 2-beam scheme: 2 parallel light streams are passed through a cuvette with an analyzed sample and a comparison cuvette - this reduces errors associated with scattering, reflection and absorption of light, the cuvette material and the solvent. The light emitted by the source is divided into 2 streams: one of which passes through the measuring cell, and the second through the comparison cell. Then both flows fall on a mirror rotating with a certain frequency, this mirror is divided into 4 equal sectors (90 each), 2 of them are transparent, and the other 2 are reflective. Light fluxes alternately fall on monochromats (according to Littrov’s scheme). The light beam is reflected by the Littrow mirror and passes through the prism twice. Then, using a system of mirrors, it is directed to the detector. The spectrum is scanned by rotating the Littrow mirror or prisms. A highly sensitive thermocouple is used as a detector. The electrical circuit of the amplifier is assembled so that at the same intensities of the measured light flux and the comparison flux, the resulting current is zero. When light is absorbed in the cell being measured, the intensity of the corresponding light flux decreases. This causes an electric current to appear in the circuit, which drives the motor. The motor moves the attenuator wedge into the reference light stream enough to equalize the intensity of both signals again, so the position of the wedge characterizes the degree of light absorption. At the same time, information about the position of the wedge is supplied to the recording device. Data on the current wavelength is determined by the position of the Littrow mirror.

IR spectrometer with Fourier transform (on your own, will not be used in the exam).

Qualitative analysis

Qualitative analysis is used to solve various types of problems. The IR spectrum allows one to establish the nature of a substance by comparing the experimental spectrum of an unknown substance with the spectra available in the spectral library. The IR spectrum allows you to find out whether the structure of a substance corresponds to the proposed formula, and also to select the most probable one among several structures. We can guess the structure of the substance. When studying the structure of substances using IR spectroscopy, it is necessary to adhere to the following basic principles:

1) To record the IR spectrum, a pure substance should be used;

2) It is necessary to know additional information about the substance (what class of substances, etc.)

3) The absence of a band in a certain frequency range is reliable evidence that the corresponding structural fragment is absent in the molecule. However, the presence of a band does not yet indicate that the molecule contains this group.

4) For the group under consideration, all its characteristic spectral bands should be found

5) First of all, it is necessary to study the bands in those regions of the spectrum where there are few of them.

6) Reliable structure assignment is possible only when all characteristic bands have been identified and there is a spectrum of a similar constructed compound for comparison.

This method is most often used together or in combination with other methods.

Quantitative Analysis

For quantitative analysis, the mid-IR region is not as suitable as UV or visible. The intensity of radiation sources here is low. The sensitivity of the detectors is low. The difficulty is created by the very thin thickness of the cuvettes, which is difficult to reproduce or measure. The level of scattered radiation in the IR region is much higher than in the UV and visible. Careful calibration using standard samples, as well as the use of modern equipment, make it possible to overcome these difficulties to some extent and use IR spectroscopy for quantitative analysis. Using this method, individual aromatic hydrocarbons, glucose in blood serum, and air pollutants (CO, acetone, ethylene oxide, chloroform) are determined. The near-IR region is of great importance for IR analysis. Near-infrared spectroscopy can directly determine the octane number of gasoline.

Optical microscopy

A microscope is an optical instrument for obtaining magnified images of objects.

The microscope consists of two systems: an eyepiece and a lens. The lens is positioned close to the sample (epsilon). Creates the first enlarged image of the object (epsilon '). This image is magnified 2 times or more to the eye of the beholder epsilon." An epsilon """ image is formed on the retina at a significantly larger angle, which determines the high magnification of the microscope.

1677 The microscope was invented, Livenhoek saw the simplest organisms for the first time, and looked at a sample of water from a ditch. Modern microscopes use complex optical systems, and also create special conditions for illuminating objects. As a result, such a microscope can magnify several thousand times. N opt is approximately equal to 10*10*10.

If an object is illuminated with ordinary white light, the image of the object will not be sharp. In a lens system, optical beams of rays of different colors do not coincide, they have different paths, as a result, the image for each wavelength is shifted, since the optical system decomposes white light into a spectrum. As a result, small details become indistinguishable. To organize monochromatic illumination in microscopes, special lamps and optical filters are used. The closest thing to monochromatic light of one wavelength is the radiation of some lasers. Even in the case of monochromatic illumination, there is a limit to the resolution of the microscope; this limit is determined by the wave nature of light, which manifests itself in the diffraction of the light wave at the edges of the lenses of the optical system.

Drawing. A – general view of the diffraction pattern when observing two small objects at a small angular distance. B – limit of resolution of two points according to Rayleigh.

In optical microscopy, the concepts of limiting resolution angle and resolving power are used to characterize the magnification capabilities of actual microscopy. The limiting angle of resolution is the angle at which the first dark part of the diffraction pattern passes through the light center of the second, depends on ƛ of the illuminating object, and the minimum distance resolved by the microscope is determined by the formula:

A – numerical operation. A≤1, depends on the material and material of the lens.

The resolution of a microscope is the reciprocal of the maximum resolution angle. Rayleigh's rule - the maximum resolution of an optical microscope cannot be more than half the wavelength of light illuminating the object.

Electron microscopy.

It was invented in the 1930s, in order to increase the resolution, it was proposed to use photon radiation (electron flow) instead of light radiation, the wavelength of which is determined by the formula:

ƛ=h/mv – De Broglie wavelength.

h – 6.624*10 -24 J*m

m – 0.9*10 -27

v is the speed of the electron.

The maximum resolution of electron microscopes is 1000 times greater than that of optical microscopes. In order to obtain an image in a microscope, a stream of electrons emitted by a hot cathode is used. Electrons are controlled using external electromagnetic fields. An electronic image is formed by electric and magnetic fields in the same way as a light image by optical lenses. A device for focusing and scattering an electron beam is called an electron lens. Since the eye cannot directly perceive electron beams, they are directed to luminescent monitor screens. Individual atoms can be seen. The most widely used scanning microscope (SEM). In such a microscope, a thin beam of electrons with a diameter of 10 nm scans the sample along horizontal lines and synchronously transmits a signal to the monitor, similar to the operation of a TV. The source of electrons is metal (tungsten), from which, when heated, electrons are emitted - thermionic emissions. The need to work in complete vacuum, since the presence of gases inside the chamber can lead to its ionization and distort the results. Electrons have a destructive effect on some things. It allows you to see the atomic lattice and distinguish an atom, but its resolution is not enough to see the atomic structure or the presence of chemical bonds in the molecule. Neutron microscopes are used for this purpose.

Neutron microscopes. Neutrons are included together with protons, are part of atomic nuclei and have a mass 2000 times greater than electrons. The resolution is 1000 times higher than that of electron microscopes. The main disadvantage is that neutrons cannot be controlled by electromagnetic fields, so it is very difficult to build them.

Atomic force microscope

Atomic force microscope (1986), similar to the operating principle of a tunnel microscope. Measures the bonding strength of atoms. The approach of the needle leads to the fact that the atoms of the needle are increasingly attracted to the atoms of the sample, the force of attraction will increase until the needle and the surface get so close that their electron clouds begin to repulse electrostatically; with further approach, the electrostatic repulsion will exponentially weaken the force of attraction. These forces are balanced at a distance of 0.2 nm between atoms. A diamond tip with a radius of curvature of less than 10 nm, mounted vertically at the end of a horizontal plate - cantilever, is usually used as an AFM probe.

The tip of the scanning needle is called tip, and the console is called cantilever. When the force acting between the surface and the tip changes, the console bends and this is recorded by a sensor (laser beam). The laser beam is reflected onto a photodiode, and the readings are then transmitted to a computer. The advantage is the ability to study the structure of electrically conductive samples and non-electrically conductive materials.

Types of AFM:

1) Magnetic force microscope, a magnetized tip is used as a probe. Its interaction with the sample surface makes it possible to record magnetic microfields and present them in the form of a magnetization map.

2) An electric force microscope, the tip and the sample are considered as a capacitor, and the change in capacitance along the surface of the sample is measured.

3) Scanning thermal microscope. Records temperature distribution over the surface of the sample, resolution reaches 50 nm.

4) Scanning friction microscope. The probe scrapes along the surface, leaving a map of frictional forces.

5) Magnetic resonance microscope.

6) Atomic force acoustic microscope.

No. 4 Physical research methods.

There are electrophysical and thermal methods.

Double probe method

Used to determine the resistivity of samples of regular geometric shape with a known cross-section, for example: used to monitor the distribution of ρ (resistivity) along the length of ingots of semiconductor material. The range of measured values ​​is 10 -3 to 10 4 ohm*cm.

When using the two-probe method, ohmic contacts are made on the end faces of the sample, through which an electric current is passed along the sample; two contacts in the form of metal probe needles are installed on one of the surfaces along the current line, having a small contact area with the surface, and the potential difference between them is measured. If the sample is homogeneous, then its resistivity is determined by the formula:

S – distance between probes.

A is the cross-sectional area.

I – current strength.

Current through the sample is supplied from a regulated constant current source. The current strength is measured with a milliammeter, and the potential difference with an electronic digital voltmeter with high input resistance. The condition for using the two-probe method for the quantitative determination of Po is the one-dimensionality of the spatial distribution of equipotential current lines (the presence of a resistance gradient across the sample and inaccurate adherence to geometric dimensions leads to an increase in the measurement error).

Four-probe method.