SENSORY EVALUATION OF MEAT AND MEAT PRODUCTS
Sensory evaluation of foods including foods refers to their scientific evaluation through the application of human senses (taste, smell, sight, feel and sound).
The importance of sensory analysis has grown over the years because human senses are biological detectors which can perceive odor, taste etc. even below the lowest limit of instrumental sensitivity. Moreover, instruments usually analyze only a single component at a time whereas the overall impression and taste of a food product can be properly assessed only by human sensory perception. Therefore, sensory evaluation is defined as a scientific discipline used to measure, analyze and interpret reactions to those characteristics of food as they are perceived by the senses of sight, smell, taste, touch and hearing.
Organoleptic vs Sensory evaluation:
The organoleptic tests are often subjective, with few tasters and the interpretations open to prejudice. However, the sensory tests are developed by scientists as a formalized, structured, and codified methodology. Traditional organoleptic testing is unsatisfactory for scientific purposes due to a number of insufficiencies. It seldom complies with principles of science, i.e. full objectivity and reproducibility; however, sensory evaluation is basically established on principles of science by using of human senses or instruments as scientific tools.
Selection of Taste panel:
Selection of taste panelists is very critical for obtaining reliable sensory data. Taste panel can be broadly divided into two categories i.e. Specialized panel and Consumer panel. The sensory testing of meat and meat products may be either consumer oriented or product oriented. Information on consumer likes and dislikes, preferences and requirements for acceptability can be obtained with the help of consumer oriented testing.
Consumer panel
Consumer panel may consist of 100 or more number of representative persons of the target population of potential product users. This testing can be done at any central location such as market, community centre, retail shop or at consumers’ homes. A true consumer panel requires selection of a panel representative of the target population which is both costly and time consuming. Therefore, in-house consumer panel usually consisting of 30-50 untrained panelists selected from the personnel working in the organization is used to represent the consumer panel for commercial practice.
Specialized panel
Specialized panel or product oriented panel testing uses small number of trained panelists who literally function as testing instruments. Such panelists can easily identify differences among similar meat products or intensities of flavor, texture, appearance etc. because they are selected on the basis of their sensory ability being specially trained for such a task.
On the basis of the training provided/required, the sensory panels are categorized either Trained or Semi-trained. The trained panelists are able to establish the intensity of sensory character or overall quality of meat and meat products. They are usually involved in all developmental and processing studies. Semi-trained panelists are persons normally familiar with the quality of different classes of meats and are in a position to discriminate differences and communicate their reactions. In a semi-trained panel, individual variations are generally balanced by involving greater number of panelists.
Sensory evaluation of food is necessary for:
- New product development
- Product improvement
- Quality control
- Assessment of process variation
- Setting standards
- Shelf life studies
- Market level consumer tests
- Correlating sensory evaluation with chemical, physical and instrumental measurements.
Evaluation of meat products can be done by:
- Taste panel evaluation.
- Measurement of sensory attributes with the help of machines like Instron, Warner-Bratzler, Shear force, etc. but human sensory perception is still preferred over machines.
Various methods used for sensory evaluation by taste panel:
1. Discrimination/Difference testing:
This method of sensory evaluation determines how the products are perceived and significance of difference between different products with respect to one or more sensory effects is judged. Commonly used difference tests are:
I. Triangle test:
This test involves presenting three coded samples to sensory panelists, where one sample is different from the other two samples. The panelists are asked to identify the odd sample. This testing method is often used as a tool in quality assurance programmes. This test is also used in product development studies to determine if various ingredient substitutions or changes in process will result in adverse product effects.
II. Duo-trio test:
This test provides the sensory panelists a one in two chance of identifying the correct sample. The panellists are offered one sample marked as control (reference) alongwith one or several pairs of samples and are asked to identify the sample which matches the control.
III. Paired comparison test:
In this form of sensory evaluation, a pair of coded samples is presented for comparison based on some specified characteristics.
Ranking test: This test is an extension of paired comparison test. In this test, panelists receive three or more coded samples and are asked to rank samples for intensity of some specific characteristics. Ranking tests are often used to screen one or two best samples from a group of samples rather than to thoroughly test all samples.
2. Descriptive methods:
It involves discrimination of qualitative and quantitative traits of a sample using trained taste panel. It determines the specific differences and how extreme are those differences. Descriptive analysis requires at least three evaluative processes:
- Discrimination of the trait.
- Description of the trait.
- Quantifying the trait.
Discrimination and description of the trait are qualitative. The language used is developed through careful training and practice with the panel. This requires panelists to develop a common vocabulary, which catalogues various sensory stimuli with appropriate language. Quantifying the trait relates to the overall intensity of the characteristics. Descriptive analysis is the only method that deals with the total picture or profile of a product. Commonly used descriptive tests are:
i. Flavor profile test:
The best known method of descriptive sensory analysis is flavor profile. This technique of sensory evaluation provides a detailed, descriptive evaluation of the quantitative and qualitative attributes of a flavor complex. The profile method concentrates on the entire flavor of a product and the individual attributes of a flavor in relation to each other. The dimensions of flavor analysis by the profile method include: i) perceptible aroma, taste, flavor and feeling factors (called ‘character notes’), ii) degree of intensity of each factor, graded on the following scale:
O = Not present
X = Just recognizable or threshold
1 or + = Slight
2 or ++ = Moderate
3 or +++ = Strong
iii) order in which these factors are perceived, iv) after taste, v) amplitude or overall impressions of aroma and flavor, graded on the following scale:
X = Very low
1 = Low
2 = Medium
3 = High
Flavor profile test utilizes a panel of 4 to 6 selected judges who first examine and then discuss the product in an open session. Once agreement is reached on the description of the product, the panel leader summarizes the results in a report form. Panelists are selected for training based on a series of screening tests including sensory acuity, interest, attitude and availability. The panel leader plays a key role in directing the conversation and providing a conclusion for the test. Panelists could be led to a conclusion without being aware that this had occurred. This test has to be carried out very thoroughly over a long period. Only repeated analysis (10, 15 or 20 times) with the same test product will provide uniform results by a whole panel.
ii. Texture Profile test:
Texture profile is defined as the sensory analysis of the texture complex of a food in terms of its mechanical, geometrical, fat and moisture characteristics, the degree of each present and the order in which they appear from first bite through complete mastication. Each texture term should be well-defined. For each parameter, a scale of 5, 7, 8 or 9 categories and for each category (of a scale) there is a specific product that represents the particular sensation. This is a descriptive method which includes description analysis from a structural point of view. By structure, we refer to the development of the descriptive terminology, the scales for recording intensities, and the word/product anchors for each scale category. Once this structure is completed, the product evaluation procedure follows the flavor profile approach with panelists discussing results in order to reach a conclusion.
iii. Quantitative Descriptive Analysis (QDA) method:
In QDA method of sensory evaluation, approach is primarily behavioural in orientation with considerable emphasis on the use of replication as a basis for assessing the quality of the output. The development of the method evolved from a member of major considerations to ensure that it would:
- Be responsive to all the sensory characteristics.
- Be a multi product test.
- Use a limited number of subjects (10-12).
- Use subjects who are qualified before participation.
- Employ a language develop process from leader influence.
- Be quantitative.
- Have a useful data analysis system.
- Have a data processing capability.
Application of descriptive analysis
- Monitor competition
- Storage testing
- Product development
- Quality control
- Instrument sensory relationships
3. Affective methods:
It evaluates preference and / or acceptance and / or opinion about the product. It can be used for consumer or trained panelists.
Many types of scales or scoring systems are used for preference evaluations. These may include structural word scales or graphics. In structural scales, a scale of 7 to 10 points is commonly used to avoid use of end points of the scale. Moreover, use of smaller scales does not allow the panelists to show degree of variation. Commonly employed affective methods are:
i. Hedonic test: This is the most simple and oldest method. The panel is asked to indicate which sample they preferred. This is the most commonly utilized test in assessing meat products.
ii. Ranking test: In this method, panelists are asked to order three or more samples for increasing or decreasing amounts of a specific attribute, overall quality or response on the same occasion.
Important sensory attributes for meat products:
1. Appearance and color:
Appearance is one of the most important factors which influence the consumers’ inclination while buying the fresh as well as processed meats. The appearance of meat surface to the consumer depends on the chemical state of myoglobin present in meat. The differences may also be due to species, breed, sex, age, type of muscle and training. In fresh meat, before cooking, the most important chemical form is oxymyoglobin. The final color of cooked meat is dependent to the pigment changes brought about by temperature, time and method of cooking. When meat is cooked, there is gradual change of color from dark red or pink to a lighter shade and finally at higher temperatures to grey or brown color.
2. Flavor:
Flavor is a complex sensation comprising mainly of odor and taste, odor being more important.It is sensed jointly by the oral and olfactory senses. There are four basic tastes viz. sweet, salty, sour and bitter (umami as fifth basic taste because of glutamate in food, is also included by some researchers). These basic tastes have their receptor taste buds or papillae on the tongue and upper palate. The sweet taste is most easily sensed at the tip of the tongue, the saline at the tip and edges, the sour at the edges and bitter at the back of the tongue. The papillae for bitter taste are especially deep, so the sensation takes longer to perceive and tends to linger. The odor and taste of cooked meat arise from water or fat-soluble precursors and by the liberation of volatile substances that exist in the meat. Odor is perceived at the regio-olfactoria which lies at the top of the inside of the nose. Meat samples should be smelled first followed by tasting for a rational and sound flavor perception of several volatile components present in meat.These components are significantly marked when meat is cooked.Flavor has been shown to have a profound effect on the overall acceptability of meat products.There is a gradual loss of flavor during storage; this may occur even in frozen conditions.Flavor of fresh raw meat is weak, salty and serum-like.Fresh meat fat also has almost indistinct taste and odor.It is during cooking that flavor gets pronounced and becomes meaty.
3. Texture and Tenderness:
Texture is one of the most important eating quality attributes in the acceptance of meat.The overall impression of texture is perceived by the senses of touch, sight and hearing.Texture is a direct consequence of the grain in fresh meat.Tenderness is the primary essential and one of the most important sensory attributes of meat.Tenderness is perceived as three components by the consumer viz. ease of initial penetration, the number of bites for complete disintegration of meat and the amount of residue left behind after complete chewing. Tenderness is influenced by the animal (age, sex, breed, and species of the animal), state of rigor of the meat, handling of the animal peri-slaughter, manner in which meat is handled (cold shortening, thaw rigor), ageing etc.
4. Juiciness:
Juiciness is perceived as two components i.e. the initial purge and sustained juiciness due to marbling. Juiciness is also influenced by the state of rigor of the meat, handling of the animal peri-slaughter, manner in which meat is handled (cold shortening, thaw rigor), ageing etc. Juiciness is a reflection of water holding capacity (WHC) of meat.
5. Mouth coating:
It can be defined as the residue left coating the mouth after swallowing certain meat products. It is affected by the chemical composition of the product like in buffalo meat products, mouth coating is due to higher fat contents which do not disintegrate completely during emulsion formation, resulting in larger fat particles which leave a film on the tongue and palate after swallowing.
6. Overall acceptability:
It refers to the sensory perception of meat product in totality. Though it is not a sensory attribute as such, it is of utmost importance because it is the overall acceptability of a product in absolute terms which actually matters. A meat product is not taken attribute-wise, so a cumulative impression which the product leaves on the sensory panelist is evaluated as overall acceptability. It should not be taken as sum average of all the attributes because some attributes influence the overall acceptability of the product more than others.