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Sensory Evaluation

Sensory Evaluation

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Sensory Evaluation

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    1. Sensory Evaluation A scientific discipline used to evoke, measure, analyze and interpret reactions to those characteristics of food and materials as they are perceived by senses of sight, smell, taste, touch and hearing. IFT; USA

    2. DEFINITIONS: A group of similar sensory impressions mediated by a given organ is referred to as sense (modality). Factors from the environment or from body biochemistry that elicit sensory impression are referred to as sensory stimuli A combination of sensory impressions is called a sensation.

    3. DEFINITIONS: An interpretation of sensation with reference to what has been experienced and learned by individual and the resultant overall impression is called sensory perception. The least stimulus energy capable of producing a sensation is called an absolute threshold

    4. DEFINITIONS: Detection threshold - the magnitude of stimulus at which a transition occurs from no perceived sensation to a perceived sensation (similar to absolute threshold). Difference threshold - the least amount of change of a given stimulus necessary to produce a change in sensation.

    5. DEFINITIONS: Recognition threshold - the minimum concentration at which a substance is correctly identified. Terminal threshold - the magnitude of a stimulus above which there is no increase in perceived intensity of appropriate quality for stimulus.

    6. FOOD PRODUCTS ARE MULTIDI- MENSIONAL: Visual: package appearance, product appearance, color. Olfactory: product aroma/fragrance. Kinesthetic/Tactile: product feel. Gustatory: product taste, texture. Auditory: sound from use.

    7. CAN WE DISCRIMINATE TWO STIMULI: The sensitivity of human senses is limited There are limits to the physical magnitude of stimulus - absolute sensitivity. There are limits to the magnitude of physical difference between two stimuli which can be perceived - differential sensitivity.

    8. Principles of sensory response behavior: The same stimuli may evoke a variety of sensory responses on different occasions. Two physically different stimuli can evoke two identical responses.

    9. EXPERIMENTAL MEASURES USED TO OVERCOME THIS PARADOXICAL SITUATION ARE AS FOLLOWS: Panelists are required to make a choice Reliance is placed on repeated measurements

    10. PSYCHOLOGICAL ERRORS AND PHYSICAL CONDITIONS: Error of central tendency. Time-order error. Error of expectation. Stimulus error. Logical and leniency error. Contrast and convergence errors. Proximity error. Suggestion effects. Motivation.

    11. SENSORY EVALUATION IS USED TO: Monitor formulation changes. Monitor processing changes. Monitor shelf-life changes. Guide product promotion. Determine consumer acceptance.

    12. INDUSTRY INTEREST IN SENSORY ANALYSIS IS OFTEN FOCUSED ON: How to connect consumer acceptance data to sensory and analytical data. How to determine the sensory strength and weakness of product. How to monitor panelists and evaluate panel training. How to understand cultural and other sources of differences in the use of rating scales. How to manage the vast amounts of sensory and consumer data typically generated.

    13. IN SENSORY EVALUATION: The aim is to discover something. It is best to have a repeated measuring design. A number of samples presented to judge is important. Judge should work individually. The rating may be influenced by a preceding stimuli. The rating of stimuli depends on the context. It may be difficult to produce physically identical samples.

    14. QUESTIONS ANSWERED BY SENSORY WORK: Is there a difference? Is the difference significant? How great is the difference? Is the product preferred? How acceptable is the product? What is the sensory description of the product?

    15. CONTROLS: Temperature. Lighting. Atmosphere -smell. Individual booths. Sample selection (identical code dates). Coding samples (3 digits codes). Sample preparation. Sample presentation. Subject selection.

    16. SENSORY EVALUATION STEPS: Define overall project objective Define test objective. Screening the samples. Designing the test (method and judges). Conducting the test. Analyzing the data Reporting the results.

    17. SENSORY METHODS ANALYTICAL TESTS Discriminatory tests Sensitivity tests AFFECTIVE TESTS

    18. SENSORY METHODS DISCRIMINATORY Simple Difference - which sample is different? Triangle test Duo-trio test Directional Difference - which sample is sweeter? Paired comparison test

    19. SENSORY METHODS-DISCRIMINATORY TESTS Directional Difference - which sample is sweeter? Ranking test Scoring or Scaling - how hard is the sample? how much the sample is liked/preferred? Hedonic scale Verbal scale Pictorial scale Graphical scale Ratio scale

    20. Ranking test Useful if we have more than two samples to compare as ranking test is a multi sample comparison test Sample may be ranked based on preferences, overall acceptability, or specific sensory attribute Ranking is a useful for a rapid screening of samples There are some constraints: Nature of sample impose a practical limit on a number of samples that can be evaluated (3-5 samples are optimal); the least sensitive method for statistical inference (conclusion) Samples are evaluated only in relation to each other, therefore results from one sets of ranks cannot be compared with the results from other set of ranks unless both tests contain the same samples

    21. Statistical analysis of ranking test data There are statistical tables that allows to analyze results based on sum of the ranks assigned for each sample by all panelists. These tables provide ranges of rank totals which are not significantly different. An experimental sample for which the rank total is outside of the range listed in the table is considered to be significantly different. ANOVA -analysis of variance wherein the ranks are converted to scores. For 4 samples test first-1.03, second - 0.30, third - (-0.30) and fourth - (-1.03).

    23. Situation exercise II

    24. Situation exercise III

    25. Situation exercise IV

    26. Interpretation of scaling sensory responses: The interpretation of data based on a simple arithmetic averages is statistically invalid if: the descriptors deviated from an equal partitioning of linear scale the meaning of various descriptors was not clear to all panelists

    27. Magnitude Estimation Ratio-scaling method First presented sample has assigned arbitrary score (eg 10 or 50). Panelist may be asked to assign own score The other samples are compared to the initial one. If the intensity of the designated attribute appears twice as high then the assigned score should be twice that given to initial sample

    30. Data treatment Calculate geometric mean of scores for each level of stimulus logarithmic transformation of both geometric mean score and stimulus levels Subject data to linear regression in order to calculate intercept and slope values Present data on a logarithmic plot.

    31. Data treatment Log S = nlog C + log k S = kCn where S geometric mean of sensory score; C- level of stimulus n deal with the way we transform the ratio of stimulus levels to ratios of sensory magnitudes n>1 sensory ratios greater than physical ratios n<1 sensory ratios lower than physical ratios

    33. Descriptive tests The purpose is to provide as much information about the flavor/texture of food as can be stated in words and/or numbers Each evaluate sensory property must be recognized, scaled when applicable and communicated Panelists are carefully selected and thoroughly trained.

    34. Descriptive tests Flavor profile Quantitative descriptive analysis Texture profile

    35. Flavor Profile Aroma and taste dimensions are evaluated separately 5-6 highly qualified panelists meet to develop a proper terminology for referring to the various flavor notes associated with the product. Each flavor note and its verbal description must perfectly clear to all panelist panelists evaluate product individually each panelist observations are reported to panel leader members of panel are holding discussion to identify and solve problem that may have cause variations

    36. Each panelist is asked to provide the following information Flavor character notes (taste and aroma separately) The order of appearance of each flavor note. The intensity of each flavor note using a structural scale any perceived aftertaste total flavor intensity amplitude (overall flavor intensity)

    37. Panel leader responsibility is: To select the products that will be evaluated in each session To facilitate the discussion and to assist where there is a conflict or disagreement about particular wording to record the discussion to keep dialogue to be focused on the task to ensure that all subjects have equal opportunity to participate

    38. Sensory difference exist when Certain notes are absent or of different intensity in aroma, taste, aftertaste the order of appearance of flavor notes differs total attribute intensity of flavor differs

    39. Principles of quantitative descriptive analysis: Variability is an inherent part of all response behaviors; all perceived characteristics of a product had to be accounted for; method is independent of specific subjects for all tests.

    40. Quantitative descriptive analysis Development of sensory language as a group panelist selection based on performance with test products 12-16 repeated judgments from each panelist individual evaluation booths unstructured scales ANOVA to evaluate individual and panel performance correlation coefficient to determine the relationship between various scales statistical analysis to determine primary sensory variables multidimensional model developed and related to consumer responses

    41. Definition of texture Texture is the sensory and functional manifestation of the structural and mechanical properties of foods detected through the senses of vision, touch, and kinesthetic

    42. Classification of textural characteristics Mechanical Hardness- soft, firm, hard Cohesiveness Brittleness-crumbly, crunchy, brittle Chewiness-tender, chewy, tough Gumminess-short, mealy, pasty, gummy Viscosity thin, thick Springiness - plastic, elastic Adhesiveness sticky, tacky, gooey

    43. Definitions Hardness forces required to compress a substance molar teeth or the tongue and palate. Cohesiveness amount of sample deformation before rupture when biting with molars Chewiness- number of chews required to masticate a sample at one chew per second and constant rate of force application to reduce it to a consistency suitable for swallowing. Gumminess- denseness that persits throughout mastication of a semisolid food. Viscosity force required to draw a liquid from a spoon over the tongue Springiness degree and speed with which material returns to its original height following partial compression with molars. Adhesiveness- force of the tongue required to remove the material that adheres to the mouth (palate), but also lips, teeth etc during normal eating process

    44. Classification of textural characterics Geometrical Particle size and shape gritty, grainy, coarse Particle shape and orientation fibrous, cellular, crystalline Moisture content dry, moist, wet, juicy Fat content Greasiness greasy Oiliness - oily

    45. Sequence of observations for particular product Surface partial compression first bite incisors first bite molars during chewing after swallowing

    46. SENSORY JUDGES Expert judges Trained judges (3-10) Semi-trained judges (8-25) Consumers (80+)

    47. Before selection of panelists we should know that: Sensory skills vary from person to person. Most individuals do not know what their ability is to taste and smell the product. All individuals should learn how to take a test. Not all individuals qualify for all tests Judges are rewarded for participation not for correct scores. Skills one acquired are forgotten if not used on a regular basis. Skills can be overworked or fatigued.

    48. Before selection of panelists we should know that: A judge performance can be influenced by numerous factors unrelated to the test or product. All judges information should be treated in a confidential manner. Judges should not be paid to participate in a sensory test. Test participation should be always on volunteer basis.

    49. Training judges: Use as test material the same products that will be tested. Prepare the test to obtain variations in product similar to those which will be met in the actual experiment. Adjust the difficulties of the test so the group as whole will discriminate between samples but some individuals will fail. Use test forms similar to those to be employed later. Start with a large group of candidates as feasible and a selection test that is operationally simple.

    50. Training judges: Screen on the basis of relative achievement continuing until a top ranking group of reliable size can be selected. At each step rejected those who are obviously inadequate, but retain more people than will be required for panel.

    51. Situation exercises You are employed as the sensory specialist by Dairy Best Ice Cream Company. The RD department is considering changing the flavouring ingredient for the strawberry yogurt to one of lower cost and has prepared samples for sensory evaluation. Discuss the situation and define the objective(s) of this study for sensory evaluation. Your company, a manufacturer of salad dressings has developed an additive-free line of salad dressings. As sensory specialist you are meeting with the quality assurance and marketing managers to discuss the use of sensory evaluation in the development of this product. Discuss this situation and define the objective of this study for sensory evaluation.