Presentation on theme: "Descriptive analysis1 Dominique Valentin ENSBANA/CESG Université de Bourgogne"— Presentation transcript:
Descriptive analysis1 Dominique Valentin ENSBANA/CESG Université de Bourgogne
Descriptive analysis2 What is descriptive analysis ? Descriptive analysis is used to describe the sensory characteristics of a product, and to use these characteristics to quantify differences between products Sensory profile radar
Descriptive analysis3 When should we use descriptive analysis ? Descriptive analysis Packaging R&D Control quality Marketing
Descriptive analysis4 Quality control Does this product match the target specification? What variation in quality is to be expected? What is the normal variation in each attributes How long can this product be stored before the Sensory quality noticeably changes?
Descriptive analysis5 Research & Development What are my product perceived sensory characteristics ? How can it be made more like the target profile? Have the changes brought the product closer to the target? If the recipe/process were changed, how would quality be affected
Descriptive analysis6 Marketing and Packaging What are the attributes of products already on the market? What are the attributes of the most and least succesfull products? What are the key attributes to meet consumers’ Expectations? Have the changes brought the product closer to the target?
Descriptive analysis7 Why should we use descriptive analysis ? Contrary to informal product tasting, descriptive analysis limits: Bias Subjectivity Poor control of variables Using wrong assessors Patchy information
Descriptive analysis8 What sort of panel is required ? Trained panel: more capable of describing the subtle differences between samples 2 types of trained panels: Internal: within the company External: outside the company
Descriptive analysis9 What type of methods should we use ? Conventional Profiling (QDA ® Stone et al, 1974) Marketed by the Tragon Corporation in the USA Free Choice profiling (Williams and Langron, 1984) Profil Flash (Siefferman, 2000)
Descriptive analysis10 Conventional Profiling 4-step process: 1.Panel selection 2.Development of a lexicon for appearance, odor, flavor, texture, mouth feel and after- taste 3.Training 4.Ratings of the products
Descriptive analysis11 Panel selection Ability to detect differences in characteristics present and in their intensities Ability to describe characteristics using verbal descriptors and scaling methods Capacity for abstract reasoning Interest in participation and availability General good health Prescreening questionnaires Acuity tests Ranking/rating tests Personal interview
Descriptive analysis12 Example of prescreening questionnaire Time: 1)Are there any weekdays that you are not available on a regular basis 2)How many weeks of vacation do you plan to take this year Health: 1)Do you have any of the following Dentures Diabetes Oral or gum disease Hypoglycemia Food allergies Hypertension 2) Do you take any medications which affect your senses, especially taste and smell?
Descriptive analysis13 Flavor, fragrance and texture quiz: 1)If a recipe calls for thyme and there is none available, what would you substitute? 2)What are some other food that taste like yogurt? 3)What is the best one- or two-word description of grated Italian cheese 4)Describe some noticeable flavors in cola 5)Describe some of the textural properties of foods in general 6)What are some textural properties of potato chips 7)Describe some of the noticeable smells in a bakery Meilgaard, Civille & Carr (1999), Sensory evaluation techniques. CRC Press
Descriptive analysis18 Examples of scaling exercises Mark on the line at the right to indicate the proportion of the area that is shaded NoneAll NoneAll NoneAll Meilgaard, Civille & Carr (1999), Sensory evaluation techniques. CRC Press
Descriptive analysis19 If you want to know more: Guidelines for the selection and training of sensory panel members ASTM special technical publication 758 Sensory analysis -- General guidance for the selection, training and monitoring of assessors -- Part 1: Selected assessors, ISO :1993, Part 2: Experts, ISO :1994
Descriptive analysis20 Conventional Profiling 4-step process: 1.Panel selection 2.Development of a lexicon for appearance, odor, flavor, texture, mouth feel and after- taste 3.Training 4.Ratings of the products
Descriptive analysis21 Development of a lexicon Goal: Describe the product category completely without overlapping Procedure: Word generation Reduction of the list into a working list Choice of referents and definitions for the descriptors
Descriptive analysis22 1.Collect commercially available samples which represents as many as possible of the attribute differences likely to be encountered in the product category 2.Present 4 samples to the panelists and ask them to write down independantly as many terms as they can to describe the sensory characteristics fully 3.Compile the terms given by all the panelists to form a list of descritors Word generation
Descriptive analysis23 Reduction of the list 1)Rearrange the list in family of terms (appearance, aroma, textures …) 2) Discuss with panelists to suppress: Hedonic and quantitative terms Redundant terms (synonyms) Non relevant terms
Descriptive analysis24 Example of lexicon pomme fruit pomme cuite chimique poire caramel fermenté coing vert-pas mûr cidre vanille gras pomme verte pruneau peau pomme citron colle blanche List of original terms pomme fraîche coing cidre pomme verte caramel vanille pruneau poire métallique gras Final list Not discriminant Not relevant Synonyms
Descriptive analysis25 Examples of referents and definitions: Soy yogurts Texture Thickness: consistency of the mass in the mouth Rate of Melt: amount of product melted after a certain pressure of the tongue Graininess: amount of particle in mass Mouth coating: amount of film left on the mouth surfaces Basic tastes Sweet: Sucrose Sour: lactic acid Bitter: caffeine Salty: sodium chloride Arôme Water: taste like water downFlour: 1 spoon of flavor mixed in water Wood: cutting from pencil sharpeningChalk: smecta Milk: whole milkRaw pie crust: commercial raw pie crust Cream: crème fraicheHazelnut: : hazelnut powder Earthy: earthMushroom: dry mushrooms soaked in water Trigéminal Astringent: Shrininking or pukering of the tongue surface caused by tanins or alumn
Descriptive analysis26 Procedure for manipulation of the samples 1)First compression (e.g. thickness) Place ½ spoon of sample in mouth and compress between tongue and palate 2)Manipulation (e.g. rate of melt, graininess) Compress sample several more times (2 to 3 times) 3)After feel (e.g. mouth coating) Swallow or expectorate
Descriptive analysis27 Conventional Profiling 4-step process: 1.Panel selection 2.Development of a lexicon for appearance, odor, flavor, texture, mouth feel and after- taste 3.Training 4.Ratings of the products
Descriptive analysis28 Training Goal: assessors need to be able to detect and repeatedly quantify the sensory characteristics corresponding to the lexicon Need to be exposed to a wide range of products Need to be familiarized with the use of the scale Need to receive feed back to rectify any problem
Descriptive analysis29 For each attribute: 1)Ranking tests Panelists receive 4 samples covering the range of differences likely to be encountered in the product category and are asked to rank them according to the attribute Sweetness
Descriptive analysis30 For each attribute: 2) Rating tests Panelists receive 4 sample and are asked to score them on an intensity scale Start with large differences, then collect samples which represent smaller differences within the product category Encourage panelists to refine the procedures for evaluation and terminology with definitions and references Not sweet Sweet Very sweet
Descriptive analysis31 3) Final practice Final practice should approach the testing situation in which the panel will be used: Same type of products Same experimental conditions Several replicates Panelists should receive feed back on their performance compare to that of the panel SamplesAveragePanelist # SamplesAveragePanelist #
Descriptive analysis32 Conventional Profiling 4-step process: 1.Panel selection 2.Development of a lexicon for appearance, odor, flavor, texture, mouth feel and after- taste 3.Training 4.Ratings of the products
Descriptive analysis33 Pas du tout Très Épais Pas du tout Très Gras Pas du tout Très Fondant Code: 592 Pas du tout Très Sucré Pas du tout Très Acide Pas du tout Très Amer Pas du tout Très Salé Pas du tout Très Astringent
Descriptive analysis34 FAQs How many assessors do we need ? How many samples are there ? How many replicates are necessary ? Normally 3 assessments per sample/assessors, however this is very expensive in time and resource. If the panel is fully trained and constantly evaluating the same type of products then a single assessment is likely to provide reliable data otherwise 1 or 2 replicates are advisable.
Descriptive analysis35 How many training sessions? The number of training sessions depends on the complexity of the product, on the number of attributes to be covered, on the requirement for validity and reliability A more experienced panel will provide greater detail with greater reproducibility but a short version with fewer and simpler attributes is acceptable for control quality for example
Descriptive analysis36 Many references exist to learn about sensory profiles These include: Sensory Evaluation Techniques, Third Edition Meilgaard, Morten C. Civille, Gail Vance Carr, B. Thomas CRC Press Sensory Evaluation Practices Herbert Stone, Joel L Sidel Academic Press Sensory Evaluation of Food Principles and Practices Harry T. Lawless, Hildegarde Heymann Aspen press