Descriptive analysis1 Dominique Valentin ENSBANA/CESG Université de Bourgogne...

Descriptive analysis 1

Descriptive analysisDominique Valentin

ENSBANA/CESGUniversité de [email protected]


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


When should we use descriptive analysis ?

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Packaging

R&D

Control quality

Marketing


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?


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


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?


Why should we use descriptive analysis ?

Contrary to informal product tasting, descriptive analysis limits:

Bias Subjectivity Poor control of variablesUsing wrong assessorsPatchy information


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 companyExternal: outside the company


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)


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


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 questionnairesAcuity testsRanking/rating testsPersonal interview


Example of prescreening questionnaire

Time:1) Are there any weekdays that you are not available on a regular basis2) 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?


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


Exemples de tests de sélection: jury bières

Matching odors / names

Descripteurs Composes Concentration (mg/L)

Banane Acétate d’isoamyle 5Amande amère Benzaldéhyde 2Citron Citral 2Vanille Vanilline 20Beurre 2,3-butanédione 5Rose Géraniol 5Eau Eau distillé – Chou Sulfure de diméthyle 0,05Fleur d’oranger Linalol 5

Chollet, 2000


Duo-trio test : • Control sample: Kronenbourg beer•Test sample: Heineken

Identification of 4 basic tastes

Descriptors Compound Concentration (g/l)

Sweet Sucrose 8Sour Citric Acid 1Bitter Caffein 0,5Astringent Aluminum Sulfate 0,5



Intensity ranking: sweet taste in beer

Sample Concentration (g/l)

1 02 53 104 15

Intensity ranking: Bitterness in beer

Beer Bitterness unit (EBU)

K 4Kronenbourg 151664 21Tradition allemande 28

Selection test example: beer panel


Odor descriptionComposés Descripteurs Concentration (mg/l)

Camphre Camphre 1Phényl acétaldéhyde jacinthe, lilas 5Acide octanoique Caprique 50Trans-2-hexenol Herbe coupée, feuille vertes 50Hexanoate d’éthyle Pomme, fruité, sucré, anisé 5-Décanolactone Pêche, abricot, noix de coco 202,5-diméthylepyrazine Céréales 20Isobutyraldéhyde Banane, amande 100Salycylate de méthyle Pharmacie, pommade 100Carvone Menthe, chlorphylle 100



Examples of scaling exercises

Mark on the line at the right to indicate the proportion of the area that is shaded

None All

None All

None AllMeilgaard, Civille & Carr (1999),Sensory evaluation techniques. CRC Press


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 8586-1:1993, Part 2: Experts, ISO 8586-2:1994



4-step process:

1. Panel selection


3. Training



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


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


Reduction of the list

1) Rearrange the list in family of terms (appearance, aroma, textures …)

2) Discuss with panelists to suppress:Hedonic and quantitative termsRedundant terms (synonyms)Non relevant terms


Example of lexicon

pomme fruitpomme cuitechimiquepoirecaramelfermentécoingvert-pas mûr

cidrevanillegraspomme vertepruneaupeau pommecitroncolle blanche

List of original terms

pomme fraîchecoingcidrepomme vertecaramelvanillepruneaupoiremétalliquegras

Final list

Not discriminantNot relevant

Synonyms


Examples of referents and definitions: Soy yogurts

Texture Thickness: consistency of the mass in the mouthRate of Melt: amount of product melted after a certain pressure of the tongueGraininess: amount of particle in massMouth coating: amount of film left on the mouth surfaces

Basic tastesSweet: SucroseSour: lactic acidBitter: caffeineSalty: sodium chloride

ArômeWater: taste like water down Flour: 1 spoon of flavor mixed in waterWood: cutting from pencil sharpening Chalk: smectaMilk: whole milk Raw pie crust: commercial raw pie crustCream: crème fraiche Hazelnut: : hazelnut powderEarthy: earth Mushroom: dry mushrooms soaked in water

TrigéminalAstringent: Shrininking or pukering of the tongue surface caused by tanins or alumn


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



4-step process:

1. Panel selection


3. Training



Training

Goal: assessors need to be able to detect and repeatedly quantify the sensory characteristicscorresponding 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


For each attribute:

1) Ranking testsPanelists 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


For each attribute:

2) Rating testsPanelists 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 sweetSweet

Very sweet


3) Final practice

Final practice should approach the testing situation in which the panel will be used:

Same type of productsSame experimental conditionsSeveral replicates

Panelists should receive feed back on their performance compare to that of the panel

Samples Average Panelist # 1

275 6.3 5.7391 5.7 4.2856 1.2 2.3912 3.6 3.7057 2.5 1.9

Samples Average Panelist # 2

275 6.3 2.3391 5.7 1.8856 1.2 4.6912 3.6 2.4057 2.5 3.5



4-step process:

1. Panel selection


3. Training



Pas du tout Très

Épais

Pas du tout Très

Gras

Pas du tout TrèsFondant

Code: 592

Pas du tout TrèsSucré

Pas du tout Très

Acide

Pas du tout Très

Amer

Pas du tout TrèsSalé

Pas du tout TrèsAstringent


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.


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


Many references exist to learn about sensory profilesThese include:

Sensory Evaluation Techniques, Third EditionMeilgaard, Morten C.Civille, Gail VanceCarr, B. ThomasCRC Press

Sensory Evaluation PracticesHerbert Stone, Joel L SidelAcademic Press

Sensory Evaluation of FoodPrinciples and PracticesHarry T. Lawless, Hildegarde HeymannAspen press

Descriptive analysis1 Dominique Valentin ENSBANA/CESG Université de Bourgogne...

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