ASTM DS72 Introduction
ASTM
 DS72 - LEXICON FOR SENSORY EVALUATION
 Aroma, Flavor, Texture, and Appearance

Introduction to The Lexicon

Introduction

THIS PUBLICATION is intended to assist descriptive-analysis panels and panel leaders in clarifying and refining the descriptive terms (vocabulary or lexicon) used to describe the aroma and/or flavor of finished products, ingredients, packaging, or chemicals used in the development, production, or storage of consumer products as well as tactile and visual attributes of an array of products ranging from foods, personal care products, and fabrics to household cleaners.

To use this resource effectively, researchers need to understand the rationale for the text by following the process described below for implementing a lexicon for the appearance, flavor/aroma and texture descriptions of a specific product category. THE PROCESS

Step 1: FRAME OF REFERENCE

If one's knowledge of flowers is based on a single rose bush, a description of all flowers' characteristics might be, “possessing a sweet aroma and thorns". With such a frame of reference, one's concept of the category is limiting.

In order to establish an appropriate frame of reference, a panel must become familiar with samples that span the product category.

Collect a large (6 to 12 samples) array of products or samples from the product or ingredient category to be evaluated. It is important to start with a broad representation of the flavor and texture characteristics expected in the products that will be evaluated by the descriptive analysis panel. This group of products or samples, which encompasses and defines the product category space, is called the product category frame of reference. For example, if the product category under investigation is "Italian salad dressing," the frame of reference is likely to include:
  • 4 to 8 commercially available Italian salad dressings from the products available in the geographic location/country for which the product is being studied.
  • 3 to 5 prototypes of the product that represent different ingredient and/or processing variables, such as sources of oil, vinegar, herbs, spices, onion, or garlic.

Step 2: TERM/LANGUAGE DEVELOPMENT/GENERATION

Prepare and present these samples to the entire panel for review. After the panelists have tasted the samples, have them list the flavor and textural characteristics of this category of products. Together with the panel, organize the terms from all of the lists into groups according to flavor or texture types/categories. Groupings or categories available from this lexicon include:
  • Chocolate/Nutty/Woody/Coffee/Tea (chocolate, cocoa, peanut, almond).
  • Dairy (milky, buttery, cheesy).
  • Edible Oil (corn, soy, cottonseed).
  • Fermented Grain and Fruit Products (spirits, wine, beer).
  • Fish/Shellfish (bluefish, cod, mackerel, crab).
  • Fruit - Berries, Citrus, Pome, Stone, Tropical (strawberry, apple, pear, peach, lemon, lime, orange).
  • Grain (whole wheat, white wheat, rye, oat, corn).
  • Meat/Poultry - Cured, processed, Uncured fabricated, processed, ready to cook (beef, pork, chicken, turkey).
  • Other (rubber-mercaptan, petroleum, plastic).
  • Spices - Green Herbs, Peppers, Roots, Seeds, Sweet (clove, cinnamon, nutmeg, cardamom, thyme, basil, weedy, dill, parsley).
  • Sweet Aromatics (caramelized, maple, honey).
  • Vegetable (tomato, celery, potato, carrot).
  • Surface: loose particles, oiliness.
  • First bite: hardness, denseness, cohesiveness.
  • Mastication: moistness of mass, awareness of chips.
  • Residual: oily mouthcoat.
For the Italian salad dressing example, attributes might fall into the categories of Edible Oils, Spices - Green Herbs, Vegetable, and Spices - Sweet.

This Aroma/Flavor Lexicon is divided into four sections for easy use:
  • List of the categories of products with specific products that are included in each category. For example, Dairy (category)—butter, cheese, general dairy, and yogurt (the products covered within Dairy). The page number for finding the specific terms attached to the category-product combination follows.
  • List of the category with products with terms that describe that product. For example, Dairy (category), Yogurt (product)—acid/sour, bitter, cooked/heated, green/course, rancid, sour, sour/acid, stabilized flavor (terms).
  • Dictionary includes all terms in alphabetical order with a definition, one or more references, the preparation protocol for the references, and some examples of products that clearly demonstrate the term.
  • Index is the alphabetical ordering of all terms with cross-referenced page numbers for finding the products that use the term in their descriptions and for finding the details of the term in the dictionary section.

Step 3: USE OF REFERENCES

Now it is time to use the lexicon. From each grouping, choose one or more references for each term, prepare according to the instructions, and present to panel. A reference is a substance (a chemical or a simple substance) that provides a clear and distinct demonstration of the term or characteristic in question; it is important that the characteristic be the predominant trait in the reference. The object is to clarify panelist's perception of the characteristic and identify the appropriate term using each reference. Panelists are encouraged to discuss their individual descriptions of each reference to allow the group to reach a consensus definition of each term. For example, to experience the individual flavor types and perceive flavor similarities that exist among the sweet aromatic references in terms of caramelized character, present a reference that demonstrates each of the characteristics—caramelized, honey, molasses, and brown sugar. This enables the panelists to experience and contrast the differences among these references. The floral of the honey, the sulfur of the molasses, and the smoky and/or woody in the maple are characteristic of the specific sweet aromatics and enable the panelists to identify the appropriate word to describe each distinct flavor, while experiencing the common caramelized character.

Step 4: USE OF EXAMPLES

To help clarify each term generated in Step 2, the panel leader is encouraged to present one or more examples from the lexicon. An example is a product or substance in which the term or characteristic can be readily perceived, although not as singularly as in a reference, enabling the panelists to experience the flavor/texture character and its corresponding term in a product. The examples tend to demonstrate the characteristic in the presence of one or more other characteristics. The use of difference examples provides a concept space to the panelists from which they can understand the attribute associated with the term in question. For "caramelized" sweetened condensed milk, toffee or ale serve as good examples.

Step 5: DEVELOPING THE LIST OF DESCRIPTORS

Once the panelists agree to use the terms they derive after using the lexicon references and examples, the panel leader can present the category frame of reference again with the list of terms from the first evaluation. The panelists are encouraged to refine the list of terms so that it is comprehensive enough to describe all relevant flavor notes/texture characteristics without being redundant. For example, when evaluating a cinnamon flavored confection, it is not necessary to list cinnamon, cinnamic aldehyde, cassia, woody, and sweet brown spice as descriptors for a product with powdered cinnamon added. In this case, only cinnamon and woody are sufficient for a comprehensive description. The selection of terms is dependent upon the panel's review of the frame of reference, the quality of the relevant references and examples, and the ability of the panelists to use these resources, and through discussion, arrive at the best product lexicon. These terms are provided as guidelines to a panel and may be refined by the panel to reflect the panel's understanding of a term or set of terms.

CONCLUSION

Panelists and panel leaders are discouraged from reading a product's ingredients list to determine the product's descriptive terms. The presence of an ingredient in a formula or ingredient list does not assure that its characteristic(s) are perceivable. The corollary to this is true, as well. The perception of a particular property or flavor characteristic, minty or garlic or rose, does not necessarily mean that the corresponding substance, peppermint or garlic or rose oil, is present in the sample. Although this lexicon is quite extensive, it certainly does not contain all or even most of the possible flavor descriptive terms that a panel might generate. As the panel works together with its panel leader to uncover and discover the best lexicon for a particular product category, they may encounter new terms with corresponding references and examples. In such cases the terms, references, and examples can be added to the lexicon. It is likely that each company and institution may already have developed additional words for the products of interest. Panel leaders and product developers should not expect these terms to be the same as the terminology used by consumers in consumer com-plaints or consumer research testing.

CAUTION: Care must be taken in the use of all references with panelists. Care must be used in determining if certain substances are safe for sniffing only or ingesting. Panel leaders should refer to the following reference texts before introducing any chemical substance to the panel:
  • Material Safety Data Sheets - These provide information on proper methods of handling, storing, and disposing of chemicals, as well as TLV (threshold limit value) for exposure concentrations.
  • American Conference of Governmental Industrial Hygienists, "1991-92 Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices," ACGIH, 1991.
  • Clayton, George, D. and Clayton, Florence, E. Patty's Industrial Hygiene and Toxicology, Fourth Edition, Volume IA - Toxicology, John Wiley & Sons, New York, 1991.
  • Proctor, N. H., Hughes, J. P., and Fischman, M. L. Chemical Hazards of the Workplace, Second Edition, Von Nostrand Reinhold, New York, 1989.
  • Sax, Irving, Dangerous Properties of Industrial Materials, Fourth Edition, Von Reinhold, New York, 1975.




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