Objectives: 1. Describe the applications of descriptive analysis. Examine the language and scaling components of descriptive analysis. Follow the descriptive analysis process from terminology development to data analysis and reporting. Explore ways to monitor judge performance. Review statistical methods of descriptive data analysis. We use descriptive analysis methods to obtain detailed descriptions of the appearance, aroma, flavor, and oral texture of foods and beverages, the skin-feel of personal care products, the hand-feel of fabrics and paper products, and more generally, the sensory properties of any product.
Some professionals extend further this broad definition to the quantitative evaluation of the 'attributes' of any product or service, but we will stick to sensory attributes in this lesson. These pictures show a judge conducting a descriptive analysis of a skincare cream, and another evaluating a makeup sample. For these types of products, the evaluation protocol is very important because it can clearly affect how consumers perceive the product.
The figure below shows how selected sensory attributes in beer vary as a function of storage time. This is particularly relevant for the assessment of color, texture, and flavor in foods and beverages. For example, the real degree of fermentation RDF and dissolved carbon dioxide are predictors of foam volume as perceived in the mouth. The instrument records the amount of force required to deform the sample and the resulting profile of force vs. We can see that the instrument can adequately predict textural differences among gels made with gelatin, alginate or carrageenan.
We can attempt to correlate peak height or area with flavor notes perceived by a descriptive panel. Quantify a product's sensory attributes to use in external preference mapping Course 3. Little, as described by Cairncross and Sjostrom in These investigators showed that it was possible to select and train individuals to describe their perception of a product in some agreed sequence, leading to actionable results in this way avoid the need for an 'expert'.
Stone, J. Sidel and collaborators in Even though the first flavor wheel was developed by the British whisky industry to describe whisky flavors, the first widely- publicized flavor wheel was the Beer Flavor Wheel shown here.
Influential members of the Department of Viticulture and Enology at UC Davis including Maynard Amerine - top, right are shown tasting wine in the s. The other photo shows the time- intensity profiles of different concentrations of iso-alpha-acids - the bitter principle in beer. The Spectrum Method, with its deliberate guidance of the panel, intensive training, absolute ratings and extensive use of references and calibration points represented a degree philosophical shift from the QDA.
Term generation 2. Development of definitions and references for the attributes 3. Scorecard development sequence of attributes, evaluation protocols, and scale 4. Training group and individual 5. Assessment of judge performance and readiness 6. Descriptive analysis 7.
We displayed the beer flavor wheel and the wine aroma wheel in the history segment of this lesson. We organize the terms by level of specificity, from the sensory modality stimulated e. The panel chooses terms that best describe the differences among the products, with the right level of specificity. In some cases, fruity may be adequate. But in others, more specific descriptors of the type of fruitiness may be indicated e.
The panel may also choose to combine descriptors to cover a broader range of attributes in the products e. It is critical that all judges on the panel understand the descriptive terms in the same way concept alignment. Let's use the color RED as an example of a sensory attribute we want to explain to an individual who has no concept of what the color RED is. The brain may formulate this new concept by looking at one example of the color RED and generalizing from it.
The tracing of boundaries around that example is arbitrary, though. This step is called generalization. If we also present colors that are part of the RED concept and colors that are not, the brain can pinpoint the RED concept further by abstraction sometimes called discrimination in other disciplines.
The best way we achieve concept alignment the same understanding of a sensory concept by all the judges on the panel is through this two-step process of abstraction and generalization.
Someone who is very familiar with the world of colors will understand the RED concept much easier and faster than someone who has never seen colors before. Some sensory concepts are more discrete than others. By this we mean that the line between two attributes e. See Reading Assignment 7. But it is a risky practice at best. Product variations resulting from ingredients or processing changes rarely affect just one attribute, thus attesting to the complexity of the descriptive process.
Language itself evolves. Different terms may have different meanings to different individuals. This is particularly relevant when it comes to 'technical' terms. But allowing the panel to develop the terminology to be used in the final descriptive analysis should never be at the expense of rigorous analytical work, and the requirements for 'good' descriptors listed above always apply and should be considered carefully. Other methods require that judges use the scale exactly in the same way calibration and extensive training is required so that judges assign approximately the same score to a given sample.
The latter can be done and may be needed for some applications , but it obviously requires a lot of training. This is a somewhat controversial issue because these parameters do not meet the requirements we set for the descriptors noted above. Except for the first two e. Yet, consumers usually expect some measure of complexity, balance or quality by 'experts' to be available.
Many of us buy wine at the supermarket or liquor store based on the ratings they received on a point scale from well-known wine publications. We should agree though that hedonic ratings e.
Because the judges on a descriptive analysis panel are not representing the consumer population, their hedonic ratings can mislead product developers or quality assurance specialists. Hedonic ratings should be obtained from consumers, not trained judges. The following article describes a study of Lager beers, in which we had trained experts conduct a descriptive analysis of the sensory properties of the beers, as well as provide quality ratings.
So beware that quality ratings are a challenging exercise. For most consumer products, though, we feel quality ratings should be developed to guide consumers in their purchases.
Consumers Union, the publishers of the Consumer Reports magazine, have had a longstanding tradition of excellence in the development of quality ratings that usually include sensory criteria.
They have been successful at having experts provide accurate, reliable, and consistent evaluation of all kinds of consumer products, from running shoes to wine to handheld PDAs. The purpose of screening potential judges should be to ensure that they can perceive differences at better than chance level among products of the kind that is to be evaluated by descriptive analysis.
Furthermore, the experimenter should ensure that motivation, sound intellect, and availability complete the potential judge's profile. Sensory Acuity Performance in sensory tests with simple stimuli basic tastes, smells does not adequately predict performance with actual products; therefore, such tests are generally a waste of the investigator's time and resources.
Instead, judges should be screened with actual products. Difference tests with samples that are significantly, but barely, different are ideal. In the QDA method, for example, 20 to 30 discrimination trials fielded over 2 or 3 days are recommended to select judges from a pool of individuals naive to sensory testing. Scaling exercises may also be useful on what is believed to be key sensory attributes and representative samples for the product under study.
Keep in mind that screening is intended primarily to eliminate non-discriminators and secondarily to familiarize the judges with the sensory properties of the product. It does not eliminate the need for training the panel. Note that most descriptive analysis methods do not call for screening potential judges for sensory acuity. But it just makes sense… so to speak. Intellect A comment about the type of individual to look for in descriptive analysis: in addition to having good sensory abilities, ideal judges are those with good intellectual abilities.
This is because descriptive analysis is a sensory as well as an intellectual exercise that requires a great deal of analytical skill and concentration. Motivation and Availability In the end, motivation and availability might be the most important features to look for in your selection of judges. As always, best practices in sensory evaluation begin with good common sense. Maintaining panel motivation throughout the descriptive analysis process by providing feedback to the judges is also critical.
Some methods deliver the list of attributes to the judges, along with corresponding definitions, evaluation protocols and multiple references, and the early stages of the descriptive analysis are spent training the panel on those.
Other methods rely entirely on the panel for term generation, definitions, evaluation protocols, and may or may not advocate the use of references.
Again common sense should prevail here, and we will argue that the road to travel may be somewhere between those two extremes. Term Generation Unless the method stipulates that the experimenters pre- select the attributes to be evaluated and merely teach the panel how to rate them, it is up to the panel to come up with a sensory lexicon describing the sensory attributes of the product.
This is typically done by showing the panel a set of samples representative in terms of both range and intensities of attributes of the samples to be tested in the actual descriptive analysis over several sessions. With each sample, judges are encouraged to propose terms describing the sensory attributes, usually with a focus on those attributes that tend to differ among samples.
Both photos show descriptive panels at work during the term generation phase. In some cases, the attribute may be straightforward e. But in most cases, the attribute may be interpreted in a number of ways, and this is why it is important to define it as precisely as possible. For example, if a panel chooses to include the term 'strawberry aroma' in the scorecard, the panel must define what type of strawberry aroma it is referring to: for example, is it fresh strawberry, overripe strawberry, or strawberry jam?
Otherwise, the risk of poor concept alignment may be significant. Evaluation Protocols The same logic applies to the careful development of evaluation protocols. To ensure that everyone on the panel is working as one instrument, it is important that all judges evaluate each attribute in the same way. For example, an evaluation of chewiness should specify how to chew the sample e.
How many chews? We believe that they are particularly indicated for appearance and flavor attributes color, aroma, taste, chemical irritation because they can readily be developed for those modalities. For other types of attributes, such as texture and mouth-feel, it may be more challenging to develop a reference to illustrate an attribute.
The table to the left shows a list of terms used in the descriptive analysis of Pinot noir wines and the recipes for making the corresponding references. The photo shows members of a descriptive panel sniffing wine aroma references. Those were made by spiking a neutral base wine with specific items that illustrate the flavors in the scorecard for example, some freshly cut grass soaked in base wine as a reference for 'grassy' flavor, or a few drops of vanilla extract in base wine to represent 'vanilla' flavor, etc.
Judges are asked to carefully evaluate each reference for accuracy does it really pinpoint the flavor of interest? This way, the experimenter may achieve concept alignment across the panel.
Returning to our discussion of concept formation above, we can extend the principles of concept formation to the use of references in descriptive analysis. In most cases, we resort to generalization to teach a sensory concept to the judge.
This means that we make a reference that illustrates the flavor note of interest and the judge must generalize that concept from the reference. For example, we might take a neutral sample and spike it with an item or a chemical to impart the flavor note of interest.
In other instances, however, we may not be able to manufacture a sample that illustrates the attribute for most texture attributes, for example , and we typically resort to abstraction to illustrate a concept. We show the panel samples with the attribute and samples without it, and hope that the judge can understand the concept by abstraction See Reading Assignment 6. They may be graphic, line scales or numerical scales. They are typically anchored with terms such as "low" and "high," or "none" and "extreme," and may include additional terms along the scale.
Our recommendations are: 1. Make sure that the scale has enough categories to adequately discriminate among the samples. As shown in our scaling lesson, many features on a scale are not useful and may actually confuse the judge. Even more important than the design of the scale is to know how the judges will use it.
Depending on the descriptive method, the expectations of the panel will range from relative to absolute ratings, the latter requiring extensive calibration with multiple references. Need an account? Click here to sign up. Download Free PDF.
Oladoye Segun. A short summary of this paper. Download Download PDF. Translate PDF. Therefore, knowing consumers' preferences and perceptions of the sensory characteristics of food products is very important to food manufacturers and retailers alike. The discipline does not just deal with "likes and dislikes," but scientifically evokes, measures, analyses and interprets psychological responses to physical stimuli, and thus belongs to the specialized field of psychophysics.
In a taste panel, these senses can be measured scientifically to obtain information about particular aspects of a food.
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