Introducing temporal dominance of sensation

In product research and development in the food industry, it is important to understand the key sensory attributes of a product (aroma, flavour and mouth feel) to guide its development or modification. This may be useful when food companies wish to modify ingredients to develop a healthier product, to alter or eliminate undesirable characteristics, to add or enhance a particular characteristic, or in the initial development of a novel product.

A traditional method used to describe a products sensory attributes is Quantitative Descriptive Analysis (QDA). This method identifies all sensory attributes to describe a given product as well as providing an intensity rating for each attribute identified. Traditionally, a group of expert assessors form a panel and are trained to be able to accurately and repeatedly describe the characteristics present and quantify the intensity of each of the attributes on a line scale. The descriptive language used is devised and defined by the panel members with the guidance of a panel leader so all panel members understand and use the descriptors in the same way.

An example of a product being evaluated using QDA is chocolate. Some of the attributes that may be used to describe the flavour of chocolate are sweet, bitter and nutty. These would be evaluated on line scales like the ones below.

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For some products, such as the freshness of chewing gum, it may be important to include information on both the intensity and duration of each attribute. The intensity is evaluated at various time points to produce a curve of the intensity and duration. However only one or two attributes can be evaluated at a time. The figure below provides an example of an evaluation of chewing gum using the time-intensity method.

ImageTo be able to evaluate more than one attribute at a time using intensity and duration, a method was developed by Pascal Schlich and his research group in 2003 termed Temporal Dominance of Sensation (TDS). This method looks at a single eating event and identifies the dominant sensory attribute at any given point in time during the eating process. TDS is a technique whereby the intensity of dominant attributes are evaluated at the time sensations begin, repeatedly until the sensations end. Upon swallowing the product of interest a trained assessor will select the dominant attribute and rate the intensity of that attribute until the dominant attribute changes. The assessor will continue to evaluate the intensity of the dominant attribute until all sensations end. This method may be useful when the product of interest has a lingering after taste or effect, such as with chewing gum or mint flavoured confectionary.

During an evaluation, all attributes will appear simultaneously on a screen for the duration of the analysis. Upon commencing the evaluation, the time that each attribute is selected as dominant will be recorded together with the concurrent recorded intensity. The below figures provide an example of what the screen would look like for assessors evaluating a mint flavoured candy if minty was selected as the first dominant attribute.

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When collating the results obtained via the TDS method a temporal dominance of sensation curve may be established. The below figure illustrates the dominant attributes pertaining to a mint flavoured candy using the TDS method.

ImageThis methodology may be a welcomed addition to quantitative descriptive analysis to provide a more comprehensive picture of the sensations occurring during and following an eating event to assist food companies in product research and development.

References:

Cliff, M., & Heymann, H. (1993). Development and use of time-intensity methodology for sensory evaluation – a review. Food Research International, 26, 375–385.

Labbe, D., Schlich, P., Pineau, N., Gilbert, F., & Martin, N. (2009). Temporal Dominance of Sensations and sensory profiling: A comparative study. Food Quality and Preference, 20, 216–221.

Larson-Powers, M., & Pangborn, R. M. (1978). Paired comparison and time-intensity measurements of the sensory properties of beverages and gelatins containing sucrose or synthetic sweeteners. Journal of Food Science, 43, 41–46.

Pineau, N., Schlich, P., Issanchou, S., Imbert, A., Cordelle, S., Mathonnière, C., et al. (2009). Temporal Dominance of Sensations: Construction of the TDS curves and comparison with time-intensity. Food Quality and Preference, 20, 450–455.

Stone, H., Sidel, J. L., Oliver, S., Woolsey, A., & Singleton, R. C. (1974). Sensory evaluation by quantitative descriptive analysis. Food Technology, 28, 24–33.

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About Centre for Advanced Sensory Science (CASS)

The Deakin University Centre for Advanced Sensory Science (CASS) in Melbourne is dedicated to helping the sustainable growth of the Australian food industry by being a provider of high quality sensory and flavour research, and training the next generation of sensory scientists.
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