Study of he sensory mechanisms and cognitive processes that are the basis for sensory evaluation and consumer testing. Taste psychophysics, Thurstonian models, signal detection, concept formation and measurement, discrimination methods, scaling, cross-cultural studies, statistics.
RECENT SIGNIFICANT FINDINGS
It is often important to determine whether very slight differences in food flavor actually exist or not. For this, there are a whole set of tests called difference tests. These vary in their sensitivity; a given judge will discriminate between two foods using one test protocol but not discriminate using another. Even a slight change in the wording of instructions to a judge will affect the search procedure set up in his head and completely alter his performance. This has not been well understood. This lab developed a model based on physiological and brain processing effects to explain such variations. The lab also challenged the conventional theories in this area and demonstrated how they were based on faulty assumptions. A new model combining the best parts of the various rival theoretical approaches has been developed and explains most of the variation in test sensitivity. This can now be used to vary the sensitivity of judges as required for the various types of sensory measurement encountered in the food industry and academic research.
Sensory difference tests have always been 'all or none' affairs, giving results in terms of 'the foods are different' vs 'not different'. However, an application of Signal Detection Theory, an approach involving the analysis of the nervous system as a communications system, can provide more sophisticated information. Instead of 'different' vs 'not different', a measure of 'how different' is now available. There are several measures of degree of difference but this lab has developed the R-index, a simple yet robust measure based on minimal statistical assumptions. Because of this, it has wide applicability.
Descriptive analysis provides a description of all the various sensations a food gives to the taster and their relative strengths. It is a widely used technique providing 'profiles' of various food products, that can be compared and used to assess characteristics of products which are important for consumer acceptance. However, it is difficult to describe tastes or smells because we have not developed sufficient language to do so. Thus, a language and categorization system has to be developed for each food and judges must be trained to use it. This lab has studied the information processing that takes place in the brain for such a system to be developed. We have developed a theoretical basis and successfully used it to develop techniques to increase the performance and speed up training of judges using this method.
Descriptive analysis requires a lot of training and expense. Some systems need approx. 100 hours to train and calibrate judges before they can be used. This lab has developed an alternative technique called Focused Difference Testing, which requires little training and relies on the natural biases and skills, as well as robust alternative methodology developed in the lab to produce profiles.
It was long suspected that fluctuations in salivary content affected taste sensitivity. This is important because tests that measure taste sensitivity are being used more and more in the diagnosis of various disfunctions like cystic fibrosis, hypertension, adrenal cortical changes (Addison's disease, Cushing's syndrome) etc. Although the connection between taste and saliva was suspected, it could not be demonstrated. One reason for this is that as soon as a judge tasted a test stimulus, the environment in the mouth was changed so destroying any effects of saliva. However, a direct connection between saliva and taste sensitivity was established in this lab, using specialized sensory measurement techniques developed by this lab.
As a judge undergoes repeated testing, his taste sensitivity is reduced; this is a perfectly normal sensory function and is called adaptation. Adaptation has been studied extensively in this lab and techniques developed so that sensitivity is not lost during testing.
A common misconception is that there are four basic tastes: 'sweet', 'sour', 'salty' and 'bitter'. The idea was based on mistaken translation from early German research and, unfortunately, has become established in most textbooks. Methods of measurement based on this fallacious idea have produced many artifactual results. Work in this lab has demonstrated the artifactual nature of these measures, often in the teeth of angry opposition.
