Relationship between instrumental texture measurements and sensory attributes

The ultimate physical property of foodstuffs is the sensory attribute of texture as encountered in the mouth. This property can determine whether it is acceptable or otherwise to the consumer. In some culinary cultures, the Japanese in particular, the texture is a primary attribute. To quantify this property is difficult as the flow behaviour in the mouth is very complex. The shear rates or deformations encountered is three dimensional and not constant. Therefore, instrumentation has attempted to simulate mastication rather than a holistic behaviour in the mouth. This has lead to empirical relationships that are very narrow in scope, and attempt to address several characteristics simultaneously. Each foodstuff has its own set of correlations and their relationship cannot be cross correlated. Worse still, even within a particular type of food, hard yellow cheeses for example, the correlation of some of the textural properties are good while others fail. An example of the hardness, cohesiveness, adhesiveness of full fat yellow cheeses will be discussed. On the liquid side, the relationship is still being defined. Viscosity in all its complexities exist in food stuffs. Correlation of the flow of materials over the tongue and its textural mouth feel is very difficult to define, and attempt to correlate with rheological model parameters has not yet been successful. This is within the realms where rheological models can be often correlated with components such as fat concentrations. However, it is the mouth feel that is of importance to consumers, and with the health conscious modern world, fat substitutes to mimic mouth feel will become highly sought, but instrumentation to provide a means of measuring the characteristics will be needed for design and quality control of the product. The sensory attributes of milks as a function of fat content will be used to illustrate this point. The conclusion that can be made is that the behaviour of the foodstuffs in the mouth is not yet understood, nor is the method by which the mouth senses the different textures. Therefore attempts to simulate and quantify the sensations with instruments is unrealised as yet and therefore, the empirical approach must dominate at this stage. However, work should continue to understand the fundamentals of processes in the mouth, food behaviour under those circumstances and the stimuli created. Only then will we really be able to use instruments to predict sensory evaluation of the consumer.