In vitro simulation of the oral processing of semi-solid foods

The intra-oral processing of semi-solids foods is dominated by effects due to tongue movement. These movements subject the food to shear forces and mix it with saliva. Both actions tend to reduce the viscosity of the products. These changes are perceived as ¿melting¿ by sensory panellists. In a previous study where subjects were trained to use a variety of intra-oral manipulation it was shown that the amount of tongue movement was an important factor in determining the sensory experience of the products. The goal of this study was to develop a system which could measure changes in viscosity due to temperature, shear, dilution and structure breakdown, monitor the rate of and extent of mixing, mimic the pattern of mixing extant in the mouth. Simulation requires that shear forces, mixing and thermal effects be mimicked faithfully. To compare samples recovered from the mouth with those mixed in the simulator we compare the amount of mixing as measured using an image-processing technique. The simulator allows the effects of shear, dilution, and ¿-amylase concentration on the rheology and heterogeneity of the product to be monitored in real time. By way of example the effects of dilution, shear and chemical breakdown are compared in a starch-based semi-solid food.