MECHANISMS INVOLVED IN the INFUSION of STARCH BASED POROUS FOOD MATERIALS BY OIL BASED LIQUID FOODS.

Mechanisms involved in "infusion", defined as filling in the pores of starch based solid foods with high calorie liquid foods to obtain calorically dense food products, were investigated. Parameters under investigation were the effect of: Pore structure of the solid matrix on infusion uniformity, wettability of the solid matrix on the rate of liquid uptake, viscosity (apparent viscosity for non-Newtonian liquids) and surface tension of the infusing liquid on the rate of liquid uptake and the pressure gradient to be imposed. Infusion uniformity could not be achieved with chocolate syrup, no matter whether the porous solid matrix was highly expanded (Bread, porosity = 0.9) or relatively compact (Cookies, porosity = 0.6), due to the filtration of particulate solids. Infusion was found to be a fast, efficient process which takes place between a moderate vacuum and barometric pressure. For Newtonian oils, wettability was found to be the major mechanism of infusion.