Helsinki: University of Helsinki, 2002. – 86 p.During microwave frequency heating many variables in the food, package, and the microwave oven itself affect how the food is heated. Multicomponent foods in particular heat unevenly, causing problems with both sensory and microbiological quality. It is difficult to quantify the influence of factors
affecting microwave heating uniformity of foods. This is due, at least partly, to the problems in measuring temperature distribution and the interaction between oven and the food. The objective of this study was to improve the quality of microwave heated multicomponent foods by better understanding of the factors controlling heating uniformity and the consumer perception thereof.
Dielectric properties of some food ingredients and components were measured by a cavity perturbation technique at temperatures up to 95ºC. Food material used in the heating experiments were chilled ready meals and hamburgers. Temperature was measured by a fibre optic system during microwave heating and by thermocouples after heating. Infrared imaging was used to determine surface temperatures of hamburgers. Water diffusion in a hamburger bun was examined by an NIR water measurement system. The effect of salt content (two types of salt), geometry and placement of food components, as well as the type of tray on heating uniformity of food were investigated. A consumer panel was used to examine how temperature affected the pleasantness of meal components and how the more or less uneven temperature distribution of microwave heated meals was perceived.
