Hydration Model of Starchy Foods Heated by Microwave Oven and Conductive Dry Heater

Abstract

The phenomena have often seen that some foods heated with microwave become more soft as if treated with steam though their water contents have decreased due to water evaporation, and so that microwave oven is used for the cooking or food processing such as boiling, steaming, roasting, frying, and even drying. In this paper, the bound water of starch-water mixtures was determined under four heating conditions, and the relation between changes in bound water and total water movements was examined to provide a basic understanding of the mechanisms of heating.
1) Bound water contents induced by sealed heating method were hold greater levels and showed larger changes than those of open heating method.
2) Bound water contents induced by microwave heating were different from those of conductive one under a certain limited range of total water.
The variation of the amount of bound water accompanied with total water would be contributed by the behavior of bound water in addition to the changes of water distribution resulting from the difference of water mobility. Based on the above conclusion, hydration model by four types of heating is proposed.