ROLE OF STARCH AND GLUTEN ON STALING OF WHITE BREAD TREATED WITH MICROWAVE-HEATING

Bread heated with microwave is well known to be rapidly stale. This rapid staling was never observed on bread heated by ordinary thermal treatment. Staling mechanism of bread heated with microwave has not been fully understood due to its complexity, although some studies have been reported on changes in the starch-gel and the bound water in bread. In this study, the role of starch and gluten on staling was investigated for white bread treated with microwave-heating. In order to elucidate staling mechanism more precisely, we have used breads, starch-gel and gluten-gel with/without monoglyceride. The results are summarized as follows: (1) The rapid hardening of microwave-heated bread was mainly caused by hardening of starch, of which a main factor was the changes from sol to gel on starch in bread. (2) Crystallization (retrogradation) of starch in bread contributed greatly to the gradual hardening after rapid hardening in the primary process. (3) Starch and gluten were both concerned as well with a decrease in crispy property of bread after microwave heating. Gelatinization and elution of starch, and reinforcement of gluten network caused the decrease of its crispy property.