Effects of Increase in α-Amylase and Endo-Protease Activities during Germination on the Breadmaking Quality of Wheat

Abstract

The effects of increase in α-amylase and endo-protease activities during germination on the deterioration of the breadmaking quality of hard wheat were examined using three varieties with different strengths of gluten: VictoriaINTA, Harunoakebono, and Leader. The results are summarized as follows: (1) The degradation of the breadmaking quality of flour damaged in germination differed greatly according to the gluten strength of each variety. VictoriaINTA, which has extra-strong gluten, was more tolerant of the germination damage than the other varieties with strong gluten. (2) The degradation of specific loaf volume, which is caused by lowering the gas retention of the dough, was the result of the softening of the dough that was observed as a decrease in the mixing peak time and the breaking force of the dough. (3) The α-amylase and endo-protease activities of flours did not seemed to influence the breadmaking quality, although there was a considerably high correlation between endo-protease activity of whole wheat flour and breadmaking quality. From these results, it would seem that the main reason that flour damaged during germination degrades breadmaking quality is the endo-protease in the wheat grain, which already causes partial gluten decomposition. Accordingly, it might be better to examine the endo-protease activity of whole wheat flour at harvest ripeness in order to estimate the value of breadmaking quality within the hard-wheat breeding system.