Germination of wheat grains at various temperatures in relation to the activities of α-amylase and endoprotease

Germination percentages of wheat grains sampled at 3 grain-filling stages : yellow-ripe stage (water content 45-50%), dough-ripe stage (35-40%), and full-ripe stage (25-30%), and imbibed in water at 12 degreesC and 20 degreesC were examined in relation to the activities of alpha-amylase and endoprotease. Wheat varieties studied were Chihoku-komugi, which is susceptible to pre-harvest sprouting, and Satanta, which is resistant. Germination percentage was higher at 12 degreesC than at 20 degreesC in all grains sampled at all stages in both varieties, and was higher in Chihoku-komugi than in Satanta at 20 degreesC. The activity of alpha-amylase in the grains at the yellow-ripe stage was higher at 12 degreesC than at 20 degreesC in both varieties, but that at the other 2 stages was higher only in Satanta. Endoprotease increased rapidly from 7 to 10 days after the start of imbibition, and exceeded 12 units only at 12 degreesC in Chihoku-komugi grains at the dough and full-ripe stages. The results showed that alpha-amylase activity was lower than the value equivalent to 300 brabender unit (BU) in amylography when the germination percentage was 0%. Endoprotease activity exceeded 6 units when the germination percentage exceeded 90%.