Developmental expression of amylases during barley malting

Amylase activity and qualitative changes in amylase isoenzymes as a function of barely seedling age were investigated in 10 Brazilian barley cultivars. All cultivars showed few isoenzymes in early germination. An increase in general activity ensued in the following days when new isoenzymes were detected and those already observed since early germination had their activity increased. All cultivars disclosed increase in amylase activity until the third or fourth day of germination. Some cultivars maintained this high activity until the last day analysed. other cultivars presented a decrease in activity in the fifth or sixth day. No electrophoretic pattern or allelomorph responsible for a higher amylase activity was detected. Beta-amylase activity was always superior to alpha-amylase activity. High beta-amylase activity was already observed on the second day of germination while alpha-amylase activity began to increase only from the third day on. The results obtained suggest that, at least for the cultivars analysed, there is a high general amylase around the fourth day of germination, indicating that germination could stop at this moment, ensuring that hydrolitic enzymes activity required in the brewing process is met. Beta-amylase was lightly correlated with diastatic power (r = 0.565) but no correlation was observed between alpha-amylase and diastatic power (r = -0.128), or neither between alpha- and beta-amylase with malting quality (r = 0.153 and r = -0.348, respectively). These results indicate that beta-amylase activity in barley grains, more than alpha-amylase, can be a good predictor of diastatic power. (C) 2001 Academic Press.