Genetic variation of β-amylase thermostability among varieties of barley, Hordeum vulgare L., and relation to malting quality

To investigate variation in the thermostability of β-amylase among varieties of barley, Hordeum vulgare L., crude enzyme was extracted from the seeds, and the relative remaining activity was calculated after heat treatment. Our results indicated that the varieties tested were divided into three groups (types A, B and C). All the latest Japanese malting varieties showed high themostability (type A), while European, North American and Australian varieties showed intermediate (type B) or low thermostability (type C). Isoelectric focusing (IEF) of β-amylase was also investigated. Type B varieties divided into two subtypes (types B1 and B2) based on two different IEF patterns (types I and II), whereas those of types A and C showed only one IEF pattern (type II). We also examined their thermostability in the varieties based on the pedigrees of the Japanese malting barley. Our results indicated that the thermostability of β-amylase had a close relationship to fermentability for the production of beer. This fact suggests that the thermostability of β-amylase has a significant influence on the malting quality of barley.