Article ID: 20J01
The enzyme digestibility of steamed rice grains is an important characteristic for sake brewing and is higher when the pasting temperature is lower. On the basis of a low pasting temperature measured by a Rapid Visco Analyzer, we selected ‘Akitasake 44’ from among 41 improved cultivars and lines used in sake brewing. Analysis of its amylopectin chain length distribution shows that it is richer in short-length chains (degree of polymerization 6–12) and poorer in mid-length chains (degree of polymerization 13–24) than the commonly preferred cultivars ‘Akitakomachi’, ‘Gohyakumangoku’, and ‘Okuhomare’. ‘Akitasake 44’ lacked activity of phosphorylase 1, an enzyme related to starch metabolism in the endosperm. Although phosphorylase 1 activity was normal in its ancestry, ‘Akitasake 44’ was bred by gamma-irradiation of ‘58kei3071’. Sequence analysis revealed a single nucleotide substitution in the 12th exon of the phosphorylase 1 gene of ‘Akitasake 44’, which caused an amino acid substitution. This mutation is the likely cause of the lack of phosphorylase 1 activity, and consequently the lower pasting temperature of ‘Akitasake 44’.
