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β-Amylase (α-1,4-glucan maltohydrolase; EC 3.2.1.2) is known to be an important enzyme in beer brewing. To identify the contribution of β-amylase in more detail, two β-amylase-deficient barley, 'Backcrossed line (BCL)-Haruna' and 'Nittakei 81', were used for the investigation of malt quality and brewing characteristics. 'BCL-Haruna' was bred by the backcross method for the introduction of the β-amylase-deficient trait from landrace barley ('Tibet Violet 1') to Japanese traditional malting barley 'Haruna Nijo'. 'Nittakei 81' was bred by crossing between Japanese malting barley 'Sukai Golden' and 'Tibet Violet 1'. With regards to the malting quality under 41.0% target cast moisture in micro-malting, the diastatic power (DP) and apparent attenuation limit (AAL) of 'BCL-Haruna' and 'Nittakei 81' were 408 oWK and 416 oWK and 12.4% and 14.8% lower than those of the control variety 'Haruna Nijo'. Oligosaccharide analysis indicated that the maltose concentration of the 'Nittakei 81' wort was 19.7 g/L lower in comparison to a standard European malting barley 'Propino' wort, although the maltotetraose and maltopentaose concentrations of the 'Nittakei 81' wort were 5.6 g/L and 2.7 g/L higher than those of the 'Propino' wort. After fermentation, the alcohol concentration of the 'Nittakei 81' beer was 0.67% lower compared with the 'Propino' beer, and the extract and concentrations of maltotetraose and maltopentaose of the 'Nittakei 81' beer were 5.0 g/L and 2.5 g/L higher than those of the 'Propino' beer. The results indicate that the β-amylase-deficient barley has a unique malting quality, especially lower DP and AAL, which might induce inadequate starch degradation or fermentation. However, this trait caused no serious issues during the brewing process, suggesting the possibility of β-amylase-deficient barley as a unique brewing material including low-alcoholic and non-alcoholic beer production with a specific saccharide composition. [ABSTRACT FROM AUTHOR]

In general, barley with smoother degradation of seed storage material (modification) is known to have lower seed dormancy and a higher risk of pre-harvest sprouting (PHS). The Qsd1 and Qsd2 genes affecting seed dormancy have also been reported to affect malting characteristics. To overcome this situation, barley with an excellent balance of modification and seed dormancy was screened among the mutant population derived from 'Nittakei 68 (N68)'. In the mutant lines screened, 'N68-411' exhibited a moderate seed dormancy similar to that of 'N68', but with higher modification. It was considered that 'N68-411' was mutated in a different gene from Qsd1 and Qsd2 , resulting in no significant change in seed dormancy, only in modification. 'N68-411' also showed rapid modification during germination, suggesting a possibility of shorter germination time in malting process. Analysis of progenies from 12WY375/N68-411 and Xena/N68-411 indicated that the 'N68-411' trait was inherited and associated with a small number of genes. [Display omitted] • Sustainability of barley and malt production. • Discovery of the barley mutant line with novel traits. • Better balance between malt modification and seed dormancy. • Possibility of a shorter germination time in the malting process. [ABSTRACT FROM AUTHOR]