Enzymatic Saccharification Behavior and Compositional Characteristics of Mucuna pruriens-Based Amazake: A Comparison...

Amazake is a traditional Japanese non-alcoholic beverage produced through enzymatic saccharification using rice koji. Conventional rice-based amazake contains high levels of glucose derived from starch saccharification, prompting interest in alternative plant-based substrates with distinct sugar compositions and nutritional characteristics. However, research on amazake produced from non-rice substrates remains limited. In this study, amazake produced entirely from Mucuna pruriens beans was evaluated and compared with conventional rice amazake to assess its feasibility and fundamental compositional properties. Mucuna beans were subjected to prolonged thermal treatment (90°C for 16 h), followed by homogenization, prior to saccharification with rice koji. Changes in L-3,4-dihydroxyphenylalanine (L-DOPA) content, saccharification behavior, sugar composition, and antioxidant-related indices were examined. Preprocessing reduced the intrinsic L-DOPA content from approximately 3 g/100 g (wet basis) in raw beans to below 0.04 g/100 g, with a further decrease observed after saccharification. Although Mucuna bean amazake exhibited lower soluble solids and reduced sugar formation than rice amazake, time-course analyses of Brix, reducing sugars, and sugar composition confirmed steady saccharification. These results indicate detectable and progressive enzymatic hydrolysis despite the structural resistance of legume starch. Notably, distinct sugar distribution patterns, including low-degree-of-polymerization sugars and α-1,6-linked oligosaccharides, were observed during saccharification, highlighting qualitative differences in sugar composition beyond total sugar content. In addition, Mucuna bean amazake exhibited consistently higher antioxidant-related indices, including DPPH radical scavenging activity, total phenolic content, and ferric reducing antioxidant power, than rice amazake throughout saccharification, likely reflecting the release of bound phenolics and generation of antioxidant peptides from the Mucuna matrix. These findings provide baseline compositional evidence supporting the feasibility of M. pruriens as a novel plant-based substrate for amazake production.