Influence of sprouting conditions on compositional changes and techno-functional properties of adzuki bean (Vigna angularis) flours

Germination is a biotechnological strategy capable of inducing metabolic changes that modify the chemical composition and functional properties of pulses. This study evaluated the effect of germination conditions on the compositional and techno-functional characteristics of adzuki bean (Vigna angularis) flours. Grains were soaked and germinated at different temperatures (20 or 25 °C) and time periods (72 or 120 h). After drying and milling, the germinated flours (GF20-72, GF20-120, GF25-72, and GF25-120) were compared with ungerminated adzuki flour (UGF). Proximate composition, α-amylase activity, reducing sugars, free amino acids, dietary fiber, phytic acid, condensed tannins, and RVA pasting properties were evaluated.

Germination promoted the mobilization of starch reserves, as evidenced by a reduction in starch content from 41 to 36 g/100 g, together with up to a 12-fold increase in α-amylase activity and a 45% increase in reducing sugars. The most pronounced effects were observed in GF25-120. These changes were associated with a marked reduction in pasting parameters. Peak viscosity decreased from 1123 cP in UGF to 460 cP in GF25-120, representing a reduction of nearly 60%. Although total protein content remained unchanged, free amino acid levels increased by up to 94%, with the highest values observed in GF25-120. In addition, germination reduced insoluble dietary fiber content by up to 30% and condensed tannin content by up to 60%, whereas phytic acid reduction was condition-dependent, with the lowest levels observed in GF20-120.

In conclusion, germination enhances the metabolic activity of adzuki beans, leading to changes in their chemical composition and the techno-functional properties of the resulting flours. The observed modifications suggest that these flours may represent promising functional ingredients with the potential to improve nutrient availability during digestion.