Significant contribution of amino acids to antioxidant capacity of Japanese rice wine (sake)

Various antioxidant components have been reported in Japanese rice wine (sake), while the contribution ratio of each component to the antioxidant capacity of whole sake has not been well understood. In this study, we evaluated the radical absorption capacity (H-ORAC and/or DPPH radical scavenging ability) and antioxidant components of commercially available sake, and estimated the major components contributing to antioxidant capacity.

Water-soluble components with a molecular weight of less than 3000 contributed more than 90% to H-ORAC of sake by measuring the ultrafiltered fraction. The Maillard reaction seemed to have little influence on H-ORAC by browning experiments. The radical absorption capacity of sake showed a strong positive correlation with the amounts of four antioxidant amino acids (Cys, Met, Tyr, Trp) and two phenolic acids (ferulic acid and p-coumaric acid). Evaluating H-ORAC of a sake model solution composed of these antioxidants revealed that the four amino acids showed a clearly higher contribution (25.7-58.2%) than the phenolic acids. In addition, there was a slight synergistic effect when the four amino acids were mixed, whereas such effects were not seen when mixed with the phenolic acids and other sake major components (organic acids, glucose and ethanol).

We concluded that the contribution of free amino acids to the radical absorption capacity is quite important in sake. These findings will provide a new perspective for antioxidant researches of sake and many fermented foods. © 2024 Society of Chemical Industry.