Vinegar Production by the Static Fermentation of Subcritical Water-Treated Mixtures of Sake Lees and Rice Bran

Abstract Sake lees and rice bran are major by-products of the Japanese food industry and are discarded in large quantities, so it would be helpful to develop sustainable approaches to utilize these feedstocks. We investigated the production of vinegar through static fermentation using a mixture of subcritical water-treated sake lees and rice bran. Subcritical water treatment was previously shown to promote the liquefaction of these by-products to provide solutions rich in amino acids and minerals. Here, we varied the mixing ratios of subcritical water-treated sake lees and rice bran solutions to examine the effect on vinegar production. The amino acid and mineral content of the vinegar changed depending on the mixing ratio, with a higher proportion of sake lees increasing the amino acid concentration, while a higher proportion of rice bran increased the carbohydrate and mineral content. This study proposes a method for producing vinegar with high nutritional value comparable to conventional products by reusing by-products from the food industry.