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Influence of Sulfur and Nitrogen Content of Rice Grains on Flavor in Stored Sake

¹National Research Institute of Brewing, 3-7-1 Kagamiyama, Higashihiroshima 739-0046, Japan. ²Corresponding author. Phone: +81-82-420-0812. Fax: +81-82-420-0850. E-mail: okuda@nrib.go.jp

The influence of nitrogen and sulfur compounds in rice grains on changes in flavor in stored sake was investigated using Japanese rice cultivars for sake making. Nitrogen content exhibited a significant positive correlation with sulfur content. Based on the molar ratio of nitrogen to sulfur in the rice grain, the sulfur compounds appeared to be derived from protein-associated sulfur-containing amino acids, as reported previously. The higher the protein content of the rice, the greater the amount of nitrogen and sulfur compounds found in both the digest of steamed rice grains and in the sake. Physicochemical changes were investigated in the stored sake to confirm the influence of total sulfur content. Polysulfides in the stored sake appeared to be higher when made from rice grains of high total sulfur content. Staling of stored sake was affected by levels of protein-associated sulfur-containing amino acids in the rice.