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Influence of Rice Proteins on Eating Quality of Cooked Rice and on Aroma and Flavor of Sake

¹Kizakura Sake Brewing Co. Ltd., 223 Shioyamachi, Fushimi-ku, Kyoto 612-8046, Japan. ²Corresponding author. Phone: +81-75-611-4101. Fax: +81-75-622-3510. E-mail: furukawa@kzkappa.co.jp ³Laboratory of Genetic Engineering, Faculty of Agriculture, Kyoto Prefectural University, Shimogamo, Kyoto 606-8522, Japan. ⁴Phytoculture Co. Ltd., 5-18-14 Sekime, Jyoto-ku, Osaka 536-0008, Japan. ⁵Division of Basic Research, Kyoto Prefectural Institute of Agricultural Biotechnology, 74 Seika, Kyoto 619-0244, Japan.

An improved method for the extraction of storage proteins from rice endosperm under conditions safe for producing food was developed. The contribution of the protein extracts to the eating quality of cooked rice and to the aroma and flavor of sake was examined. Sensory analysis was performed to evaluate the eating quality of cooked rice enriched with the protein extracts. Prolamin-enrichment increased the hardness of cooked rice, and glutelin-enrichment degraded the appearance of cooked rice. Physical analyses confirmed that prolamin-enrichment changed, whereas the glutelin-enrichment did not change the physical properties of cooked rice. Light and scanning electron microscopy of rice protein extracts revealed small particles of the prolamin extract and larger aggregated particles of the glutelin extract; these features remained after heating. The aroma and flavor of sake were negatively affected by the addition of the protein extracts. Especially, addition of prolamin significantly lowered the evaluation score of the aroma obtained by sensory analysis.