Influence of polishing ratio on the rice brewing characteristics and the flavour quality of sake

Abstract

The rice polishing ratio has an essential effect on the flavour quality of sake. This study comprehensively describes the relationship between the polishing ratio and sake quality. As the polishing ratio decreased, the outer layer of rice suffered more structural damage. Moisture was more readily accessible to the interior of the rice. The pasting properties of the rice were significantly improved, resulting in a more complete fermentation. The above results decreased the aldehydes and ketones content in steamed rice from 65.61 μg/mL to 51.82 μg/mL, leading to a reduction of off-flavours caused by their over-accumulation. The polishing ratio also had a significant effect on sake flavour. A lower polishing ratio reduced higher alcohols, like 3-methyl-1-butanol. The flavour perceived in the sake changed from herbal to alcohol aroma. The final results showed that the flavour compounds in the sake were highest when the polishing ratio was 50%. Among them, the contents of key flavour compounds such as ethyl acetate and ethyl caproate were peaked. And the content of bitter amino acids was low. Therefore, rice with a polishing ratio of 50% is the most suitable for sake brewing. The results of this study provide a scientific basis for the accuracy of rice processing in sake brewing.