Untargeted metabolomics based on UHPLC-Q-Exactive-MS reveals metabolite and taste quality differences between Koshihikari rice from China and Japan

Koshihikari rice from Japan is a well-known geographical indication rice with excellent taste quality and a high commodity price. However, unscrupulous traders use rice grown in other geographical locations to pass themselves off as Japanese Koshihikari and harms the interests of rice exporters and consumers. Understanding the differences in taste quality and metabolites of Koshihikari rice from various origins can assist people in determining the authenticity of geographical indication rice. In this study, untargeted metabolomics based on UHPLC-Q-Exactive-MS was used to understand metabolite differences in Koshihikari milled rice from China and Japan, and a taste quality analyzer was used to understand taste quality differences in rice. Our results showed that Koshihikari from Japan has lower hardness and higher stickiness after cooking, and the rice has better taste quality. Non-targeted metabolomics identified 520 metabolites. Compared to Koshihikari from Japan, 244 metabolites from South China (Hubei) and 233 metabolites from Northern China (Shandong) were significantly different, and the vast majority of metabolites were down-regulated. The high content of amino acids and lipid metabolites in Japanese koshihikari may have contributed to its excellent taste quality. Our findings provided comprehensive analytical data for distinguishing the metabolite profile for Koshihikari authenticity as well as a better understanding of the taste quality variation of premium rice.