| Soy sauce was originated from China.As a traditional fermented condiment and potential function food,it has been eaten worldwide,especially in Asian countries.Soy sauce is made from soybean(defatted soybean),wheat and/or wheat flour and/or wheat bran through microbial fermentation,and comprised of many beneficial metabolites such as free amino acids,sugars,organic acids,aromatic compounds.These metabolites provide unique flavor and nutrition.Nowadays,Japanese soy sauce with high quality occupied a large number of high-level markets in China.The price of Japanese soy sauce is average3-6 times that of Chinese soy sauce.However,there are few reports on the metabolites,especially analysis of metabolites in soy sauce using mass-based spectrometry or nuclear magnetic resonance methods.The purpose of this study was to investigate the composition of four soy sauces(two sauces produced from China and another two sauces produced from Japan)by using UPLC-ESI-QTOF-MS and NMR.It was expected to find the main differential metabolites in above soy sauces,and to provide a theoretical basis and methodological reference for clarifying and analyzing the metabolites between Chinese and Japanese soy sauces.The main conclusions are as follows:1.UPLC-ESI-QTOF-MS analyses revealed that the major differences between Chinese and Japanese soy sauce were 175.1/497(mz/RT)and 183.1/50(mz/RT)at MS1level,respectively,which were arginine and harmane further identified by MS/MS data.2.The relative content of arginine and harmane in Japanese soy sauce are significantly higher than in Chinese soy sauce.Among them,the relative abundance of arginine were 3.42×10~7 and 3.32×10~7 in JS1 and JS2,respectively,which were significantly higher than in CS1 and CS2(0.98×10~7and 1.72×10~7),and the harmane in JS1 of Japanese soy sauce were 2.02×10~7,which were significantly higher than that in CS1 and CS2(1.16×10~7and 0.84×10~7).3.Arginine can be used as a useful marker to accurately discriminate the four kinds of Chinese and Japanese soy sauces with the accuracy of 99.8%.4.Compared with the results of QTOF-MS identified by open source software XCMS,the MS-DIAL software identified 183.1/50(mz/RT)substance,namely,alkaloid Harmane.5.Based on NMR data analysis,the sugar content of CS2 in Chinese soy sauce including mannose,fibrous disaccharide,glucose-6-phosphate,arabinose,fructose,trehalose and galactose was significantly higher than the other three ones.It is further confirmed that high sugar content may lead to the decline quality of soy sauce,which is consistent with the results of previous report. |
