Identification of Characteristic Volatiles in Vinegar Prepared with Monascus-fermented Rice during Acetic Acid Fermentation Using Multivariate Statistical Analysis

An electronic nose, gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O) were used to explore the changes of aroma compounds in vinegar prepared with Monascus-fermented rice during its acetic acid fermentation process. Different multivariate statistical analysis, such as cluster analysis, principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were used to investigate the differences in volatile compounds between different stages of fermentation and to identify the characteristic volatile components. The results showed that the electronic nose could clearly discriminate samples from different acetic acid fermentation stages. A total of 54 volatile compounds were identified by GC-MS and GC-O during the acetic acid fermentation process. The characteristic aroma components were n-octanol, isobutanol and ethyl valerate for the early stage; benzoic acid, ethyl palmitate, n-hexanol, 2,4-di-tert-butylphenol and ethyl lactate for the middle stage; propyl acetate, ethyl lactate and isobutyl acetate for the mid-tolate stage; L(+)-2,3-butanediol and ethyl heptanate for the late stage. The results of this study provide a theoretical basis for aroma regulation and flavor improvement of vinegar prepared with Monascus-fermented rice.