Evaluation of the Flavor Characteristics of Vinegar from Different Sichuan Regions Based on Chemical Analysis and Intelligent Sensory

The objective of this study was to compare and analyze the quality of four kinds of traditional vinegar from Sichuan Province. Through chemical analysis methods such as automatic amino acid analyzer, high-phase liquid chromatography (HPLC) and solid-phase microextraction gas-phase-mass-spectrometry (SPME-GC-MS) technologies were used to determine and analyze the types and contents of amino acids, organic acids, and volatile organic compounds (VOCs). Finally, in addition to sensory analysis, intelligent sensory such as electronic nose and electronic tongue combined with principal component analysis (PCA) and cluster analysis (CA) were used for characterization. The results showed that: The pH and total acid ranges of the Sichuan vinegar samples were from 3.08 to 3.29, and 16.40% to 18.07%, respectively. The color parameter a^* and b^* values were tested to be significantly different (P<0.05). A total of 17 kinds of amino acids were detected, of which alanine and glutamic acid had the highest content. Among 9 organic acids tested, including acetic acid and tartaric acid, the total organic acid content was 22.44～70.06 mg/mL, of which acetic acid and lactic acid ac-counted for more than 50% of the total organic acids, and Zigong vinegar had the highest organic acid content (70.06 mg/mL). More than 150 volatile organic compounds were detected in the experiment, of which acids (21.56%～44.34%) were the most abundant. It was found that the types and relative contents of unique flavor substances in traditional Chinese vinegar, such as esters and benzodiazepines, were found in Meishan vinegar, and it was significantly higher than Zigong and Nanchong vinegar samples. The sum of the first two principal components of PCA of electronic nose and electronic tongue was more than 98% of the cumulative variance. The difference of CA analysis between Zigong vinegar and Meishan vinegar was mainly due to the degree of astringency in sensory evaluation and the number of ketones and heterocycles in volatile organic compounds. The difference of CA of electronic tongue was mainly caused by the difference of pH, total amino acid, essential amino acid, organic acid and total acid between Zigong, Meishan and Nanchong vinegar. Chemical analysis, sensory evaluation and intelligent sensory combined with chemometric method can be used to characterize the correlation of four Sichuan vinegar samples due to differences in raw materials, processes, formulas, etc. This article can provide a practical reference for establishing a reliable characterization of Chinese vinegar, provide an effective tool for the evaluation of vinegar quality and authenticity, and help to understand the relationship between the internal and external quality characteristics of vinegar.