Principal Component Analysis and Comprehensive Evalution of Free Amino Acid Composition of Zunyi Characteristic Pickled Peppers Based on Two-fermentation Method

In order to explore the influence of twice fermentation technology on the quality of pickled peppers, the differences in crispness, color, amino acid nitrogen and free amino acids were measured and analyzed by two-fermentation of Zunyi characteristic pickled peppers, and the taste activity value (TAV), principal component analysis (PCA) were used to evaluate the content, composition and flavor diversity of free amino acids in pickled capsicum. The results showed that the amino acid nitrogen content in the four kinds of pickled peppers (fresh, traditional natural primary fermentation for 30 d, twice fermented, traditional natural primary fermentation for 150 d) were 0.05, 0.17, 0.24, 0.18 g/100 g respectively, and the amino acid nitrogen content of the twice fermented peppers was the highest, and the brittleness remained good and the color was bright red. All samples contained 13, 15, 16 and 15 kinds of amino acids respectively, the flavor characteristics were umami amino acid>sweet amino acid>bitter amino acid, and glutamic acid had the greatest effect on the flavor of pickled pepper, with TAV values ranging from 9.67~45.67. Three principal components were extracted by principal component analysis, and the cumulative variance contribution rate was as high as 98.584%, which could better reflect the comprehensive information of free amino acids in the sample, it was found that glutamic acid, threonine, valine, methionine, isoleucine, histidine, arginine, glycine, cysteine, leucine and tyrosine had the greatest influence on the taste of pickled pepper, and the comprehensive score of each principal component obtained the highest comprehensive score of Zunyi characteristic pickled pepper. The comprehensive evaluation found that the quality of free amino acids in Zunyi characteristic pickled pepper was better than that of fresh and traditional natural pickled peppers, which provided a theoretical basis for the improvement of pickled pepper fermentation technology and the artificial control of pickled pepper flavor.