Tracking volatile flavor changes during two years of aging of Chinese vinegar by HS-SPME-GC-MS and GC-O

Aging is an essential step for enriching the aroma profiles of Chinese vinegar. This study aimed to track the volatile flavor changes in the same batch of Chinese vinegar for the first time during two years of aging with the aid of HS-SPME-GC-MS. The aroma-active compounds were characterized at 0, 6, and 12 months of aging using GC-O coupled with a modified frequency method. A total of 67 volatile compounds and 30 aroma-active compounds were identified during the different stages of aging. Most alcohols, esters, ketones, acids, and phenols decreased during the aging from 628.4, 105.4, 132.1, 22.1, and 21.4 mu g/L at 0 month to 228.7, 7.2, 9.69, 17.24, and 11.6 mu g/L at 24 months separately, except aldehydes and pyrazines, which showed slight increases. Many aroma-active compounds were generated during the aging, such as methional, trimethylpyrazine, acetophenone, and 2-acetyl-3-ethylpyrazine, while pyrazines were formed during 24 months of aging. Three aroma-active compounds with high odor activity values (OAVs) showed significant contributions to the aroma profile of vinegar, which included isovaleric acid (2743, 340, and 3139), 4-ethylguaiacol (580, 429, and 516), and gamma-nonalactone (324, 640, and 442) at 0, 6, and 12 months of aging, respectively.