Factors affecting vinegar metabolites during two-stage fermentation through metabolomics study

Vinegar has long been used as condiment, food seasoning, preservative, and beverage. Vinegar is rich in nutrients and bioactive compounds produced during two-stage of alcoholic fermentation (AF) and acetic acid fermentation (AAF). In order to control the production of nutrients and bioactive compounds in vinegar, it is important to evaluate the contribution of two-stage fermentation to the final metabolite content. Therefore, a GC/MS-based metabolomics approach was used to identify factors that have a greater effect on the content of tomato vinegar metabolites during AF and AAF. The metabolite profiling during vinegar fermentation revealed that the levels of ethylene glycol, malonic acid, glutamic acid, glutaric acid, linoleic acid, butyric acid, and glycerol monostearate were more affected by AAF than AF. For example, the levels of lactic acid were more affected by AF (93.8%) than by AAF (6.2%), while the levels of glutamic acid were less affected by AF (3.0%) than AAF (97.0%). The production of final metabolites in vinegar also depends on the strain of yeast and acetic acid bacteria, and the temperature of AF and AAF. These results suggest that the content of each metabolite contained in vinegar can be changed to the desired level by controlling the fermentation conditions.