Changes in bioactive and volatile aroma compounds in vinegar fermented in a rotary drum bioreactor

The traditional fermentation of Chinese vinegar is characterized by low mechanization degree, resulting in great demands on the labor force and low production efficiency. Bioreactors present an alternative route to enhancing vinegar production. In this study, we investigated the changing dynamics in the major quality indicators of vinegar during solid-state vinegar fermentation using a rotary drum bioreactor (RDB) and traditional fermen-tation (TF). The bioactive and volatile aroma compounds generated by both methods were determined and compared. Our analysis revealed identical trends in the alcohol, reducing sugar, total acid, and amino nitrogen contents obtained using both fermentation methods. The total acid content of raw vinegar produced in the RDB was 5.1% higher than that produced by TF, and the fermentation cycle was 6 days shorter. The main organic acids detected were acetic and lactic acid, and the total phenolic, flavonoid, ligustrazine, acetoin, and diacetyl levels tended to increase in the RDB. Gas chromatography-mass spectrometry analyses showed that the main volatile flavor components (VFCs) were identical for both fermentation methods. In particular, we detected 64 and 60 VFCs after RDB fermentation and TF, respectively. The major VFCs detected in the early, middle, and late fermentation periods were alcohols, esters, and acids, respectively. These results indicate that the RDB showed better fermentation performance than that of TF, thereby demonstrating considerable potential for producing high-quality vinegar in industrial applications.