Ligustrazine formation in Zhenjiang aromatic vinegar: changes during fermentation and storing process

BACKGROUND: Zhenjiang aromatic vinegar is one of the most well‐known traditional fermented vinegars in China. Previously, a alkylpyrazine named ligustrazine was found as a bioactive compound in Zhenjiang aromatic vinegar. However, the generating mechanism of ligustrazine during the fermentation and storing process of vinegar was unknown. In this study, the changes in ligustrazine and its synthesis precursors (diacetyl and acetoin) in the industrial process were investigated by gas chromatography–mass spectrometry. RESULTS: During the fermentation process, ligustrazine was first detected at the fifth day, and content reached 75.90 µg g^?1 when fermentation was complete. During the storage process, the content of ligustrazine increased with storage time, and the content in 6‐year‐old vinegar reached 696.63 mg L^?1, which was about 20 times higher than raw vinegar (34.7 mg L^?1). This may be attributed to the conversion of precursors to ligustrazine through the Maillard reaction as precursor contents decreased during the storage process. CONCLUSION: Results of this study showed that ligustrazine in vinegar was mainly formed during the storage process, and the fermentation process was regarded as the accumulation stage of precursors for ligustrazine synthesis. Copyright © 2011 Society of Chemical Industry