Ferulic Acid Release and 4-Vinylguaiacol Formation during Chinese Rice Wine Brewing and Fermentation

Abstract

The release of ferulic acid (FA) and the subsequent enzymatic decarboxylation to 4-vinylguaiacol (4-VG) were nearly ubiquitous during the production of Chinese rice wine. To evaluate the release of FA and the transformation to 4-VG, the levels of FA and 4-VG were determined by high performance liquid chromatography (HPLC) and gas chromatography-mass spectrum (GCMS), respectively. During rice wine brewing, the concentrations of FA and 4-VG increased as fermentation time prolonged, with a rapid rise in days 1 to 5 of the main fermentation and followed by a slower rise from the 6th day post inoculation. FA and 4-VG levels in mashes, fermented by yeast with wheat Qu, were significantly higher than those in mashes fermented by yeast using commercial enzyme additions. The release of FA from rice by wheat Qu involves an enzymatic release mechanism. The levels of FA and 4-VG from rice flour by wheat Qu rose gradually during the first 24 h and then tended to stabilize. The capacity of yeasts to decarboxylate phenolic acids (Pof + phenotype) was absent in most rice wine brewing yeasts. These results suggest that the production of FA and 4-VG originated from materials in the wheat Qu rather than by the yeast during Chinese rice wine brewing and fermentation.