Enhancing the Concentration of 4-Vinylguaiacol in Top-Fermented Beers—A Review

Abstract

Despite being considered undesirable in bottom-fermented beers, 4-vinylguaiacol (4VG) is a well-known aroma compound found in top-fermented beers such as Belgian white (brewed with unmalted wheat), German Weizen, and rauch (brewed with malted wheat). Most of the published reports have investigated the brewing technology used to enhance the concentration of 4VG, but only a few have explored the genetic engineering of yeast strains to increase its content. In fact, expressing the phenylacrylic acid decarboxylase (PAD1) and phenolic acid decarboxylase (PADC) genes is the most efficient way to enhance the concentration of 4VG in top-fermented beers. Accordingly, this review focuses on the cloning and expression of PAD1 and PADC genes and compares the concentrations of 4VG in top-fermented beers brewed with parent and mutant yeasts in laboratory-scale mashing and fermentation experiments. The results indicate that the concentration of 4VG was markedly increased in top-fermented beers brewed with the mutant yeast.