Conversion of ferulic acid to 4-vinyl guaiacol by yeasts isolated from unpasteurised apple juice

Yeasts were isolated from unpasteurised apple juice on potato dextrose agar supplemented with tartaric acid and on malt extract agar containing chloramphenicol. Isolates were screened for feruloyl esterase and ferulic acid decarboxylase activities. Strains of Rhodotorula rubra, R minuta and Candida lambica produced both enzymes. Ferulic acid decarboxylase activity, resulting in the formation of the off‐flavour 4‐vinyl guaiacol, was highest for the C lambica isolate. This decarboxylase activity was associated with the washed resting cells. The crude enzyme showed temperature and pH optima of 35°C and 6.5, respectively. © 1999 Society of Chemical Industry