Distribution of phenolic yeasts and production of phenolic off-flavors in wine fermentation

The activity of wine yeasts to decarboxylate ferulic and p-coumaric acids i s one of their biological properties related to the production of phenolic off-flavors (POF) in winemaking. We examined POF productivity in 116 strain s of wine yeast, 74 strains of wild yeast (Saccharomyces cerevisiae) and 23 strains of non-Saccharomyces yeast, and found that a majority of these yea sts were POF-producing strains. The frequency distribution of POF-producing strains was 81 to 95% in wine yeasts, 85 to 97% in wild yeasts and 78 to 8 3% in non-Saccharomyces yeasts based on the POF test with addition of ferul ic and p-coumaric acids to grape Juice medium. The Rhodotorula, Candida, Cr yptococcus, Pichia, Hansenula, and Brettanomyces strains had high or modera te POF productivity among the 20 non-Saccharomyces species. The decompositi on rate of ferulic acid correlated with POF production and the critical con centration of phenolic acid (free form) in grape must was estimated to be m ore than 10 mg/l. Segregation of POF phenotype and Southern blot analysis o f phenolic wine yeasts suggest that POF production is controlled by the POF gene (PADI). The results showed the frequent distribution of phenolic yeas ts in the winemaking environment. These suggest the importance of controlli ng POF production by using wine yeast strains of low POF productivity. The grapes must be prepared by a suitable process to prevent the increase in ph enolic acid content.