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Abstract
The successful construction by hybridization or spheroplast fusion of novel brewing-yeast strains that possess the ability to utilize wort dextrins was previously hampered by the presence of a compound in the beer characterized by an unpleasant “phenolic” or “clovelike” aroma. Brewer's yeasts have been reported incapable of decarboxylating wort ferulic acid to 4-vinyl guaiacol, the compound deemed responsible for “medicinal” or “phenolic” off-flavor. A survey was made of 22 yeast strains of varying genera and species, and all Saccharomyces diastaticus strains tested produced 4-vinyl guaiacol in significant amounts during a 72-hr wort fermentation. Production of this phenolic off-flavor has been ascribed to the presence of a single dominant nuclear gene designated POF. Hybrids were constructed that exhibited glucoamylase activity and lacked the ability to decarboxylate ferulic acid. Fermentations with these hybrids resulted in superattenuated worts and palatable beers.