The Properties and Brewing Performance of Brewing Yeasts Possessing Killer Character. T. W. Young, British School of Malting and Brewing, Department of Biochemistry, University of Birmingham, P.O. Box 363, Birmingham B15 2TT, UK. J. Am. Soc. Brew. Chem. 41:0001, 1983.

The properties of the yeast toxin produced by strains of a commercial brewing yeast genetically manipulated to possess killer character (brewing killers) are indistinguishable from those of the parent killer strain. Gas chromatographic analysis of head-space samples of beers shows that beers produced by genetically manipulated strains BK1 and BK2 and by the nonkiller brewing yeast parent contained similar amounts of ethyl and isoamyl acetate esters, propan-1-o1 and 2-methyl butan-1-o1. The concentration of diacetyl was also indistinguishable in beer produced using BK2 and control beer. Beers derived from both brewing killer strains contained significantly lower amounts of 2-methyl propan-1-ol when compared to control beers. In fermentation, the performance of the genetically manipulated strains is essentially the same as that of the brewing yeast parent. The beers produced have gross analytical values similar to those of beers produced using the nonkiller brewing yeast parent. Furthermore, in a three-glass taste test, a panel of 31 individuals was unable to distinguish between beers produced by the genetically manipulated strains and the original brewing yeast.

Keywords: Fermentation, Killer yeast, Saccharomyces, Yeast