Quantitative Isoelectric Focusing of Wort and Beer Proteins¹

1 Presented at the 45th Annual Meeting, Portland, OR, April 1979.

Abstract

A method is described for quantifying isoelectric focusing of proteins in wort, beer, and related samples on polyacrylamide gel rods. Detection linearity is demonstrated, and the procedure for calculating peak height variances is explained. These variances are used for hypothesis testing using the chi-square statistic. With this statistic, tests can be made for significant differences between the same band or peak of two different samples or for significant differences overall between two samples. The focused proteins are also divided into an acidic group and a basic group of proteins, using an isoelectric pH of 6.7 as the dividing point. The statistical procedure used to test for significant differences in acidic or basic proteins between two samples is also explained. These techniques are used to examine experimental beers produced from a spectrum of high Plato worts. Quantities of acidic proteins were lower in these beers than in beers produced from 12™ Plato worts. In addition, a loss in acidic proteins occurs in beer, compared with the wort from which it was produced, and this loss is directly proportional to the wort acidic protein concentration. Basic protein losses appeared to be random.

• Acidic proteins
• Basic proteins
• Beer
• Isoelectric focusing
• Statistical quantitation
• Wort

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