Advanced method for measuring proteinase A in beer and application to brewing

Proteinase A, excreted from yeast cells into beer during fermentation in th e brewing process, has been shown to degrade foam-active proteins and to de crease foam stability. In order to improve the measurement of this enzyme i n beer, a new fluorescent peptide, MOCAc-Ala-Pro-Ala-Lys-Phe-Phe-Arg-Leu-Ly s (Dnp)-NH2, wits synthesised and applied to the accurate and rapid estimat ion of proteinase A in commercial beer and fermenting wort. This novel subs trate is several hundred times more sensitive to proteinase A than other pr eviously reported synthetic substrates or native protein substrates. The co ncentration of proteinase A in: beer is closely related to foam stability a nd proteinase A activity was found to increase gradually during fermentatio n. The concentration of proteinase A excreted from yeast cells is also clos ely related to the vitality of pitching yeast cells. This new method was su ccessfully applied to the evaluation of yeast vitality and the development of optimum yeast handling procedures.