Proteolysis in the protein rest of mashing - an appraisal.

Lewis, M.J., Robertson, I.C. and Dankers, S.U.

Abstract
Because of the importance of proteins and polypeptides in determining beer foam quality and susceptibility to haze, and of amino acids in fermentation, an understanding of the effects of mashing conditions on the levels of these substances in wort is of considerable value to the brewer. Investigations are described in which the authors confirmed the presence of both soluble and insoluble proteases in malt, which in the prolonged mashing of thick liquor/grist mixtures made with all malt grist produced increased levels of free amino nitrogen (FAN) in wort by the breakdown of dialysable peptides and polypeptides. Proteins, largely unaffected by these enzymes, precipitated out as the mash temperature increased, possibly affecting wort separation. In shorter and more dilute mashes, which more closely resembled the usual mashing process in US commercial breweries, little or no increase in FAN was observed, leading to the conclusion that the FAN content of industrial worts is largely determined by that of the malt before mashing.
Keywords : free amino nitrogen malt mashing proteolysis