Aggregation of Protein and Precipitation by Polyphenol in Mashing. M. J. Lewis and J. W. Serbia, Department of Food Science and Technology, University of California, Davis 95616. J. Am. Soc. Brew. Chem. 42:0040, 1984.

In a grain-out mashing system that contained 0.900 mg/ml of dissolved protein, 0.400-0.500 mg/ml of protein precipitated close to the conversion temperature of 70° C; this precipitation was accompanied by a decrease in total phenols of about 0.100 mg/ml, measured as gallic acid. Protein precipitation in the mash depended on the presence of polyphenols from malt; when polyphenol was partially removed, the amount of protein precipitating at 70° C was substantially reduced. Adding 0.100 mg/ml of gallic acid back to low-polyphenol grain-out mashes caused the mash to again precipitate 0.400 mg/ml protein at 70° C but not below. In low-polyphenol mashes, the mashing process appeared to create protein molecules that were larger than usual. A combination of protein aggregation and high temperature appeared to be necessary for the precipitation of protein by polyphenol during mashing.

Keywords: Aggregation, Malt, Mashing, Polyphenol, Precipitation, Protein