VIEW ARTICLE    DOI: 10.1094/ASBCJ-44-0040

The Protein Character of Beer is Defined in the Brewhouse. Charles K. Huston, Jr., Sang-Suk Oh, and M. J. Lewis, Department of Food Science and Technology, University of California, Davis, CA 95616. J. Am. Soc. Brew. Chem. 44:0040, 1986.

The behavior of proteins during mashing was examined using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) to separate protein subunits. Proteins dissolved at somewhat different rates during the "protein rest" stage of mashing to yield a typical and reproducible SDS-PAGE pattern by the end of this period. Sephadex gel filtration (followed by SDS-PAGE) of selected fractions suggested that some of the subunits were substantially aggregated in the wort. Protein subunits precipitated at different rates and to different extents during the remainder of the mash temperature program, and wort at the end of mashing was generally dominated by only two subunits in the molecular weight range of 30,000 to 40,000 (plus some presently uncharacterized material at or below 16,000). Subunits lost during mashing could be recovered in the redissolved precipitated protein, although the precipitate also contained irreversibly aggregated high-molecular-weight species. Such species also appeared after mashing in polyvinylpyrrolidone-treated wort; this treatment also prevented the precipitation of any subunits originally dissolved during the protein rest. Gallic acid (but not tannic acid, which had general protein-precipitating action) added to polyvinylpyrrolidone-treated wort caused selective protein precipitation similar to that caused by the mash temperature program. After boiling there were only two major protein subunits remaining in the wort; these remained unchanged through fermentation and finishing and were present in all the commercial beers we examined.

Keywords: Beer, Haze, Mashing, Precipitation, Protein, Wort