Influence of precipitation of malt proteins in lautering.

Lewis, M.J. and Oh, S.S.

Abstract
A model lauter tun was used in the study of malt protein precipitation during lautering. Protein deposition during mashing and cold water extraction was followed by measuring protein concentration (Bradford procedure) and haze formation. The effects of specific gravity and protein concentration on run-off and of mash temperature on the solution and precipitation of protein were studied for both infusion and temperature programmed mashing. In temperature programmed mashing a 2-6 lb/barrel protein containing precipitate was formed that accounted for almost 10% of mash solids. The complex dissolved during the "protein rest" stage but precipitated among the mash particles during the temperature programmed phase. The level of precipitation was found to depend on mash thickness, malt phenols, oxidation/reduction status, calcium content of the mash liquor and on mash temperature. This precipitate impedes wort run-off and may account for the unpredictability of lautering performance.
Keywords: brewing lautering malt mashing protein precipitation