Hydrophobic polypeptide extraction during high gravity mashing - Experimental approaches for its improvement

Abstract

The aim was to establish if a substantial increase in hydrophobic polypeptides could be achieved during high gravity mashing. When worts with gravities ranging from 5-20°P were analysed for hydrophobic polypeptide content it was found that there was no appreciable increase in hydrophobic polypeptide levels. Remashing of the spent grains from low and high gravity mashes demonstrated that this resulted from inefficient extraction of hydrophobic polypeptide levels during the mashing process. For example, wort produced from remashed high gravity spent grains contained 150 mg/L hydrophobic polypeptides compared to only 10 mg/L in the low gravity remashed spent grains. Experiments were conducted, employing standard mashing techniques, in an attempt to increase the extraction of hydrophobic polypeptides during high gravity mashing. Thus the use of gypsum, proteolytic stands, varying liquor to grist ratios and wheat malt addition were all investigated for their effect on hydrophobic polypeptide extraction during high and low gravity mashing. Wort analysis demonstrated that none of the techniques employed had a significant effect on hydrophobic polypeptide extraction. When wort from remashed spent grains was used as mashing in liquor for a fresh mash and the resultant worts analysed for hydrophobic polypeptides it was observed that no increase in hydrophobic polypeptide extraction was achieved. For example, wort from the remashed high gravity spent grains, containing 140 mg/L hydrophobic polypeptides, when used as mashing-in liquor, produced no increase in hydrophobic polypeptide levels in the resultant high gravity wort (230 mg/L) when compared to a high gravity wort produced using distilled water as mashing-in liquor (255 mg/L). It is therefore concluded that a saturation point has been reached and no more hydrophobic polypeptides can be extracted during mashing regardless of the procedures employed.