Solubilisation and Degradation of Wheat Gluten Proteins by Barley Malt Proteolytic Enzymes

Kristof Brijs,1,3 Filip Delvaux,1,2 Viky Gilis1 and Jan A. Delcour1
1Laboratory of Food Chemistry, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Leuven, Belgium
2Centre for Malting and Brewing Science, Katholieke Universiteit Leuven, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium
3Corresponding author. E-mail: kristof.brijs@agr.kuleuven.ac.be

J. Inst. Brew. 108(3), 348-354, 2002   |   VIEW ARTICLE

ABSTRACT
Solubilisation and degradation of wheat gluten proteins by barley malt proteolytic enzymes (BMPE) was investigated with a model buffer system at pH 4.0 and pH 5.6, representing optimal pH for proteolysis and a pH value typical for beer brewing conditions respectively. Under the experimental conditions, incubation of commercial wheat gluten with BMPE solubilised 70% and 20% of the gluten proteins at pH 4.0 and pH 5.6 respectively. Gel permeation chromatography profiles and SDS-PAGE showed that wheat gluten proteins were more degraded by BMPE at pH 4.0 than at pH 5.6. In a laboratory scale barley malt brewing experiment, proteins of worts, prepared with and without wheat gluten, were characterised. Results comparable to those in the model buffer system at pH 5.6 were obtained, which indicated that BMPE indeed solubilise wheat gluten during mashing, but that further degradation is rather limited under these conditions.

Key words:
Barley proteolytic enzymes, vital wheat gluten, wheat beer.

Publication no. G-2002-0826-075  ^©2002 The Institute & Guild of Brewing