Effect of quality parameters on lipoxygenase activity of wheat malt

Abstract

Wheat malt is one of the main materials used in China's brewing industry, but in previous studies the relationship between the extent of proteolysis (Kolbach index), lipoxygenase (LOX) activity, 2-thiobarbituric acid (TBA) value, and other quality indices of the wheat malts was not sufficiently clear to guide wheat malting. In this study eight wheat malts with different Kolbach indices from the same wheat variety (Triticum aestivum L.) L-2, were prepared. After malting, the LOX activity was found to have decreased by 38.45 to 66.1%. When the Kolbach index was in the range of 31.4-54.2%, LOX activity of the malts increased alongside the increase in the Kolbach index until the Kolbach index was 39.5% then decreased, and there was a significant positive correlation between the Kolbach index and the TBA value: the correlation coefficient was 0.951 (P<0.01). When the Kolbach index was 37.0%, the LOX activity and the TBA value were lower and the other quality indices of the wheat malt were better. The higher TBA value of the wheat malts would relate to the linear increase in the colour of the congress wort. © 2014 Wageningen Academic Publishers.