Factors influencing the rate of modification of barleys during malting

Abstract

The modification of samples of 41 different barley varieties was assessed by staining with Calcofluor following steeping and 48 h of germination. Endosperm modification at this stage varied from 10·3 to 56·2 %. Modification was related significantly to α-amylase and especially β-glucanase levels in the partly malted barley but not to grain size or protein content. Variation in β-glucanase levels explained half the observed variation in modification. However, α-amylase and β-glucanase levels were closely correlated (r = 0·93). High β-glucan barleys modified less completely, a smaller proportion but a higher absolute amount of their β-glucan being degraded. Smallgrained barley produced relatively higher concentrations of hydrolytic enzymes but did not necessarily exhibit greater modification at this stage. The positive correlation of high β-glucanase and low β-glucan content with modification suggested that these factors may determine the rate of modification. However, some samples, especially those with small grains, modified less than would be expected from their β-glucanase and β-glucan contents, suggesting a role for other factors possibly related to endosperm structure.