VARIETAL DIFFERENCES IN BARLEYS AND MALTS: VII. STARCH-LIQUEFYING ACTIVITY, AUTOLYTIC DIASTATIC ACTIVITY AND THEIR CORRELATIONS WITH SACCHARIFYING AND PROTEOLYTIC ACTIVITY

Abstract

Determinations made on 144 samples of malt, representing 12 varieties grown at 12 experimental stations in Canada, show that varietal differences exist with respect to starch liquefying activity (max. 768, min. 275 units) and autolytic diastatic activity (max. 958, min. 664 units). Varieties of poor malting quality tend to be low with respect to both properties. The effect of environment is also considerable (liquefying, max. 510, min. 288; autolytic, max. 806, min. 704).The correlation coefficients among liquefying, autolytic diastatic, saccharifying, and proteolytic activities of malt and total barley saccharifying activity were studied. Significant inter-varietal associations exist between each pair of properties, but partial correlation studies suggest that only those between saccharifying activities of barley and malt (r = 0.90), and between liquefying and autolytic activities of malt (r = 0.97), represent real and close relations. The other associations between pairs of enzymatic activities seem to reflect mainly positive correlations between each activity and total salt-soluble nitrogen in the barleys.Significant intra-varietal associations exist between each pair of enzymatic activities, and between each activity and total barley nitrogen. It appears that environmental factors which tend to increase total nitrogen also tend to increase each enzymatic activity, but these do not increase regularly with respect to each other and are not closely related. Partial correlations independent of total nitrogen suggest that only barley and malt saccharifying activities (r = 0.67) and liquefying and autolytic activities of malt (r = 0.63) are related within varieties.It appears that the rate of autolysis in samples of different varieties from the same station is controlled almost entirely by starch liquefying activity, but the latter property is not the limiting factor controlling autolysis in samples of the same variety from different stations. Within varieties some other factor, presumably starch resistance, must play an important part.