TOTAL AND INDIVIDUAL BARLEY (1–3), (1–4)-β-D-GLUCANASE ACTIVITIES IN SOME GREEN AND KILNED MALTS

Total β-glucanase activity was measured in extracts of malts prepared from three winter and three spring cultivars of barley. Samples were taken at intervals during modification and, after 116 hr, from malt kilned to 65°C. Good malting varieties showed highest levels of total β-glucanase activity, with a high correlation (r = 0.926) with HWE. Angora had the highest activity in the intermediate stages of malting, least loss of activity after heating extracts to 48°C for 10 mins and least loss of activity on kilning. Separation of isozymes by HPLC⁹ confirmed the greater heat stability of isozyme II, but, unlike previous studies on Australian cultivars, we found considerable activity of isozyme I after kilning, even up to 85°C. However, total β-glucanase activity was destroyed by heating extracts of all varieties to 60°C. Angora showed the highest proportion of total activity as isozyme II after kilining. Cultivar differences suggested some scope for breeding varieties with increased total activity by combining high activities of each isozyme. The high correlation of total activity with HWE suggests β-glucanase activity as a rapid test of malting quality.