THE DEVELOPMENT OF β-D-GLUCANASES DURING THE GERMINATION OF BARLEY AND THE EFFECT OF KILNING ON INDIVIDUAL ISOENZYMES†

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Abstract
Two endo-1,3;1,4-β-D-glucanase isoenzymes developed in response to gibberellic acid, during the germination of barley. Two endo-1, 3-β-D-glucanases, one present in ungerminated, steeped grain, also developed but did not appear to be markedly stimulated by the hormone. A comparison of crude and partially purified malt extracts highlighted the errors that are involved in the specific determination of endo-1, 3;1, 4-β-glucanase activity in crude extracts. The development and effect of kilning on individual malt isoenzymes was demonstrated by carboxymethylcellulose (CM-cellulose) chromatography profiles. Kilning and dry-milling of germinated barley caused losses of 80–90% in the specific endo-1,3;1,4-glucanase activity. The effect was less pronounced if wet-milling was substituted for dry-milling. Extraction studies and CM-cellulose chromatography profiles indicated that both endo-1,3;1, 4-β-glucanase isoenzymes were heat labile and were particularly susceptible to oxidation. In contrast, endo-1,3-β-glucanase activity and cellobiase activity in malt extracts were less affected by the kilning process or extraction procedures. Preliminary results suggested that one of the endo-1,3-β-glucanase isoenzymes was more sensitive to kilning.