EFFECT OF ABSCISIC-ACID OPTICAL ISOMERS, ALONE OR IN COMBINATION WITHGIBBERELLIC-ACID, ON BARLEY MALT QUALITY

The effect of racemic abscisic acid (ABA) and the individual optical i somers, (+)ABA and (-)ABA, alone or in combination with gibberellic ac id (GA3), on the malting quality of Bonanza barley was determined. Whe n GA3 was the sole treatment, it was applied after 0, 6, 12, 18, and 2 4 hr of germination. In combination experiments, GA3 was added at 0 hr and the abscisins were added after 0, 6, 12, 18, and 24 hr of germina tion. All chemicals were added at a concentration of 10(-5) M. GA3 inc reased extract yield and enhanced alpha-amylase activity and diastatic power but resulted in an undesirably high soluble protein content and increased malting losses. The optimal time for GA3 addition varied wi th the parameters measured. Natural ABA, the (+) isomer, had little or no effect on any of the parameters and did not inhibit the effect of GA3 on malting. In contrast, (-)ABA and racemic ABA reduced the fine g rind extract, soluble protein, diastatic power, alpha-amylase, friabil ity, and malting losses. In combination with GA3, these two treatments reduced the effect of GA3 on soluble protein and malting losses but s till produced a malt with higher fine grind extract, diastatic power, and alpha-amylase activity than did the controls. These results indica te that (-)ABA and racemic ABA, in combination with GA3, can produce a desirable malt in a shorter time than can non-GA3 treated barley.