VIEW ARTICLE    DOI: 10.1094/ASBCJ-52-0048

Effect of Abscisic Acid Optical Isomers, Alone or in Combination with Gibberellic Acid, on Barley Malt Quality. Yueshu Li and Mustafa Rehmanji, Prairie Malt Ltd., Biggar, Saskatchewan, S0K 0M0, Canada; Suzanne R. Abrams, Plant Biotechnology Institute, National Research Council of Canada, Saskatoon, Saskatchewan, S7N 0W9, Canada; and Lawrence V. Gusta, Crop Development Centre, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 0W0, Canada. J. Am. Soc. Brew. Chem. 52:0048, 1994.

The effect of racemic abscisic acid (ABA) and the individual optical isomers, (+)ABA and (-)ABA, alone or in combination with gibberellic acid (GA₃), on the malting quality of Bonanza barley was determined. When GA₃ was the sole treatment, it was applied after 0, 6, 12, 18, and 24 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 germination. All chemicals were added at a concentration of 10^-5 M. GA₃ increased extract yield and enhanced α-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 with 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 grind extract, soluble protein, diastatic power, α-amylase, friability, and malting losses. In combination with GA₃, these two treatments reduced the effect of GA₃ on soluble protein and malting losses but still produced a malt with higher fine grind extract, diastatic power, and α-amylase activity than did the controls. These results indicate that (-)ABA and racemic ABA, in combination with GA₃, can produce a desirable malt in a shorter time than can non-GA₃ treated barley.

Keywords: Abscisic acid optical isomers, Barley malt quality, Gibberellic acid