Effect of Abscisic Acid Analogs on Extract Yield, α-Amylase, and Diastatic Power During Malting of Barley. Yueshu Li and Mustafa Rehmanji, Prairie Malt Ltd., Biggar, Saskatchewan, Canada, S0K 0M0, Suzanne R. Abrams, Plant Biotechnology Institute, National Research Council, Saskatoon, Canada, and Lawrence V. Gusta, Crop Development Centre, University of Saskatchewan, Saskatoon, Canada. J. Am. Soc. Brew. Chem. 49:0135, 1991.

Gibberellic acid (GA₃) stimulates the germination and malting of barley (Hordeum vulgare L.) but may impart undesirable characteristics to the malt. Three analogs of abscisic acid (PBI-10, PBI-11, and PBI-16), which also stimulate barley germination, were compared with GA₃ for their effects on malting. Each compound was applied to Harrington barley at a concentration of 10^-5 M at steep-out. GA₃ increased extract yield and enhanced α-amylase activity and diastatic power but resulted in an undesirably higher ratio of soluble protein to total protein (S:T) and darker wort color. Abscisic acid had no effect on extract yield; however, it produced a lower S-T ratio than did the control and reduced α-amylase activity and diastatic power over the germination period. PBI-10 increased extract yield, resulting in an acceptable S-T ratio and wort color. Samples treated with PBI-10, PBI-11, and PBI-16 displayed GA₃-like activity in the first 48 hr by enhancing α-amylase and diastatic power. Addition of the three analogs also promoted the modification process and shortened the conversion time.

Keywords: Abscisic acid analogs, Barley malt, Extract, α-Amylase