The Potential of Ethylene as an Alternative to GA₃ Treatment during Malting of Barley (Hordeum valgare)

Abstract

Treatment of barley grain with gibberellic acid (GA 3 ) during malting promotes abnormal proteolysis and rapid rootlets growth affecting malt quality. This study investigated the potential of ethylene treatment as an alternative by comparing the amylase activity, total starch and total reducing sugars of germinating 'Puma' barley seeds treated with ethylene, 1-methylcyclopropane (1-MCP), GA 3 , daminozide (B-nine), GA 3 + 1-MCP, ethylene + B-nine and the control after 24, 48 and 72 h from soaking. Ethylene had no effect on amylase activity. B-nine reduced amylase activity by 16 and 9.6% compared to the control after 48 and 72 h, respectively. The amylase activity of ethylene + B-nine treated seeds was higher (13.3 and 4%) than B-nine treated seeds after 48 and 72 h. This suggest that endogenous GA is important for normal amylase activity and, ethylene stimulates amylase activity where GA synthesis is inhibited. Ethylene and GA 3 treatments reduced starch (83.3 mg g -1 and 76.7 mg g -1 , respectively) and increased reducing sugars (16.0 and 17.1 µg ml -1 , respectively) compared to the control (115.3 mg g -1 starch and 12.1 µg ml -1 reducing sugars) after 72 h. It was concluded that, ethylene may replace GA 3 treatment without interfering with starch changing processes during barley malting.