Effect of storage conditions on post- harvest maturation and maltability of barley

Storage conditions have a major influence on the rate at which dormancy breakdown occurs. The rate of breakdown depends mainly on grain moisture content, storage temperature, storage time and the characteristics of individual batches of barley. Data presented in this paper are a significant addition to the existing knowledge on post harvest maturation of Australian malting barley. Germination of Gairdner and Sloop increased at low moisture content (mc) at storage temperatures above 20oC, as water sensitivity progressively broke down. In contrast, Grimmett germination declined under similar conditions. Stirling was very robust and maintained its germination even under high temperature storage, while Tallon had to be stored below 25oC to prevent loss in barley quality. Samples with high water sensitivity and dormancy were less vulnerable to germination loss. Dormancy and water sensitivity could be overcome by matching storage conditions and barley characteristics. Gairdner, Sloop and Stirling, all samples with some level of dormancy and water sensitivity, showed improved maltability after storage, while Tallon and Grimmett, samples with high pre-storage germination, decreased in maltability under most storage conditions. Longer term storage under mild conditions generally resulted in better malting outcomes. Storage affected Kohlbach index, wort β-glucan, diastatic power and apparent attenuation limit of malt. Changes in germination and maltability need to be considered in combination to develop optimum storage strategies for breaking dormancy and water sensitivity. In dormant grain, enzyme activity of α-amylase and β-glucanase changed with storage, while β-amylase measurements showed no clear trends. Enzyme activity decreased at higher mc and temperatures concurrent with germination loss. Changes in enzyme activity were highly sample-dependent. An understanding of the vulnerability of particular cultivars to damage in storage will assist in increasing and preserving value. Barley with pronounced levels of dormancy and/or water sensitivity can be safely stored at 25° to 30°C for short periods to increase germination. Care must be taken to monitor germination during storage, and moisture content should be kept at or below 12%. Dormant barley stored at low temperatures may not reach malting quality, even over a 12 month period.