The effects of different timing of N fertilizer application at the same rate on grain β-amylase activity, protein con- centration, weight and malt quality of barley were studied. Grain β-amylase activity and protein concentration were significantly higher in treatments where all top-dressed N fertilizer was applied at booting stage only or equally applied at two-leaf stage and booting stage than in the treatment where all top-dressed N fertilizer was applied at two-leaf age stage only. On the other hand, grain weight and malt extract decreased with increased N application at booting stage. There were obvious differences between barley varieties and experimental years in the grain and malt quality response to the timing of N fertilizer application. It was found that grain protein concentration was significantly and positively correlated with β-amylase activity, but significantly and nega- tively correlated with malt extract and Kolbach index. The effect of grain protein concentration on malt quality was predominant over the effect of grain β-amylase activity.
Barley has been in use as food and fodder for thousands of years. and also used currently as the most important raw material in malting and brewing. The quality of malt barley is not much satisfied with the requirement by malting and brewing industry worldwide, although the great effort has been devoted to its improvement through breeding and agronomy. The quality of malt barley is involved in many physical and chemical traits, including hydrolytic enzymes. Of them, kernel protein content, beta-amylase activity, beta-glucan content and kernel plumpness have dramatic influence on malting or brewing quality. The expression of these quality parameters varies greatly in genotypes and is easily changed by diverse environments and agronomic practices. This paper reviewed the important role of various parameters influencing the quality of malt barley and the effect of different factors on them.
