Study On The Kinetics Of Barley Amylase And Their Relationship With Malt Quality During Germination

The barley malt is the main raw material of beer brewing. The taste, flavor, nutrition and other qualities of beer are affected by malt qualities. Because the foreign barley has good malt quality and is fit to beer brewing, most domestic beer breweries and malthouses prefer to the imported malting barley, which results in fluctuation of the domestic barley production. Alpha-amylase and beta-amylase are the two most important enzymes to degrade the starch during germination. This research was carried out to determine the kinetics of barley amylase and their relationships with malt qualities during germination by using four domestic barley varieties Xiumai3, Dan2, Gangpi1 and Ganpi4 and two foreign varieties Harrington and Sloop. The main results were as follows:1. The kinetics of theα- amylase during malting barley germinationThe result of ANOVA analysis showed that the kinetics ofα-amylase activity was very significantly different between varieties and between different germination periods. Theα-amylase in Harrington had significant difference with one in other five varieties. Theα-amylase appeared after germination. On the first day, theα-amylase activity in domestic varieties developed more quickly than that in foreign varieties, but the activity ofα-amylase in foreign barley varieties increased quickly, and the level of activity was high than one in the domestic variety after two days'germination. On the third day, theα-amylase activity in all tested barley developed slowly. Theα-amylase activity in Sloop variety declined during the third day of germination, then increased, while the activity of others varieties increased during the whole germination. At the end of germination, there was a great difference inα-amylase activity between different varieties. The level ofα-amylase activity ranged from 737.97 U/g for Gangpi1 to 1355.39 U/g for Harrington in the final malt. The test result of the hypothesis from regression coefficients also showed that the difference ofα-amylase between varieties was significant. The average growth rate of Harrington, which had very significant difference with one in other varieties,was the biggest,and one of Sloop was the second.2. The kinetics of theβ- amylase during malting barley germinationThe result of ANOVA analysis showed that the kinetics ofβ-amylase was very significantly different between varieties and between different germination periods. Dan 2 and Ganpi4 developed quickly on the first day, while Xiumai 3, Sloop and Harrington developed on the second day. Gangpi4 had a stable development model. Meanwhile, the activity level ofβ-amylase in four domestic varieties increased during the whole germination. After germination, the level ofβ-amylase activity during germination was quite different. Theβ-amylase activity was ranged from 685.72 U/g for Xiumai 3 to 1265.65 U/g for Harrington. Analysis of covariance showed that the difference ofβ-amylase activity in all varieties was significant. The test result of the hypothesis from regression coefficients also showed that the difference ofβ-amylase between varieties was significant. The average growth rate of Harrington, which had very significant difference with one in other 4 varieties except Gangpi 4 ,was the biggest, and one of Gangpi 4 was the second.3. The difference of malt qualities and their relationship with amylasesThe result of ANOVA analysis showed that all the malt qualities had significant differences between varieties. The result of multiple comparison showed the malt extract,α- amino nitrogen and kolbach index of Harrington were significantly higher than ones in other varieties, while the malt viscosity of Harrington was significantly lower than that in other varieties. The malt protein content in Harrington was also lower than one in other varieties except Sloop, but the both difference was no significant. The diastatic power of Ganpi4 was significantly higher than other varieties. Xiumai3 has the highest malt viscosity, while the malt extract,α- amino nitrogen, kolbach index and diastatic power were all significantly lower than those in other varieties. The result of correlation analysis showed that both the activities of theα-amylase andβ-amylase had positive correlation with the malt extract,α- amino nitrogen and kolbach index. But those activities had negative correlation with malt viscosity and malt protein content. The dastatic power only had positive correlation withβ-amylase and had no significant correlation withα-amylase.