Variation of Grain and Malt Qualities in Barley as Affected by Cultivars and Environments

Inferior and unstable quality of malt barley in China has limited its wide use in malting and brewing industries. In this research, eight two-rowed barley cultivars were planted at 7 locations with different ecological conditions in southern China, to investigate the cultivar and environmental effect on grain and malt qualities. The results showed that grain protein content differed dramatically among locations, but there were no significant differences among cultivars. For four malt qualities including diastatic power, wort viscosity, Kolbach index and malt extract, significant differences were found among cultivars and locations, except for diastatic power among cultivars. Coefficients of variance(CV)caused by location were greater than those caused by cultivar for each quality parameter, especially for diastatic power and Kolbach index, indicating the predominant influence of environment on malt quality. The analysis showed that grain protein content was positively related to diastatic power and wort viscosity, and negatively to malt extract. Kolbach index was positively related to malt extract, and negatively to diastatic power and wort viscosity. Diastatic power showed positive and negative correlation with wort viscosity and malt extract, respectively.

Genotypic and environmental variation in barley limit dextrinase activity and its relation to malt quality

Variation in the limit dextrinase activity of barley malt, and the relationships between limit dextrinase activity and malt quality parameters were investigated using eight cultivars grown at seven diverse locations in China for two successive years. Limit dextrinase activity varied with genotype and location, with the levels ranging from 0.245 U/g to 0.980 U/g. The results showed that the variation in limit dextrinase activity was more attributable to the environment (location and year) than to the genotype. The response of limit dextrinase activity to the environment differed markedly among cultivars, and was reflected by large difference in coefficient of variation of cultivars across diverse locations. Regression analysis showed that limit dextrinase activity was negatively correlated with malt viscosity (r=?0.52, P<0.01), positively correlated with Kolbach index (r=0.38, P<0.01) and malt extract (r=0.30, P<0.05), but had no significant correlation with malt protein content and diastatic power.

Cultivar and Environmental Effects on p-glucanase Activity in Both Barley Grain and Malt and Its Function in β-glucan Degradation

Eight two-rowed barley cultivars were grown at seven locations in the southern winter-barley zone of China. Mean grainβ-glucanase activity ranged from 39.89 U kg-1 for Suyin2 to 49.75 U kg-1 for Xi-umai3 in 8 cultivars grown at 7 locations, and from 38. 74 U kg-1 in Zhengzhou to 57. 96 U kg-1 in Putian among 7 locations on an average of all cultivars. Correspondingly, mean malt β-glucanase activity of 8 cultivars ranged from 313.33 U kg-1 for ZAU3 to 489. 89 U kg-1 for Daner Barley, and of 7 locations from 330.40 U kg-1 in Yancheng to 418. 24 U kg-1 in Putian. There were significant differences among cultivars and locations in maltβ-glucanase activities. The locations showed much larger variation in maltβ-glucanase activities than cultivars. The reduction of total β-glucan content after malting varied in both cultivars and locations, with a mean of 78.31%. The analysis of correlations showed that maltβ-glucan content was significantly positively and negatively correlated with grain β-glucan content and malt β-glucanase activity, respectively, and malt β-glucanase activity was significantly positively correlated with grain β-glucanase activity.

The influence of drought stress on malt quality traits of the wild and cultivated barleys

As a major abiotic stress,drought causes instability and deterioration of malt barley quality.There is distinct difference among barley cultivars in the responses of the main malt quality traits to drought stress.In the previous study,we identified some Tibetan wild barley accessions with relatively less change of malt quality traits under drought.In this study,we examined the impact of drought stress during grain filling stage on grain weight and several important malt quality traits,including total protein content,β-glucan content,limit dextrinase activity,β-amylase activity,and protein fractions in four barley genotypes(two Tibetan wild accessions and two cultivars).Drought treatment reduced grain weight,β-glucan content,and increased total protein content,β-amylase activity.These changes differed among barley genotypes and treatments,and are closely associated with grain filling process and kernel weight.All the results indicated Tibetan wild barley had great potential for developing drought tolerant barley cultivars.Relatively stable kernel weight or filling process under water stress should be highlighted in malt barley breeding in order to reduce the effect of water stress on malt barley quality.

Genotypic and Environmental Variations of Arabinoxylan Content and Endoxylanase Activity in Barley Grains

Arabinoxylan （AX） content in barley grains is an important quality determinant when barley is used as raw material of malt or beer production. The cultivar and environmental variations of total arabinoxylan （TAX）, water extractable arabinoxylan （WEAX） and endoxylanase activity （EA） were investigated using eight barley cultivars growing at seven locations with diverse environmental conditions. The results showed that both barley cultivar and location significantly affected the TAX, WEAX and EA levels, but the variations of TAX content and EA were mainly attributed to cultivar, while the impact of location on WEAX content was greater than that of cultivar. Correlation analysis indicated that TAX was significantly correlated to WUAX.