Study On Wort Turbid Substances Of Jiangsu Barley Malt

Malting barley malt is the main raw material for beer brewing, and malt quality willaffect the quality of the beer directly. Too high turbidity of the wort would affect the filtrationrate adversely, and increase the production cost of the breweries. At the same time, if theturbid substances can’t be removed by boiling effectively, they may affect yeast activityduring the fermentation stage. In order to find out the factors that might increase the turbidityof malt produced from some barley cultivars grown in Jiangsu province, turbid substancesthat might increase the wort turbidity were studied, and the key substances were determined.Additives which can decrease the wort turbidity were screened and compounded. β-amylaseactivity regulation in malting process of Jiangsu malting barley was used to decrease wortturbidity.Turbid substances from Daner, KA4B and Supi6#wort were studied, and resultsindicated that polysaccharides were the most abundant portion in wort turbid substances,followed by proteins. Ion exchange chromatography was used to study the polysaccharides,and results showed that the most abundant hydrolyzed monosaccharide was glucose. Glucosecontents in wort turbid substances of Daner, KA4B and Supi6#were76.60%,69.65%and59.33%, respectively. Other monosaccharides contents were5.45%,6.37%and6.14%,respectively. Gel filtration chromatography was used to investigate the molecular weight ofthe polysaccharides, and results revealed that the molecular weight of the polysaccharidesmainly distributed in1~1.5kDa. Infrared spectroscopy was used to study the structure of thepolysaccharides, and results demonstrated that the chemical bonds which link glucose units inpolysaccharides were mainly α glucosidic bond. In view of these facts, small moleculardextrin which molecular weight were1~1.5kDa was the key substances increasing the wortturbidity of Jiangsu malt.Two dimension difference gel electrophoresis was used to compare expression quantityof the hydrolases probably related to wort turbid substances degradation between KA4B andMetcalfe malt. Results showed that expression quantities of α-amylase1, β-amylase,exo-β-D-glucanase I and arabinofuranosidase I were lower in KA4B malt. Additives whichcan decrease the wort turbidity were screened, and results showed that β-amylase and ascorbicacid can decrease wort turbidity obviously. Beer complex enzymes can increase wort filtrationrate evidently. Box-Behnken response surface method was used to optimize the formula of theadditives.β-amylase activities of Supi6#and Metcalfe barley were compared during the maltingprocess. Results showed that in barleys, β-amylase activities were almost the same. β-amylaseactivities differed gradually between two green malts during malting process. β-amylaseactivity regulation was used to decrease wort turbidity in malting process of Jiangsu maltingbarley. β-amylase was added in germination stage of Supi6#barley. When the β-amylasedosage was200U g-1barley, wort turbidity decreased from7.80EBC to4.96EBC. On thisbasis50mg L-1steeping water CaCl2was added in steeping water, and wort turbiditydecreased to3.49EBC.