Study On Improving Domestic Malt Quality By Using Microbes

Malt is the major material used for beer brewing and its quantity directly determines the quality of beer. Partial domestic malts have poor filtration performance. Promoting the filtration performance by using Geotrichum candidum was studied in this paper.4 % sterilized milled malt suspension was used as a growth medium and the activities ofβ-glucanase, xylanase, protease and cellulase produced by 40 strains of fungi microbes were studied. The weighted mark method was used to analyze activities of the above enzymes, and four fungi strains including No.3, No.12, No.18 and No.39 were selected as the malting microbial strains. The malting trials indicated that four fungi strains could improve the modification of malt and the effect of G. candidum No.12 was the best. G. candidum No.12 was finally determined as the malting microbial strain. The conditions for spore production of No.12 were studied, and the optimum conditions were the medium was 5 oP wort, the initial pH was 5.5, the spores inoculation concentration was 3%, the volume of medium was 50 mL in 250 mL flask, the shaking speed was 200r/min, the temperature was 30℃and the culture time was 44 h. The spores yield reached 1.0×10~8 cfu/mL。The microorganism-malting technology had been studied with the Jiangsu barley KA-4B which had low germination rate. The optimum micromalting technologies were adding sprout G. candidum spores into the first steeping water, the inoculation concentration was 106/g dry barley. The filtration performance of final malt had been obviously improved, and filtration volume within sixty minutes, increased by 63.4%. The results of wort mashing and beer brewing by using G. candidum malts to partly instead import malts showed that using G. candidum malts have no effects on index of wort, beer fermentation and index of beer. All parameters of beer meet the standard of GB4927-2008。It indicated that the G. candidum malts could instead of 20% import malts for mashing and brewing.Improvement on filtration performance of final malt by G. candidum was preliminary studied. Adding G. candidum during malting process could obviously inhibite the growth of other fungi microbes, and could promote the activities ofβ-glucanase, xylanase, protease and cellulase in green malt. The result of electron microscope scanning showed that G. candidum could be adsorbed to the barley surface on the initial steeping stage. The G. candidum increased rapidly with the germinating process and occupied the most surface of barley at the end of germination. It became the dominant species and inhibited the growth of other fungi microbes...