J. Dong (1), S. HU (1), J. Yu (1), H. Yin (1), S. Huang (1), J. Liu (1), S. Huang (1); (1) State Key Laboratory of Biological Fermentation Engineering of Beer, Tsingtao Brewery Co. Ltd., Qingdao, China

Poster

The hydrolysis of malt starch could be hindered by the cell wall polysaccharide and protein. In this paper, the effects of glucanase, xylanase individually and in combination, as well as proteinase on starch degradation during the course of small-scale, emulated commercial mashing were investigated. Gairdner was mashed and assayed at five time points during mashing for levels of alpha-amylase, beta-amylase, and limit dextrinase and soluble starch content in the supernatant of mash with the addition of barley glucanase (Megazyme), xylanase (Shearzyme 500L, Novozyme), glucanase-xylanase mixture (Ultraflo Max, Novozyme), proteinase (Neutrase 0.8L, Novozyme) or no addition. Compared to the control, the activities of alpha-amylase, beta-amylase, and limit dextrinase were improved to different extents when individual glucanase, proteinase, or glucanase-xylanase mixtures were added to the mash. The greatest increase was found in the activities of beta-amylase and limit dextrinase with the addition of proteinase during mashing. These results indicated that lots of inactive limit dextrinase and beta-amylase forms, which were inhibited by proteinaceous inhibitor, existed in the mash and were released by proteinase. Moreover, the pattern of soluble starch content in the supernatant of mash during mashing showed that the soluble starch content was improved to different extents between 5 and 55 min because of the accelerated release of starch by cell wall hydrolysis. Then, the soluble starch contents were decreased at 115 min with the addition of four enzymes, because there were more starch-degrading enzymes in the mash, especially with addition of proteinase. Finally, the wort sugar content was greatly increased because of the accelerated release of starch and starch-degrading enzymes. Fermentable sugars were improved greatly by proteinase because of high level of limit dextrinase in the mash. Compared to the individual glucanase and xylanase, the glucanase-xylanase mixture had a greater impact on the starch-degrading enzymes and wort sugars, suggesting the access of glucanase to the cell wall was hindered by the xylan. These results offered a comprehensive understanding of the correlation between cell wall-derived polysaccharides, protein, and starch during mashing.

Shumin Hu, born in 1984, received a Ph.D. degree in fermentation engineering from Shandong University in Jinan, China. She joined in the State Key Laboratory of Biological Fermentation Engineering of Beer, Tsingtao Brewery in 2011 as a post-doctoral researcher, working in barley starch degradation.