S. HU (1), W. Fan (1), J. Dong (1), H. Yin (1), J. Yu (1), S. Huang (1), S. Huang (1), J. Liu (1);
(1) State Key Laboratory of Biological Fermentation Engineering of Beer, Tsingtao Brewery Co. Ltd., Qingdao, China
Prediction of brewing performance is important and most breweries still resort to a small-scale fermentability test, which entails the fermentation of wort under controlled conditions in an excess amount of yeast. The objective of study was to develop a new simple and quick approach based on osmolyte concentration (OC) to predict wort fermentability. Eight malts from seven barley cultivars were assayed for DP (diastatic power), starch-degrading enzymes (α-amylase, β-amylase, and limit dextrinase). Then malts were mashed to determine wort OC (WOC), RDF (real degree of fermentation), and sugar in a small-scale mashing protocol with a mash temperature of 65°C. First, WOC correlated better with α-amylase and limit dextrinase (r = 0.881 and 0.831, respectively; P < 0.01) than did DP, which only had a correlation with β-amylase (r = 0.855, P < 0.01). Moreover, wort RDF correlated significantly with WOC (r = 0.929, respectively; P < 0.01), suggesting that WOC can be used to evaluate malt fermentability without use of yeast and fermentation step. Meanwhile, WOC correlated dramatically with maltose, glucose, total sugars and fermentable sugars (r = 0.923, 0.928, 0.807, and 0.982, respectively; P < 0.01). These suggested that WOC can be used to quickly predict the wort sugar contents. Furthermore, the effect of mashing temperature and duration on the WOC, RDF, and sugar was discussed. Adjusted mash temperature near 65°C or extended mash duration dramatically increased RDF and WOC simultaneously, whereas ME (malt extract) was relatively stable. Similarly, WOC had significant correlations with RDF and fermentable sugars (r = 0.912 and 0.942, respectively; P < 0.01), suggesting that WOC could provide a simple and fast tool to assist brewers in optimizing mash parameters toward the production of ideal wort fermentability and sugar content. In conclusion, the ability of WOC to predict malt fermentability and sugar content allows brewers to keep better control of fermentability in the face of variation in malt quality and quickly adjust mashing conditions for the consistency of wort fermentability.
Shumin Hu was born in 1984 and received a Ph.D. degree in fermentation engineering from Shandong University in Jinan, China. She joined the State Key Laboratory of Biological Fermentation Engineering of Beer, Co. Ltd. in August 2011 as a post-doctoral researcher. Having finished her postdoctoral career in 2014, she continues to work for Tsingtao Brewery Co. Ltd. and focuses on research on starch degradation, including amylase, malt quality evaluation, process control, and so on.