S. HUANG (1), J. Yu (1), W. Fan (1), J. Dong (1), H. Yin (1), J. Lu (2), S. Hu (1), J. Liu (1), S. Huang (1);
(1) State Key Laboratory of Biological Fermentation Engineering of Beer, Tsingtao Brewery Co., Ltd., Qingdao, China; (2) School of Biotechnology and Key Laboratory of Industrial Biotechnology, Jiangnan University, Wuxi, China
The kilning process is a key process for final malt quality which is balanced by various positive and negative parameters. In this paper, the influence of kilning conditions on malt quality related to malt lipoxygenase (LOX), malty aroma, flavor stability, and sensory evaluation was investigated using response surface methodology (RSM). Micro-malting (1 kg) trials were conducted with Gairdner barley. A Box-Behnken factorial design with three factors and three levels was used for fitting a second-order response surface. The results indicated that the minimum value (3.36 U/g) of LOX activity was obtained when the kilning temperature, kilning time, and withering time were 90°C, 3.0 h, 14 h respectively, and were especially greatly affected by kilning temperature and withering time. The content of HDMF (4-hydroxy-2, 5-dimethyl-3 (2H)-furanone), TBZ value, and stale flavor aldehydes clearly increased with the rise of kilning temperature and the extension of kilning time and withering time. Second, the corresponding second-order mathematical models were established for predicting each parameter. Among them, P values of model equation of LOX activity, nonenal potential, HDMF, TBZ, methional, and furfural were 0.0303, 0.0301, 0.0402, 0.0037, 0.0103, and 0.0191, respectively, and R2 values were 0.9165, 0.9168, 0.9054, 0.9658, 0.9475, and 0.9317, respectively, which indicated that F examination showed highly significant relativity for regression equations (P < 0.05) and data in excess of 90% could be well explained (R2 > 0.88). Finally, setting the goal of minimizing LOX activity, nonenal potential, TBZ, methional, and furfural and maximizing the content of HDMF, we carried out optimization of the kilning process by balancing the above six positive and negative parameters and the optimum kilning conditions were obtained. The optimum kilning temperature, kilning time, and withering time were 86.56°C, 3.14 h, and 14 h, respectively. These results offer understanding of the influence of kilning conditions on malt quality and provide technological guidance for malting plants.
Shuxia Huang was born in 1977 and obtained her M.Eng. degree from Qilu University of Technology (Jinan, Shandong Province, China) in 2004. She then joined Tsingtao Brewery Co., Ltd. and took up research and development work related to beer brewing. She began her doctoral program at Jiangnan University (Wuxi, Jiangsu Province, China) in 2013. Her research focus is on beer flavor stability, particularly lipid oxidation of malt, and brewing procedures, as well as beer foam stability.