評估二階段醬醪發酵法及最適化初期發酵條件以提高醬油品質

• Main Authors: Nguyen Xuan Hoang, 阮宣宏
• Other Authors: Cheng-Kuang Hsu
• Format: Others
• Language: en_US
• Online Access: http://ndltd.ncl.edu.tw/handle/tssf46

碩士 === 國立嘉義大學 === 食品科學系研究所 === 104 === The traditional soy sauce fermentation method takes a long time to complete (6–12 months), rapid fermentation methods are often needed by the soy sauce industry. In this study, we evaluated a two-stage soy sauce fermentation process and compared the results with traditional fermentation. At the first stage, the koji was mixed with 5% brine solution at 1:2 ratio (w/w) and incubated at 45°C, for 2 days. And then at the second stage, the fermentation temperature was maintained at 30°C either without or with the addition of Zygosaccharomyces rouxii, and the brine contents were increased from 5% to 14, 18, and 22%. As a result, at the first stage, the application of high temperature and low brine content was effective in producing rapid fermentation. Namely biochemical properties, they were found to be particularly increased by 60%, 120% and 130% in the contents of total nitrogen, formal nitrogen and amino nitrogen, respectively, more so than in the control sample fermented outdoors. Whereas pH, reducing sugar and total acid contents were 4.30, 0.63 g/100 ml and 2.58 g/100 ml, respectively, which were significantly different to the control sample corresponding to 6.19, 2.03 g/100 ml and 0.47 g/100 ml, respectively. Regarding microbial properties, the treatment samples showed lower yeast and higher lactic acid bacteria counts after the first stage of fermentation. These significant differences clearly affected the second fermentation stage, especially around 80–100% changes of the tested biochemical indexes taken place in the period only until 14 days. Nevertheless, the results indicated lower sensory properties in rapid fermentation method compared with the control after 4 months fermentation. Moreover, apart from the effects of temperatures, the soy sauce samples produced with the different brine concentrations and either without or with Z. rouxii inoculum were not remarkably different on not only biochemical properties but also sensory ones. Thereafter, the objective of further study was to optimize the process parameters for preparation of first fermentation stage of soy sauce, which was considered as an enzymatic hydrolysis for the further fermentation stage. Temperature (35, 40 and 45°C), fermentation time (1, 3 and 5 days) and brine content (5 and 10% w/w) were studied as independent variables. The responses evaluated for deciding the optimum conditions were biochemical properties of total nitrogen, amino nitrogen, reducing sugar and total acid contents and pH, as well as microbial properties of yeast and total bacterial counts. Experimental data were fitted well into second-order polynomial models. The simultaneously optimal conditions were 40.7°C temperature, 4.6 days fermentation time and 10% w/w brine content. The optimized response values for total nitrogen, amino nitrogen, reducing sugar and total acid contents and pH were 1.43, 0.65, 2.79, and 1.28% and 5.48, respectively. These conditions could obtain total nitrogen (> 1.4%) and amino nitrogen (> 0.56%) contents satisfying the requirement of first-grade soy sauce within 5 days fermentation.