| Summary: | 碩士 === 大同大學 === 生物工程研究所碩士在職專班 === 91 === This study investigated the influence of the temperature and aeration on yeast propagation in a large beer brewery. The fermentation temperature （9,10,11℃）and aeration time interval were the control variables to study the optimum conditions for the subsequent yeast propagation tanks YPT-2 and YPT-3. Apparent plato, alcohol, and yeast concentration in the fermentation wort were measured for each experiment.
The results indicated that the higher of incubation temperature the lower of apparent plato, and higher alcohol and yeast concentration of the transferred wort at fixed aeration.
When the temperature was controlled at constant, more aeration resulted higher apparent plato and lower alcohol, however, the yeast concentration was almost the same. It was better to transfer the yeast in the exponential phase for YPT-2 tank, and the yeast concentration had better more than 7.50×107 cells/ml. Moreover, alcohol concentration should not be too high, apparent plato should be in the range of 5~7o P. The optimum conditions for propagation of yeast in the YPT-2 tank were 1 min. aeration in 10 min. interval, and the temperature should be 10℃ or 11℃.
It was better to transfer the wort of YPT-3 in high yeast concentration (more than 7.50×107 cells/ml) to the following fermentation tank. The yeast could ferment wort in anaerobic condition (alcohol fermentation), the apparent plato should be in the range of 4 ~6o P. The optimum conditions for propagation of yeast in the YPT-3 tank were 4 min. aeration in 20 min. interval, and the temperature should be 10℃ or 11℃.
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