| Summary: | 碩士 === 國立臺灣大學 === 食品科技研究所 === 107 === Recently, many studies have reported that mixed fermentation of Saccharomyces yeast and non-Saccharomyces yeast has an effect on enhancing the content and complexity of wine aroma compared to single strain fermentation. In this study, yeasts were screened from fruit peels to adapt to the wine fermentation environment, and the optimum mix-fermentation conditions for ethyl acetate were studied. The experiment used YPDA medium which added chloramphenicol as a selecting platform, and YPD medium which adjusted pH, glucose concentration and alcohol concentration to mimic wine fermentation condition. Saccharomyces cerevisiae (A5) and Pichia anomala (F8) were selected for RSM (response surface methodology) experiments because of the high ethyl acetate production potential. Sequential inoculation interval time, temperature, and initial sugar concentration was chosen as the RSM factor to obtain the maximum ethyl acetate yield. After the RSM experiment, instrumental analysis and sensory evaluation using 9-Point hedonic scale method was carried out. According to the RSM experiment, the highest ethyl acetate yield of 85.77 ppm can be obtained at a temperature of 21.36oC, an initial sugar concentration of 25.86%, and an interval inoculation time of 32.48 h. Instrumental analysis shows an increase concentration of Ethyl acetate, 1-propanol, Isobutanol, 2-Methyl-1-Butanol, Ethyl octanoate, 2,3-Butanediol, 2-Phenylethanol and Tyrosol in optimized wine compare with un-optimized wine. In sensory evaluation experiment, five kinds of wine including three kinds of commercial wine and two kinds of self-made wine fermented under un-optimized condition and optimized condition was served to the judgers. The result indicates that the wine made under optimized condition was rated higher than the un-optimized wine and two commercial wine in overall liking, flavor, mouthfeel and aftertaste. This study confirms that the optimal mix-fermentation does enhance the aroma concentration of the wine and has a better flavor. It is expected that the research results will provide more applications in the wine industry.
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