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Abstract：
In this study, the potential use of Pichia fermentans YC5.2 as a starter culture to conduct controlled coffee bean fermentations during on-farm wet processing was investigated. Inoculated fermentations were conducted with or without the addition of 2% (w/v) sucrose, and the resultant microbial growth and metabolism, bean chemistry and beverage quality were compared with spontaneous (control) fermentation. In both inoculated treatments, P. fermentans prevailed over indigenous microbiota and a restricted microbial composition was observed at the end of fermentation process. The inoculation also increased the production of specific volatile aroma compounds (e.g., ethanol, acetaldehyde, ethyl acetate and isoamyl acetate) and decreased the production of lactic acid during the fermentation process. Sucrose supplementation did not significantly interfere with the growth and frequency of P. fermentans YC5.2 inoculum but maintained high levels of wild bacteria population and lactic acid production similar to the spontaneous process. In roasted beans, the content of sugars and organic acids were statistically (p<0.05) similar for all the treatments. However, the inoculated fermentations were shown to influence the volatile fraction of roasted coffee beans by increasing the concentration of yeast-derived metabolites compared to control. Sensory analysis of coffee beverages demonstrated that the use of the YC5.2 strain was favorable for the production of high-quality coffees with distinctive characteristics, e.g., intense perception of \'vanilla\' taste and \'floral\' aromas. In conclusion, the use of P. fermentans YC5.2 in coffee processing was shown to be a viable alternative to control the fermentation step and to ensure consistent quality of finished products.
摘要：
在这项研究中,研究了发酵毕赤酵母YC5.2作为发酵剂在农场湿法加工过程中进行受控咖啡豆发酵的潜在用途。在添加或不添加2％（w/v）蔗糖的情况下进行接种发酵，以及由此产生的微生物生长和代谢，将豆类化学和饮料质量与自发（对照）发酵进行了比较。在两种接种治疗中，发酵菌在本地微生物群中占主导地位，并且在发酵过程结束时观察到有限的微生物组成。接种还增加了特定挥发性芳香化合物的产生(例如，乙醇,乙醛,乙酸乙酯和乙酸异戊酯）并减少发酵过程中乳酸的产生。蔗糖补充没有显着干扰发酵假单胞菌YC5.2接种物的生长和频率，但保持了高水平的野生细菌种群和乳酸产生，类似于自发过程。在烤豆中，所有处理的糖和有机酸含量在统计学上（p<0.05）相似。然而,与对照相比，接种的发酵表明通过增加酵母衍生代谢物的浓度来影响烘烤咖啡豆的挥发性成分。对咖啡饮料的感官分析表明，YC5.2菌株的使用有利于生产具有独特特征的优质咖啡，例如，对“香草”味道和“花香”香气的强烈感知。总之,在咖啡加工中使用发酵假单胞菌YC5.2被证明是控制发酵步骤和确保成品质量一致的可行替代方法。
