The objective of this study was to investigate the role of yeasts in the wet fermentation of coffee beans and their contribution to coffee quality using a novel approach. Natamycin (300 ppm) was added to the fermentation mass to suppress yeast growth and their metabolic activities, and the resultant microbial ecology, bean chemistry and sensory quality were analyzed and compared to non-treated spontaneous fermentation we reported previously. The yeast community was dominated by Hanseniaspora uvarum and Pichia kudriavzevii and grew to a maximum population of about 5.5 log CFU/g in the absence of Natamycin, while when Natamycin was added yeasts were suppressed. The major bacterial species in both the spontaneous and yeast-suppressed fermentations included the lactic acid bacteria Leuconostoc mesenteroides and Lactococcus lactis, the acetic acid bacteria Gluconobacter cerinus and Acetobacter persici and the Enterobacteriaceae Enterobacter, Citrobacter and Erwinia. For both fermentations, the mucilage layers were completely degraded by the end of the process and the absence of yeast activities had no significant impact on mucilage degradation. During fermentation, reducing sugars were consumed while lactic acid was accumulated inside the beans, and its concentration was significantly higher in the spontaneous fermentation (3 times) than that where yeasts were suppressed by Natamycin. Glycerol was detected with a concentration of 0.08% in the absence of Natamycin and was not identified when Natamycin was added. Green beans fermented with yeast growth contained a higher amount of isoamyl alcohol (21 times), ethanol (3.7 times), acetaldehyde (8 times), and ethyl acetate (25 times) compared to beans fermented in the absence of yeast activities, which remained higher in the former after roasting. Beans fermented without yeast activities had a mild fruity aroma, and lower sensory scores of fragrances (7.0), flavor (6.5), acidity (6.3), body (7.0) and overall score (6.5) compared to the former. These findings demonstrated the crucial roles of yeasts in wet fermentation of coffee beans and for producing high quality coffee.

这项研究的目的是使用一种新方法研究酵母在咖啡豆的湿发酵中的作用及其对咖啡质量的影响。将纳他霉素（300 ppm）添加到发酵物料中以抑制酵母菌生长及其代谢活性，然后分析由此产生的微生物生态学，豆类化学成分和感官品质，并将其与我们先前报道的未经处理的自发发酵进行比较。酵母菌群主要由Hanseniaspora uvarum和毕赤酵母（Pichia kudriavzevii）所控制，在没有那他霉素的情况下，其最大种群增长至约5.5 log CFU / g，而当加入那他霉素时，酵母菌受到抑制。自发和酵母抑制发酵中的主要细菌种类包括乳酸菌肠膜明串珠和乳酸乳球菌，乙酸菌蜡状葡糖杆菌和醋杆菌属persici和肠杆菌肠杆菌，柠檬酸杆菌和欧文氏菌。对于两种发酵，到过程结束时，粘液层都被完全降解，没有酵母活性对粘液降解没有显着影响。在发酵过程中，还原糖被消耗，而乳酸在豆子内部积累，并且其浓度在自发发酵中的浓度（3倍）明显高于那他霉素抑制酵母的浓度。在不存在纳他霉素的情况下，甘油的浓度为0.08％，添加纳他霉素时未发现甘油。与在没有酵母活性的情况下发酵的豆类相比，经酵母生长发酵的青豆包含较高量的异戊醇（21倍），乙醇（3.7倍），乙醛（8倍）和乙酸乙酯（25倍）。烘烤后前者较高。与前者相比，未经酵母发酵的豆具有淡淡的水果香气，香气（7.0），风味（6.5），酸度（6.3），酒体（7.0）和总分（6.5）的感官评分较低。这些发现证明了酵母在咖啡豆的湿发酵和生产高质量咖啡中的关键作用。