Martinez Silvia Juliana, Bressani Ana Paula Pereira, Dias Disney Ribeiro, Simão João Batista Pavesi, Schwan Rosane Freitas
Department of Biology, Federal University of Lavras, Lavras, Brazil.
Department of Food Science, Federal University of Lavras, Lavras, Brazil.
Front Microbiol. 2019 Jun 26;10:1287. doi: 10.3389/fmicb.2019.01287. eCollection 2019.
Coffee quality has recently become a high demand of coffee consumers, due to all the specialty coffees available on the market. Specialty coffees can be generated by favoring growth of some groups of microorganisms during fermentation or by using starters. Just as yeast, a variety of bacteria can be used to generate important flavor precursors. The aim of this work was to test the efficiency of coffee sterilization and adhesion of microbial cells on beans, to evaluate the effect of yeast and bacterial starters on the production of organic and volatile compounds, and selection of potential flavor marker precursors during the wet fermentation. Three yeast and six bacterial starters were inoculated in coffee beans. Coffee sterilization and microbial adhesion was observed by scanning electron microscopy (SEM). Organic compounds were detected by high performance liquid chromatography (HPLC) and volatile compounds by gas chromatography-mass spectrometry (GC-MS). Micrographs from the SEM showed that sterilization was efficient, because there were no microbial cells after autoclaving for 5 min. Also, it was observed an increase of microbial cells from 0 to 48 h of fermentation. Malic, lactic, and acetic acid were only detected in the bacterial treatments. Volatile compounds: 4-ethenyl-1,2-dimethoxybenzene, heptadecanol, 4-hydroxy-2-methylacetophenone, and 1-butanol,2-methyl were only found in yeast treatments. Guaiacol was only produced by the inoculated starters. In conclusion, yeast starters were better producers of volatile alcohols and bacterial starters of acid compounds. This study allowed the selection of potential flavor marker precursors, such as heptadecanol, 4-hydroxy-2-methylacetophenone, 7-methyl-4-octanol, and guaiacol.
由于市场上有各种各样的特色咖啡，咖啡品质最近已成为咖啡消费者的高要求。特色咖啡可以通过在发酵过程中促进某些微生物群体的生长或使用发酵剂来产生。正如酵母一样，多种细菌可用于产生重要的风味前体。这项工作的目的是测试咖啡杀菌效率和微生物细胞在咖啡豆上的附着力，评估酵母和细菌发酵剂对有机化合物和挥发性化合物产生的影响，以及在湿法发酵过程中潜在风味标记前体的选择。将三种酵母和六种细菌发酵剂接种到咖啡豆中。通过扫描电子显微镜（SEM）观察咖啡杀菌和微生物附着力。通过高效液相色谱（HPLC）检测有机化合物，通过气相色谱 - 质谱联用（GC - MS）检测挥发性化合物。SEM的显微照片显示杀菌是有效的，因为高压灭菌5分钟后没有微生物细胞。此外，观察到发酵0至48小时微生物细胞数量增加。仅在细菌处理中检测到苹果酸、乳酸和乙酸。挥发性化合物：4 - 乙烯基 - 1,2 - 二甲氧基苯、十七烷醇、4 - 羟基 - 2 - 甲基苯乙酮和2 - 甲基 - 1 - 丁醇仅在酵母处理中发现。愈创木酚仅由接种的发酵剂产生。总之，酵母发酵剂是挥发性醇的更好生产者，而细菌发酵剂是酸性化合物的更好生产者。这项研究允许选择潜在的风味标记前体，如十七烷醇、4 - 羟基 - 2 - 甲基苯乙酮、7 - 甲基 - 4 - 辛醇和愈创木酚。
