Ndayambaje Jean Bernard, Nsabimana Antoine, Dushime Sylvie, Ishimwe Florence, Janvier Habinshuti, Ongol Martin P
Department of Chemistry School of Science College of Science and Technology University of Rwanda Kigali Rwanda.
Food Sci Nutr. 2018 Nov 20;7(1):287-292. doi: 10.1002/fsn3.887. eCollection 2019 Jan.
Coffee is a socioeconomic important plant all over the world due to its exportation and how it provides income to the farmers and the country. However, potato taste defect (PTD) affects the Rwandan coffee quality. The smell is reported to be caused by some bacteria that are responsible for the off-flavor and may also be related to the infestation of Antestia pest which are in its elimination process. The aim of this study was to isolate, biochemically characterize, and identify bacteria producing potato flavor from Rwandan coffee. Five samples were obtained from different regions ( and ) of Rwanda. Bacteria were isolated and enumerated in the nutrient agar media followed by culture on nutrient and tryptic soy broth media. Bacteria were also cultured to several carbon sources such as glucose, fructose, sucrose, starch, pectin, and galactose to smell the odor produced by those bacteria. DNA extraction of isolates was done, and the resulting DNA strands were undergone three steps of PCR to be amplified using the forward primer and reverse primer. The identification of bacteria producing potato flavor from Rwandan coffee beans was done through 16S rDNA method followed by sequence analysis using FinchTV software and BLAST. Earthy odor was the mostly produced one for nutrient agar and tryptic soy agar media, and for carbon sources such as sucrose, glucose, pectin, fructose, and galactose. The potato odor was recorded mostly from damaged floaters and hand-sorted damaged coffee beans. However, other odors such as fruity and ferment were found to be produced by bacteria in coffee beans. The study came up by concluding the presence of different kinds of bacteria including and which are responsible for the formation of 2-isopropyl-3-methoxypyrazine (IMP) in coffee beans and cause the production of potato flavor.
由于咖啡的出口以及它为农民和国家带来收入的方式，咖啡在全球都是一种具有社会经济重要性的作物。然而，马铃薯风味缺陷（PTD）会影响卢旺达咖啡的品质。据报道，这种气味是由一些导致异味的细菌引起的，也可能与正在被消灭的咖啡豆象虫害有关。本研究的目的是从卢旺达咖啡中分离、进行生化特性分析并鉴定产生马铃薯风味的细菌。从卢旺达不同地区（此处原文缺失具体地区信息）采集了五个样本。在营养琼脂培养基中分离并计数细菌，随后在营养肉汤和胰蛋白胨大豆肉汤培养基上进行培养。还将细菌接种到几种碳源上，如葡萄糖、果糖、蔗糖、淀粉、果胶和半乳糖，以闻这些细菌产生的气味。对分离出的细菌进行DNA提取，得到的DNA链经过三步PCR反应，使用正向引物和反向引物进行扩增。通过16S rDNA方法对卢旺达咖啡豆中产生马铃薯风味的细菌进行鉴定，随后使用FinchTV软件和BLAST进行序列分析。对于营养琼脂和胰蛋白胨大豆琼脂培养基以及蔗糖、葡萄糖、果胶、果糖和半乳糖等碳源，主要产生土腥味。马铃薯气味大多记录于受损的漂浮物和手工挑选的受损咖啡豆中。然而，发现咖啡豆中的细菌还会产生其他气味，如水果味和发酵味。该研究得出结论，咖啡豆中存在包括（此处原文缺失具体细菌种类信息）在内的不同种类细菌，它们负责在咖啡豆中形成2 - 异丙基 - 3 - 甲氧基吡嗪（IMP）并导致马铃薯风味的产生。
