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Microbial dynamic and growth potential of selected pathogens in Ethiopian traditional fermented beverages
Annals of Microbiology ( IF 3.0 ) Pub Date : 2021-05-28 , DOI: 10.1186/s13213-021-01635-7
Reda Nemo , Ketema Bacha

The patterns of microbial succession and the associated physicochemical changes in the course of beverage fermentation determine the safety status of the final product against foodborne pathogens. In this study, the microbial dynamics during fermentation of three Ethiopian traditional fermented beverages (namely, borde, tej, and grawa) and the growth potential of selected foodborne pathogens in ready-to-consume beverages were assessed. The raw materials used for lab-scale fermentation of the beverages were bought from open markets of Jimma and Anfilo towns. During fermentation, samples were drawn every 6 h (borde fermentation) and 12 h (grawa and tej fermentation). The dominant microbes of the fermentation phases were determined following standard microbiological methods. The growth potential of Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, Listeria monocytogenes, and Candida albicans in the ready-to-consume beverages were assessed by microbial enumeration over defined storage period. Early fermentation period of all beverages was dominated by aerobic mesophilic bacteria, staphylococci, and Enterobacteriaceae with highest mean counts (Log CFU/ml) of 6.42 ± 0.10, 5.44 ± 0.08, and 5.40 ± 0.11, respectively. At the end of fermentation, yeast counts (Log CFU/ml) dominated in tej (9.41 ± 0.06) and grawa (7.88 ± 0.02) samples, while lactic acid bacteria dominated in borde sample (7.33 ± 0.07). During fermentation, pH dropped for borde (4.58 ± 0.03 to 4.22 ± 0.01), and grawa (4.18 ± 0.10 to 3.62 ± 0.02), but increased for tej (5.26 ± 0.01 to 5.50 ± 0.03) during the first 24 h, though it dropped later down to 3.81 ± 0.02 at 144th h. All reference pathogens were unable to reach infective dose in grawa and tej samples. However, borde sample supported their growth to infective dose within 24 h. Thus, grawa and tej beverages had the capability of inhibiting growth of pathogens while borde needs basic safety control measures during preparation and storage. With further safety evaluation of the products, the production processes of the three beverages could be scaled up for commercial purposes using defined starter cultures originated from the same beverages. However, the safety status of borde calls for further evaluation for alternative shelf-life extension mechanisms including the introduction of organic preservatives from local products such as medicinal plants.

中文翻译:

埃塞俄比亚传统发酵饮料中选定病原体的微生物动态和生长潜力

饮料发酵过程中微生物的演替模式和相关的物理化学变化决定了最终产品对食源性病原体的安全状态。在这项研究中,评估了三种埃塞俄比亚传统发酵饮料(即 borde、tej 和 grawa)发酵过程中的微生物动态以及即食饮料中选定的食源性病原体的生长潜力。用于饮料实验室规模发酵的原材料购自 Jimma 和 Anfilo 镇的公开市场。在发酵过程中,每 6 小时(borde 发酵)和 12 小时(grawa 和 tej 发酵)抽取样品。按照标准微生物学方法确定发酵阶段的主要微生物。大肠杆菌、鼠伤寒沙门氏菌的生长潜力,即食饮料中的金黄色葡萄球菌、单核细胞增生李斯特菌和白色念珠菌在规定的储存期内通过微生物计数进行评估。所有饮料的早期发酵期以需氧嗜温菌、葡萄球菌和肠杆菌科为主,平均计数(Log CFU/ml)分别为 6.42 ± 0.10、5.44 ± 0.08 和 5.40 ± 0.11。在发酵结束时,酵母计数 (Log CFU/ml) 在 tej (9.41 ± 0.06) 和 grawa (7.88 ± 0.02) 样品中占主导地位,而乳酸菌在 ​​borde 样品中占主导地位 (7.33 ± 0.07)。在发酵过程中,波尔德 (4.58 ± 0.03 至 4.22 ± 0.01) 和格拉瓦 (4.18 ± 0.10 至 3.62 ± 0.02) 的 pH 值下降,但 tej (5.26 ± 0.01 至 5.50 ± 0.03) 的 pH 值在第一个 2 小时内升高后来在第 144 小时下降到 3.81 ± 0.02。所有参考病原体均无法在grawa和tej样品中达到感染剂量。然而,borde 样品支持它们在 24 小时内生长到感染剂量。因此,grawa 和 tej 饮料具有抑制病原体生长的能力,而 borde 在制备和储存过程中需要基本的安全控制措施。随着对产品的进一步安全评估,这三种饮料的生产过程可以扩大用于商业目的,使用源自相同饮料的定义的发酵剂培养物。然而,borde 的安全状况需要进一步评估替代保质期延长机制,包括从药用植物等当地产品中引入有机防腐剂。borde 样品支持它们在 24 小时内生长到感染剂量。因此,grawa 和 tej 饮料具有抑制病原体生长的能力,而 borde 在制备和储存过程中需要基本的安全控制措施。随着对产品的进一步安全评估,这三种饮料的生产过程可以扩大用于商业目的,使用源自相同饮料的定义的发酵剂培养物。然而,borde 的安全状况需要进一步评估替代保质期延长机制,包括从药用植物等当地产品中引入有机防腐剂。borde 样品支持它们在 24 小时内生长到感染剂量。因此,grawa 和 tej 饮料具有抑制病原体生长的能力,而 borde 在制备和储存过程中需要基本的安全控制措施。随着对产品的进一步安全评估,这三种饮料的生产过程可以扩大用于商业目的,使用源自相同饮料的定义的发酵剂培养物。然而,borde 的安全状况需要进一步评估替代保质期延长机制,包括从药用植物等当地产品中引入有机防腐剂。随着对产品的进一步安全评估,这三种饮料的生产过程可以扩大用于商业目的,使用源自相同饮料的定义的发酵剂培养物。然而,borde 的安全状况需要进一步评估替代保质期延长机制,包括从药用植物等当地产品中引入有机防腐剂。随着对产品的进一步安全评估,这三种饮料的生产过程可以扩大用于商业目的,使用源自相同饮料的定义的发酵剂培养物。然而,borde 的安全状况需要进一步评估替代保质期延长机制,包括从药用植物等当地产品中引入有机防腐剂。
更新日期:2021-05-28
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