Department of Food Technology, Engineering and Nutrition, Chemical Center, Lund University, Box 124, SE-221 00 Lund, Sweden; Instituto de Investigaciones Químicas, Carrera de Ciencias Químicas, Universidad Mayor de San Andrés, 27th Cota Cota, P.O. Box 303, La Paz, Bolivia.
Department of Food Technology, Engineering and Nutrition, Chemical Center, Lund University, Box 124, SE-221 00 Lund, Sweden.
Int J Food Microbiol. 2020 Jul 2;324:108630. doi: 10.1016/j.ijfoodmicro.2020.108630. Epub 2020 Apr 13.
Plant-based beverages are increasing in popularity and quinoa is an attractive option. A hygienic implication linked to the production of beverages from raw material originating from plants is the high microbial contamination. The safety of the product can be guaranteed by lactic acid fermentation, and by using a probiotic strain as starter culture for the fermentation, the final product will benefit from a high number of live probiotics. In this study, a commercial probiotic strain was used for fermentation of a quinoa-based beverage. White quinoa grains were boiled, mixed with water and pasteurized before the beverage was fermented by Lactobacillus plantarum DSM 9843 at 30 °C for 2 days and then stored at 4 °C for 28 days. pH and production of D- and L-lactic acid were monitored, and viable counts were performed for total aerobes, Lactobacillus and Enterobacteriaceae. Colonies from countable plates were randomly picked and in total 335 isolates were identified by 16S rRNA gene sequencing. After heat treatment isolates of Enterobacter, Salmonella, Escherichia, Pantoea, Enterococcus, Klebsiella, and Leclercia were found in the heat-treated but unfermented quinoa beverage. After fermentation pH has decreased below 4, Enterobacteriaceae count was below detection limit and the Lactobacillus count was high 10.6 log CFU/ml (10.3-10.8) (p = 0.002 compared to inoculated counts). During storage pH and the concentration of lactic acid remained stable but after 28 days the lactobacilli count had decreased to 6.9 (6.6-7.2) (p = 0.065 compared to inoculated counts). The majority of isolates picked from Rogosa and Tryptic Soy Agar was identified as Lactobacillus plantarum but 19% and 6% were identified as Enterococcus mudtii and Pediococcus pentosaceous, respectively. The fermentation process applied improved the safety and stability of the product and fortified it with a high content of live probiotics. A safety problem is the spontaneous growth of enterococci (Enterococcus mudtii) during fermentation, enterococci originating from the native quinoa. A solution to this problem can be to increase the rate of the lactic acid fermentation, e.g. by using a higher inoculum of a more active starter culture, and/or to use a starter culture more antagonistic toward enterococci.
植物性饮料越来越受欢迎，藜麦是一个有吸引力的选择。由源自植物的原料生产饮料的一个卫生学问题是微生物污染程度高。通过乳酸发酵可以保证产品的安全性，并且通过使用益生菌菌株作为发酵的起始培养物，最终产品将受益于大量活菌。在这项研究中，使用商业益生菌菌株发酵藜麦基饮料。将白藜麦粒煮沸，与水混合并巴氏杀菌，然后在 30°C 下由植物乳杆菌 DSM 9843 发酵 2 天，然后在 4°C 下储存 28 天。监测 pH 值和 D-和 L-乳酸的产生，并对需氧菌、乳杆菌和肠杆菌科进行活菌计数。从可计数平板上随机挑选菌落，共通过 16S rRNA 基因测序鉴定了 335 个分离株。在热处理后，在热处理但未经发酵的藜麦饮料中发现了肠杆菌、沙门氏菌、大肠杆菌、泛菌、肠球菌、克雷伯氏菌和勒克氏菌的分离株。发酵后 pH 值降至 4 以下，肠杆菌科计数低于检测限，乳酸菌计数很高为 10.6 log CFU/ml（10.3-10.8）（与接种计数相比，p=0.002）。在储存过程中，pH 值和乳酸浓度保持稳定，但 28 天后，乳酸菌计数下降至 6.9（6.6-7.2）（与接种计数相比，p=0.065）。从罗哥萨和胰蛋白胨大豆琼脂中挑选的大多数分离株被鉴定为植物乳杆菌，但分别有 19%和 6%被鉴定为粪肠球菌和戊糖片球菌。应用的发酵工艺提高了产品的安全性和稳定性，并强化了大量活菌。一个安全问题是发酵过程中肠球菌（粪肠球菌）的自发生长，肠球菌源自本地藜麦。解决此问题的方法可以是提高乳酸发酵的速率，例如通过使用更高浓度的更活跃的起始培养物接种，和/或使用对肠球菌更具拮抗作用的起始培养物。
