USDA-ARS, SAA Food Science Research Unit, North Carolina State University, Raleigh, NC 27695-7624, USA.
J Food Sci. 2013 Mar;78(3):M470-6. doi: 10.1111/1750-3841.12057.
Commercial cucumber fermentations are typically carried out in 40000 L fermentation tanks. A secondary fermentation can occur after sugars are consumed that results in the formation of acetic, propionic, and butyric acids, concomitantly with the loss of lactic acid and an increase in pH. Spoilage fermentations can result in significant economic loss for industrial producers. The microbiota that result in spoilage remain incompletely defined. Previous studies have implicated yeasts, lactic acid bacteria, enterobacteriaceae, and Clostridia as having a role in spoilage fermentations. We report that Propionibacterium and Pectinatus isolates from cucumber fermentation spoilage converted lactic acid to propionic acid, increasing pH. The analysis of 16S rDNA cloning libraries confirmed and expanded the knowledge gained from previous studies using classical microbiological methods. Our data show that Gram-negative anaerobic bacteria supersede Gram-positive Fermincutes species after the pH rises from around 3.2 to pH 5, and propionic and butyric acids are produced. Characterization of the spoilage microbiota is an important first step in efforts to prevent cucumber fermentation spoilage.
An understanding of the microorganisms that cause commercial cucumber fermentation spoilage may aid in developing methods to prevent the spoilage from occurring.
商业黄瓜发酵通常在 40000 升发酵罐中进行。在糖消耗后会发生二次发酵，导致形成乙酸、丙酸和丁酸，同时乳酸减少，pH 值增加。变质发酵会给工业生产者造成重大经济损失。导致变质的微生物群仍不完全确定。先前的研究表明，酵母、乳酸菌、肠杆菌科和梭菌在变质发酵中起作用。我们报告说，来自黄瓜发酵变质的丙酸杆菌和果胶杆菌分离物将乳酸转化为丙酸，从而增加 pH 值。16S rDNA 克隆文库的分析证实并扩展了使用经典微生物学方法获得的知识。我们的数据表明，革兰氏阴性厌氧菌在 pH 值从约 3.2 上升到 pH 5 后取代革兰氏阳性Firmicutes 物种，并且产生丙酸和丁酸。变质微生物群的特征是防止黄瓜发酵变质的重要第一步。
了解导致商业黄瓜发酵变质的微生物可能有助于开发防止变质发生的方法。
