IMPROVED PROCESSES FOR CUCUMBERS, CABBAGE, SWEETPOTATOES, AND PEPPERS TO MAKE HIGH QUALITY, NUTRITIOUS PRODUCTS AND REDUCE POLLUTION
Location: Food Science Research
Title: Characterization of cucumber fermentation spoilage bacteria by enrichment culture and 16S rDNA cloning
Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 2, 2013
Publication Date: March 1, 2013
Citation: Breidt, F., Medina-Pradas, E., Wafa, D., Perez Diaz, I.M., Franco, W., Huang, H., Johanningsmeier, S.D., Kim, J. 2013. Characterization of cucumber fermentation spoilage bacteria by enrichment culture and 16S rDNA cloning. Journal of Food Science. 78(3):M470-M476.
Interpretive Summary: Commercial cucumber fermentation tank spoilage can be an economic problem for the cucumber fermentation industry which supplies the fast food (hamburger dill pickle slices) and retail markets. Recent studies have identified adverse biochemical changes that occur in these large scale (10,000 gallon) tanks, and some of the bacteria that are implicated in the secondary spoilage fermentation have been identified. This report is the first to show the bacteria present using DNA based methods that do not require culturing bacteria. These DNA methods can give a clearer picture of the bacterial ecology than culture based methods. We found that strictly anaerobic organisms are present in the fermentation that are difficult to cultivate, and were not previously identified, including a bacterium closely related to a beer spoilage microorganism. Knowing which bacteria participate in the spoilage fermentation may help with the development of novel technology to prevent secondary spoilage fermentations from occurring, affording significant savings to the pickled vegetable industry.
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 pHrises from around 3.2 to pH5, and propionic and butyric acids are produced. Characterization of the spoilage microbiota is an important first step in efforts to prevent cucumber fermentation spoilage.