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Research Project: Improved Processes for the Preservation and Utilization of Vegetables, Including Cucumber, Sweetpotato, Cabbage, and Peppers to Produce Safe, High Quality Products with Reduced Energy Use and Waste

Location: Food Science Research

Title: CO2-mediated bloater defect can be induced by the uncontrolled growth of Enterobacteriaceae in cucumber fermentation

item ZHAI, YAWEN - North Carolina State University
item Pagan Medina, Christian
item Perez Diaz, Ilenys

Submitted to: Food Science and Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2023
Publication Date: 10/1/2023
Citation: Zhai, Y., Pagan Medina, C.G., Perez Diaz, I.M. 2023. CO2-mediated bloater defect can be induced by the uncontrolled growth of Enterobacteriaceae in cucumber fermentation. Food Science and Nutrition. 11(10):6178-6187.

Interpretive Summary: The industrial fermentation of cucumbers has suffered from bloater defect for decades. This defect can cause up to 20% production losses for pickle processors in the USA. This study aimed at identifying potential root causes of the defect so that prevention and control measures can be implemented. We identified a particular group of bacteria naturally present in cucumbers as a causative agent of the defect and the target for control measures. We are relating the influence of bacteria belonging to the Enterobacteriaceae family with the defect based on their main mode for sugar metabolism, known as respiration, which produces carbon dioxide gas. It is understood that the accumulation of carbon dioxide inside the cucumbers builds pressure against the internal tissue causing its displacement and the formation of a hollow cavity. We aim to find ways to modify the cucumber fermentation cover brines and/or fermentation conditions to reduce the amount of carbon dioxide produced by Enterobacteriaceaea and the consequent bloater defect.

Technical Abstract: Enterobacteriaceae are known to proliferate in cucumber juice, deriving energy from the fermentation of sugars to organic acids and ethanol, and theoretically generating carbon dioxide. We hypothesized that the carbon dioxide produced by the indigenous Enterobacteriaceae in the early stage of cucumber fermentation accumulates in the fermenting fruits causing bloater defect. The ability of seven Enterobacteriaceae, indigenous to cucumber, to grow and produce carbon dioxide in cucumber juice medium (CJM), a sterile model system for cucumber fermentation, was characterized. The induction of bloater defect in cucumber fermentation conducted with pasteurized and acidified fruits was also evaluated. The generation times of the seven Enterobacteriaceae in CJM ranged between 0.25 and 8.20'h and resulted in carbon dioxide production to estimated amounts of 7.22–171.5'mM. Enterobacter cancerogenus and Enterobacter nimipressuralis were among the bacteria that produced the most and the least carbon dioxide in CJM, respectively, at estimated mM concentrations of 171.58'±'42.96 and 16.85'±'6.53. Inoculation of E.'cancerogenus and E.'nimipressuralis in acidified and pasteurized cucumbers resulted in the production of 138 and 27'mM carbon dioxide, respectively. Such Enterobacteriaceae produced 2% hydrogen in the model cucumber fermentations. A bloater index of 25.4 and 17.4 was calculated from the cucumbers fermented by E.'cancerogenus and E.'nimipressuralis, respectively, whereas no defect was observed in the fruits collected from uninoculated control fermentation jars. It is concluded that the metabolic activity of the Enterobacteriaceae indigenous to cucumber can produce sufficient carbon dioxide in cucumber fermentations to induce bloater defect.