Contribution of Leuconostocaceae to CO2-mediated bloater defect in cucumber fermentation

Authors: ZHAI, YAWEN - North Carolina State University; Perez Diaz, Ilenys

Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2020
Publication Date: 10/1/2020
Publication URL: https://handle.nal.usda.gov/10113/6916094
Citation: Zhai, Y., Perez Diaz, I.M. 2020. Contribution of Leuconostocaceae to CO2-mediated bloater defect in cucumber fermentation. Food Microbiology. 91:103536. https://doi.org/10.1016/j.fm.2020.103536.
DOI: https://doi.org/10.1016/j.fm.2020.103536

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 Leuconostocaceae family with the defect based on the ability to produce carbon dioxide in cucumber juice and cause bloater defect upon supplementation in a cucumber fermentation. 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 at defining ways to modify the cucumber fermentation cover brines and/or fermentation conditions to reduce the amount of carbon dioxide produced by the Leuconostocaceae and the consequent bloater defect.

Technical Abstract: Fermented cucumber bloater defect, caused by the accumulation of microbiologically produced carbon dioxide, creates significant economic losses for the pickling industry. The ability of Leuconostocaceae, indigenous to cucumber, to grow and produce carbon dioxide during a fermentation and cause bloater defect was evaluated. Leuconostocaceae grew and produced over 40% carbon dioxide in cucumber juice medium, used as a model for cucumber fermentation. The inoculation of Leuconostocaceae to 5 Log CFU/g in cucumber fermentations brined with 25 mM calcium chloride and 6 mM potassium sorbate resulted in no significant differences in bloater defect, colony counts from MRS and VRBG agar plates or the fermentation biochemistry; suggesting an inability of the inoculated bacterial species to prevail in the bioconversion. Acidified cucumbers were subjected to a fermentation inoculated with a Leuconostoc lactis starter culture after raising the pH to 5.9 ± 0.4. Carbon dioxide was produced in the acidified cucumber fermentations to 13.6 ± 3.5% yielding a bloater index of 21.3 ± 6.4; while 8.6 ± 0.8% carbon dioxide and a bloater index of 5.2 ± 5.9 were observed in the non-inoculated control jars. Together the data collected demonstrate that Leuconostocaceae can produce enough carbon dioxide to contribute to bloater defect, if not outcompeted by the leading lactic acid bacteria in a cucumber fermentation.