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Title: Role of selected oxidative yeasts and bacteria in cucumber secondary fermentation associated with spoilage of the fermented fruit

item FRANCO, WENDY - North Carolina State University
item Perez Diaz, Ilenys

Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/27/2012
Publication Date: 9/15/2012
Citation: Perez Diaz, I.M., Franco, W. 2012. Role of selected oxidative yeasts and bacteria in cucumber secondary fermentation associated with spoilage of the fermented fruit. Food Microbiology. 32:338-344.

Interpretive Summary: Deterioration of fermented cucumber pickles represents an important economic loss for the pickle industry. In this study, the onset of the spoilage process was correlated with the metabolic activity of selected yeasts and lactic acid bacteria naturally present in the fresh fruits. The new understanding of the initiation of secondary cucumber fermentation guides researchers and processors in the development of monitoring strategies to prevent the establishment of these undesirable microbes in the fermentation tanks and thus reduced incidences of spoilage.

Technical Abstract: Changes during the spoilage of fermented cucumber pickles have been attributed to the metabolism of different yeasts and bacteria. In this study six organisms isolated from commercial spoiled cucumber pickles were evaluated for their possible role in primary and secondary cucumber fermentations. The ability of the yeasts Issatchenkia occidentalis and Pichia manshurica to utilize lactic and acetic acids during aerobic metabolism was confirmed and associated with increases in brine pH and the chemical reduction of the fermentation matrix. Lactobacillus buchneri and Pediococcus ethanolidurans were able to produce lactic acid from sugars, but only L. buchneri produced acetic acid at the expense of lactic acid under both aerobic and anaerobic conditions regardless of the initial acidic pH of 3.2 in the medium. The formation of secondary products was associated with the metabolism of Clostridium bifermentans and Enterobacter cloacae, which metabolic activity was observed at medium pH above 4.5. Individually, the selected spoilage microorganisms were found to be able to produce changes associated with secondary cucumber fermentations. The fact that oxidative yeasts and L. buchneri were able to produce chemical changes associated with the initiation of the spoilage process indicates that prevention of the secondary fermentation could be achieved by inhibiting these organisms.