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

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.

► Oxidative yeasts were found able to utilize the lactic and acetic acids present in FCJM. ► Yeast's metabolic activity led to increase pH and the chemical reduction of the medium. ► Lactic acid utilization by Lactobacillus buchneri resulted in acetic acid production. ► Clostridium bifermentans produced butyric acid at medium pH > 5.0. ► Enterobacter cloacae produced propionic acid at medium pH > 5.0.