Modulation of the bacterial population in commercial cucumber fermentations by brining salt type.

Abstract

Differences in the bacterial population of cucumber fermentations brined with no salt, 100mmoll-1 (1·1%) calcium chloride (CaCl2 ) or 1·03moll-1 (6%) sodium chloride (NaCl) were studied. Changes in the microbiology and chemistry of commercial and laboratory scale cucumber fermentations occurring as a function of time were monitored using colony counts and metagenetic analysis, and a pH probe and high-performance liquid chromatography analysis respectively. Dissolved oxygen and carbon dioxide content were monitored in commercial fermentations. Fermentations brined with calcium chloride (CaCl2 ) or no salt sustained faster microbial growth and reduction in pH than those brined with 1·03moll-1 NaCl. Leuconostoc, Lactococcus and Weissella dominated in fermentations brined with no salt or 100mmoll-1 CaCl2 on day 1 as compared to Weissella and enterobacteria in fermentations containing 1·03moll-1 NaCl. Lactobacilli dominated all fermentations by the third day, regardless of salt type, and was followed, in relative abundance by Pediococcus, Leuconostoc, Lactococcus and Weissella. From 84 to 96% of the population was composed of Lactobacillus by day 7 of the fermentations, except in the no salt fermentations in which a mixed population of LAB remained. The population of LAB found in commercial cucumber fermentations brined with 100mmoll-1 CaCl2 (n=18) or 1·03moll-1 NaCl (n=9) mimicked that of laboratory fermentations. A declining population of aerobes was detected in commercial fermentations brined with CaCl2 on day 1. A reduced NaCl content in cucumber fermentation enhances microbial diversity. This study fills a knowledge gap and aids in the design of improved reduced NaCl cucumber fermentations.