Modulation of the bacterial population in commercial cucumber fermentations by brining salt type
Ilenys M. Pérez‐Díaz, Allison N. Dickey, R. Fitria, N. Ravishankar, Janet S. Hayes, Kimberley A. Campbell, Fletcher Arritt
Abstract
Differences in the bacterial population of cucumber fermentations brined with no salt, 100 mmol l−1 (1·1%) calcium chloride (CaCl2) or 1·03 mol l−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 1·03 mol l−1 NaCl. Leuconostoc, Lactococcus and Weissella dominated in fermentations brined with no salt or 100 mmol l−1 CaCl2 on day 1 as compared to Weissella and enterobacteria in fermentations containing 1·03 mol l−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 100 mmol l−1 CaCl2 (n = 18) or 1·03 mol l−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.