Time Evolution of Microbial Composition and Metabolic Profile for Biogenic Amines and Free Amino Acids in a Model Cucumber Fermentation System Brined with 0.5% to 5.0% Sodium Chloride

Abstract

Salt concentrations in brine and temperature are the major environmental factors that affect activity of microorganisms and, thus may affect formation of biogenic amines (BAs) during the fermentation process. A model system to ferment cucumbers with low salt (0.5%, 1.5% or 5.0% NaCl) at two temperatures (11 or 23 °C) was used to study the ability of indigenous microbiota to produce biogenic amines and metabolize amino acid precursors. Colony counts for presumptive Enterococcus and Enterobacteriaceae increased by 4 and up to 2 log of CFU∙mL−1, respectively, and remained viable for more than 10 days. 16S rRNA sequencing showed that Lactobacillus and Enterobacter were dominant in fermented cucumbers with 0.5% and 1.5% salt concentrations after storage. The initial content of BAs in raw material of 25.44 ± 4.03 mg∙kg−1 fluctuated throughout experiment, but after 6 months there were no significant differences between tested variants. The most abundant BA was putrescine, that reached a maximum concentration of 158.02 ± 25.11 mg∙kg−1. The Biogenic Amines Index (BAI) calculated for all samples was significantly below that needed to induce undesirable effects upon consumption. The highest value was calculated for the 23 °C/5.0% NaCl brine variant after 192 h of fermentation (223.93 ± 54.40). Results presented in this work indicate that possibilities to control spontaneous fermentation by changing salt concentration and temperature to inhibit the formation of BAs are very limited.

Growth of ɣ-Proteobacteria in Low Salt Cucumber Fermentation Is Prevented by Lactobacilli and the Cover Brine Ingredients

“… Pseudomonas , Serratia , Pantoea , Erwinia , Citrobacter and Enterobacter , among other bacteria were detected in fermentation cover brine samples, containing 0.9 M (5%) sodium chloride, after 6 months of storage. A reduction on the Enterobacteriaceae population was also observed by Świder and others ( 35 ) in parallel shredded cucumber fermentations brined with 90 and 270 mM (0.5 and 1.5%) sodium chloride as the sole cover brine ingredient. McDonald, Fleming and Daeschel ( 19 ) also detected viable Enterobacteriaceae in cucumber fermentations brined with 0.77 M (4.5%) sodium chloride for 3 days at 30°C.…”

“…were found to tolerate 1 M (6%) and 1.4 M (8%) sodium chloride, respectively, in Trypticase soy broth at a pH of 4.2 ( 34 ). Proliferation of Enterobacteriaceae from 6.6 ± 0.1 to 8.1 ± 0.1 log CFU/mL was observed in shredded cucumber fermentations brined with 0.9 M (5%) sodium chloride, as the only cover brine ingredient, at the suboptimal growth temperature of 23°C and a pH of about 6.5 ( 35 ). In such study, the Enterobacteriaceae population remained viable for up to 10 days, likely due to the delay in acid production to reduce the pH below 4.0.…”

A review on fermented vegetables: Microbial community and potential upgrading strategy via inoculated fermentation

“…Meanwhile, the effects of different doses of salt on microbial communities were also evident. Specifically, with the increase of salinity, the abundance of Enterobacter and Lactobacillus decreased, while that of Pediococcus , Pantoea , and Erwinia increased, which exhibited their halophilic properties (Stoll et al., 2020; Świder et al., 2021). It is certainly and widely expected that the fermentation of cucumber can be led by LAB.…”

Fermented Vegetables: Health Benefits, Defects, and Current Technological Solutions

“…It is possible to reduce the biogenic amine content of fermented vegetables by manipulating the fermentation conditions. Although salt concentration has some effects on the formation of biogenic amines in certain varieties of pickles [ 109 ], studies have found that altering the salt concentration and temperature has a limited impact on inhibiting the formation of biogenic amines in pickles [ 110 ]. Changing the formula of pickles with a relatively low precursor of biogenic amines could, then, reduce its final content.…”