Effect of Brine Acidification on Fermentation Microbiota, Chemistry, and Texture Quality of Cucumbers Fermented in Calcium or Sodium Chloride Brines

Abstract

Commercial fermentation for bulk preservation of cucumbers relies on natural microbiota and approximately 1 M sodium chloride (NaCl) brines, resulting in large volumes of high-salt wastewater. An alternative process utilizing 0.1 M calcium chloride (CaCl 2 ) as the only salt was developed to eliminate NaCl from fermentation brines for reduced environmental impact. This study determined the effect of brine acidification on the fermentation microbiota and texture quality of cucumbers fermented in CaCl 2 brines. Cucumber fermentations were conducted in sealed glass jars for six independent lots of cucumbers in a randomized complete block design with a full-factorial treatment structure for brine acidification (acetic acid, hydrochloric acid, or nonacidified) and brining salt (1 M NaCl or 0.1 M CaCl 2 ). Enterobacteriaceae spp. survived longer and were >1 log colony forming units/mL higher in fermenting cucumbers than in brines. Addition of 25 mM acetic acid to fermentation brines (but not the addition of hydrochloric acid at the same pH) reduced Enterobacteriaceae spp. in brines and cucumbers (P < 0.002) during the initiation of fermentation for both brining salts. However, acidification had no effect on texture quality of fermented cucumbers (P = 0.8235). Despite differences in early fermentation microbiota, fermentation of cucumbers in calcium chloride brines under controlled conditions, with or without acidification, resulted in high retention of tissue firmness. These results differ from fermentations in a commercial setting initiated in brines of neutral pH, indicating that production variables, such as air exposure, interact with brining in CaCl 2 to negatively affect the texture quality of fermented cucumbers. Practical Application:This study examined the effects of initial brine acidification on the course of lactic acid fermentation and resulting texture quality of cucumbers fermented in calcium or sodium salt brines. Fermentation brines containing acetic acid (the acid in vinegar) reduced the pH of the cucumber and the soil-associated Enterobacteriaceae spp. most rapidly, and favored the conversion of sugars to lactic acid. Interestingly, the texture quality was not affected by brine acidification, and all cucumbers fermented in calcium brines in the absence of air retained their firmness during fermentation and bulk storage.Additional supporting information may be found online in the Supporting Information section at the end of the article. Table S1. Residual sugars and fermentation metabolites in fermented cucumber after 100 days for individual lots of cucumbers fermented in calcium chloride brines with or without acetic acid. 1,2

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

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Changes in the free amino acid profile of pickling cucumber during lactic acid fermentation

“…Open markers represent lactic acid, closed markers represent glucose + fructose data demonstrate that, initially, fermentation progressed more rapidly in cucumbers fermented in 2% NaCl than 6% NaCl; however, by day 7 lactic acid production in the 6% NaCl cucumbers approached that of the 2% NaCl cucumbers. Salt considerably impacts which microorganisms are selected during natural LAB fermentations, thereby influencing metabolic products and their rate of formation during fermentation (McMurtrie et al, 2019;Pérez-Díaz et al, 2013). The higher amount of salt in the 6% NaCl brined cucumbers delayed the metabolic activity of the LAB, resulting in a slower conversion of sugars to lactic acid.…”

A New Approach for Unqualified Salted Sea Cucumber Identification: Integration of Image Texture and Machine Learning under the Pressure Contact

“…For the SVM model, the radial basis function was selected as the kernel function. Through the sixfold cross-validation, the optimization of parameters of c and g is realized by using the genetic algorithm here, in which the number of iterations, the population, and the search range of c and g were set to 200, 20, 2 -10 -2 10 , and 2 -10 -2 10 , respectively [50].…”

“…With the increase in salt content, the medicinal and nutritional values of sea cucumbers are reduced [1,9]. Additionally, texture property and flavor also decline [10][11][12]. Merchants illegally use saturated salt solution to repeatedly soak sea cucumbers to increase their weight and also mix unqualified products with excessive salt contents with qualified samples to make huge profits.…”