Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Research was conducted to explore ways to increase the production of the health promoting compound, gamma-aminobutyric acid (GABA), in fermented cucumber pickles. Cucumbers were fermented in reduced salt cover brines that varied in composition. GABA and its precursor molecules, glutamate and glutamine, were quantified by liquid chromatography with triple quadrupole mass spectrometry. Natural and starter culture-assisted fermentations effectively converted the intrinsic and added glutamate to GABA, while there was no microbial conversion of glutamine to glutamate under these conditions. Notably, reduced-salt cucumber fermentations with added glutamate generated ready-to-eat pickles that can deliver clinically relevant levels of GABA in a typical serving size.

Technical Abstract: Gamma-aminobutyric acid (GABA) is a non-protein amino acid with anti-hypertensive, anti-anxiety, and immunomodulatory properties. Formation of this health-promoting compound during cucumber fermentation is limited by the low intrinsic concentration of free glutamate. Glutamine is 10-fold more abundant than glutamate in fresh cucumber and may be converted to glutamate by glutaminase. Thus, the effects of brine acidification, glutamate addition, and starter culture on GABA production in fermented cucumber were investigated. Cucumbers were fermented in triplicate, in acidified (pH 4.7 – 4.8) or non-acidified (pH 6.6) cover brines with 2% (342 mM) sodium chloride (NaCl) and 0 or 10 mM glutamate. Indigenous and starter culture-assisted fermentations were conducted for each treatment at 28 °C for 7 days. The starter culture included lactobacilli containing gene sequences that encode for glutaminase (Lactobacillus gasseri ATCC 33323) and glutamate decarboxylase (Lactiplantibacillus plantarum WCFS1 ATCC BAA-793). GABA, glutamate, and glutamine were quantified by liquid chromatography triple quadrupole mass spectrometry. Both indigenous and starter culture-assisted fermentations effectively converted intrinsic and added glutamate to GABA, resulting in 10.4 ± 2.2 mM to 14.9 ± 0.7 mM in glutamate supplemented fermentations compared with 1.1 ± 0.2 mM in indigenous ferments. No additional increases in glutamate or downstream formation of GABA were observed in non-acidified brines with or without starter cultures, indicating that glutaminase production by L. gasseri and the indigenous microbiota was minimal or absent under these conditions. Glutamate addition to reduced-salt cucumber fermentations generated ready-to-eat pickles that can deliver clinically relevant levels of GABA in a typical serving size.