Formation of γ-aminobutyric acid (GABA) during the natural lactic acid fermentation of cucumber

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

“…Gln was significantly lower in all treatments for all experiments compared with fresh cucumbers. This change was consistent with that of acidified and fermented cucumbers reported by Moore et al (2021) and was attributed to either degradation to pyroglutamic acid (pGlu) due to acidity and/or potential conversion to glu, and/or other metabolites by LAB. The most abundant free amino acids in fermented cucumber were GABA (181.3 ± 21.5 mg/kg), ile (165.2 ± 11.2 mg/kg), leu (129.8 ± 10.9 mg/kg), and lys (110.9 ± 5.0 mg/kg; Table 1).…”

“…Samples were prepared for amino acid quantification per Moore et al (2021). In summary, slurries were thawed and cryogenically ground to rupture intact plant cells and release amino acids using a Retsch mixer mill MM301 (Cole-Parmer, Vernon Hills, IL, USA).…”

“…The most abundant free amino acids in fermented cucumber were GABA (181.3 ± 21.5 mg/kg), ile (165.2 ± 11.2 mg/kg), leu (129.8 ± 10.9 mg/kg), and lys (110.9 ± 5.0 mg/kg; Table 1). The total GABA content is a function of the GABA from the fresh cucumber plus that formed from the conversion of glutamate to GABA by lactic acid fermentation after accounting for the dilution of this water-soluble molecule that occurs during pickling processes (Moore et al, 2021). On the other hand, the LAB that are prevalent in cucumber fermentation are auxotrophic for several amino acids, including ile, leu, and lys (Pérez-Díaz et al, 2017).…”

“…Proteolysis has been demonstrated during cucumber fermentation by an increase in total peptides and generation of four bioactive di-and tripeptides (Fideler et al, 2019). Additionally, changes in gln content and conversion of free glu to γ-aminobutyric acid (GABA) during LAB fermentation of cucumber has been observed (Moore et al, 2021), demonstrating the need to further understand changes in free amino acids (FAA) during fermentation.…”

Introductory Chapter: Studies on Cucumber

“…Cucumber pickles are most commonly fermented vegetable and widely consumed throughout the world [12]. Good fermentation depends on the proper combinations and interactions of multiple physical, chemical and microbiological factors [13].…”