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

Authors: Fideler, Jennifer; DUVIVIER, RACHEL - North Carolina State University; Johanningsmeier, Suzanne

Submitted to: Journal of Food Composition and Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2020
Publication Date: 3/21/2021
Publication URL: https://handle.nal.usda.gov/10113/7185844
Citation: Fideler, J., Duvivier, R., Johanningsmeier, S.D. 2021. Formation of y-aminobutyric acid (GABA) during the natural lactic acid fermentation of cucumber. Journal of Food Composition and Analysis. 96:103711. https://doi.org/10.1016/j.jfca.2020.103711.
DOI: https://doi.org/10.1016/j.jfca.2020.103711

Interpretive Summary: Cucumber pickles are widely consumed around the globe and represent the most commonly consumed fermented vegetable in the United States. During fermentation of cucumbers, lactic acid bacteria convert the naturally occurring fruit sugars to lactic acid, lowering the pH and preserving the fruits for greater shelf stability. While the conversion of sugars to acid is well-characterized in fermented cucumbers, little is known about the changes in amino acids during fermentation and storage of these products. Gamma-aminobutyric acid (GABA) is a non-protein amino acid that may be present in both fresh and fermented vegetables and has been shown to promote antihypertensive and antianxiety effects and improve cognitive function. A mass spectrometry-based method was utilized to quantify amino acids, including health-promoting GABA in raw, acidified, and fermented cucumbers. GABA was present in fresh and acidified pickling cucumbers and additional GABA was generated in fermented cucumbers, remaining stable over time and during further processing. A survey of commercial dill pickles showed that fermented, refrigerated pickles and shelf stable fermented pickles packed in their fermentation brines had the highest GABA content. We also studied the effect of salt content on GABA formation during natural cucumber fermentation and found that brining cucumber to equilibrate to 2% NaCl produced GABA at the fastest rate and these fermented cucumbers contained more GABA than those fermented in 4 or 6% salt brines. This study shows that bioactive compounds are formed during the natural, lactic acid fermentation of cucumber; and process modifications (i.e. lower salt fermentation without desalting or brine replacement) would further enhance and retain the content of health promoting bioactive compounds in finished pickle products.

Technical Abstract: This study investigated '-aminobutyric acid (GABA) formation during natural lactic acid fermentation of cucumbers. Two lots of cucumbers were fermented or acidified in duplicate in 4 % sodium chloride (NaCl) brine and analyzed for GABA content over 6 months storage. GABA was present in fresh and acidified pickling cucumbers at 0.83 ± 0.16 mM and 0.56 ± 0.30 mM, respectively. Additional GABA was generated in fermented cucumbers (1.21 ± 0.35 mM) and remained stable over time and during further processing. Brine salt content (2 % - 6 %) affected GABA formation with greatest GABA formation in cucumber brined in 2 % NaCl (1.38 ± 0.31 mM). Commercially available, fermented cucumber pickles packed in their original fermentation brines contained more GABA (1.32 ± 0.25 mM) than acidified (0.46 ± 0.26 mM) or fermented, desalted and re-packed products (0.49 ± 0.32 mM). This work demonstrated that low-salt fermentation enhances GABA content in fermented cucumber products prepared for direct consumption.