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Research Project: Improved Processes for the Preservation and Utilization of Vegetables, Including Cucumber, Sweetpotato, Cabbage, and Peppers to Produce Safe, High Quality Products with Reduced Energy Use and Waste

Location: Food Science Research

Title: Discovery and quantification of bioactive peptides in fermented cucumber by direct analysis IR-MALDESI mass spectrometry and LC-QQQ-MS

Author
item FIDELER, JENNIFER - North Carolina State University
item Johanningsmeier, Suzanne
item EKELOF, MANS - North Carolina State University
item MUDDIMAN, DAVID - North Carolina State University

Submitted to: Journal of Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2018
Publication Date: 1/1/2019
Publication URL: http://handle.nal.usda.gov/10113/6109465
Citation: Fideler, J., Johanningsmeier, S.D., Ekelof, M., Muddiman, D.C. 2019. Discovery and quantification of bioactive peptides in fermented cucumber by direct analysis IR-MALDESI mass spectrometry and LC-QQQ-MS. Journal of Food Chemistry. 271:715-723. https://doi.org/10.1016/j.foodchem.2018.07.187.
DOI: https://doi.org/10.1016/j.foodchem.2018.07.187

Interpretive Summary: Health-promoting compounds composed of particular short chains of amino acids are known as bioactive peptides. Bioactive peptides possessing therapeutic properties are well documented in foods fermented by lactic acid bacteria, including dairy products, sourdough, and cured meats, but have not been previously investigated in fermented vegetables. Cucumber pickles, the most commonly consumed fermented vegetable in the United States, are not amenable to analytical workflows used for the analysis of peptides without extensive sample preparation, due to their high salt content. A novel mass spectrometry based method was used for direct analysis of peptides in acidified and fermented cucumbers. Five short peptides with known anti-hypertensive properties were identified in fermented cucumber: lysine-proline, isoleucine-proline-proline, leucine-proline-proline, valine-proline-proline, and arginine-tyrosine. An advanced analytical method for quantifying these peptides in fresh, acidified, and fermented cucumbers was developed and the results showed that 4 of the 5 bioactive peptides were uniquely present in fermented cucumber. Bioactive peptides, although present at low concentrations compared to other food constituents, may be valuable functional food components due to their high potency. Further research is needed to determine if these compositional changes during lactic acid fermentation are in sufficient quantities for a health benefit.

Technical Abstract: Bioactive peptides have been identified in lactic acid bacteria fermented foods including cultured milk, sourdough, and cured meats; however, their presence has not been investigated in fermented vegetables. In this study, infrared, matrix-assisted laser desorption electrospray ionization (IR-MALDESI) mass spectrometry (MS) was employed to identify bioactive peptides in fermented cucumber. Natural and starter culture fermented cucumbers were prepared in triplicate in sodium chloride brines and compared to acidified cucumbers. Putative matches of known food-derived bioactive peptides were identified by direct analysis using IR-MALDESI-MS. Peptides were confirmed by IR-MALDESI MS/MS and quantified by LC-MS/MS. Three angiotensin converting enzyme (ACE) inhibitory peptides, IPP (0.42–0.49 mg/kg), LPP (0.30–0.33 mg/kg), and VPP (0.32–0.35 mg/kg) were formed in fermented cucumbers. A fourth ACE inhibitory peptide, KP (0.93–1.5 mg/kg), was enhanced 3–5 fold in fermented cucumbers compared with acidified cucumbers. This work demonstrates that lactic acid bacteria fermentation can enhance bioactive peptide content in vegetables.