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Article
Antioxidant Activity of Cysteine, Tryptophan, and Methionine Residues in Continuous Phase Beta-Lactoglobulin in Oil-in-Water Emulsions
Journal of Agricultural & Food Chemistry (2005)
  • Ryan J. Elias
  • D. Julian McClements, University of Massachusetts - Amherst
  • Eric A Decker, University of Massachusetts - Amherst
Abstract

Proteins dispersed in the continuous phase of oil-in-water emulsions are capable of inhibiting lipid oxidation reactions. The antioxidant activity of these proteins is thought to encompass both free radical scavenging by amino acid residues and chelation of prooxidative transition metals; however, the precise mechanism by which this occurs remains unclear. In this study, the oxidative stability of cysteine, tryptophan, and methionine residues in continuous phase β-lactoglobulin (β-Lg) in a Brij-stabilized menhaden oil-in-water emulsion was determined. The presence of low concentrations of continuous phase β-Lg (250 and 750 μg/mL) significantly inhibited lipid oxidation as determined by lipid hydroperoxides and thiobarbituric acid reactive substances analysis. It was observed that cysteine oxidized before tryptophan in β-Lg, and both residues oxidized before lipid oxidation could be detected. No oxidation of the methionine residues of β-Lg was observed despite its reported high oxidative susceptibility. It is conceivable that surface exposure of amino acid residues greatly affects their oxidation kinetics, which may explain why some residues are preferentially oxidized relative to others. Further elucidation of the mechanisms governing free radical scavenging of amino acids could lead to more effective applications of proteins as antioxidants within oil-in-water food emulsions.

Keywords
  • Amino acids; antioxidants; β-lactoglobulin; lipid oxidation; protein oxidation; emulsions
Disciplines
Publication Date
November 22, 2005
Publisher Statement
DOI: 10.1021/jf0521698
Citation Information
Ryan J. Elias, D. Julian McClements and Eric A Decker. "Antioxidant Activity of Cysteine, Tryptophan, and Methionine Residues in Continuous Phase Beta-Lactoglobulin in Oil-in-Water Emulsions" Journal of Agricultural & Food Chemistry Vol. 53 Iss. 26 (2005)
Available at: http://works.bepress.com/djulian_mcclements/135/