Previous research has shown that formulated and natural beverages containing mixtures of anti-oxidants can produce stable levels of hydrogen peroxide (H2O2). The aim of this study was to demonstrate the ultimate anti-oxidant effects of proteins for suppressing H2O2, using a protein extract from mustard seed (Brassica juncea). The mustard seed protein isolate (MPI) contained ∼51% protein, and 6.4 mg GAe/g TS of total reducible substances, presumably representing secondary metabolites, including polyphenolics. Dose-dependent suppression of H2O2 (present at 110 µM and 550 µM), in fresh and thermally-processed orange juice was complete in the presence of 0.1 mg/mL MPI after 24 hr, with slightly higher anti-oxidant efficacy than the fruit juice-derived reference protein, thaumatin. The combination of thiol-rich amino acid (methionine and cysteine)-containing proteins and other anti-oxidant species in the MPI were highly effective for inhibiting autoxidation-mediated production of H2O2 in orange juice, and may be useful for other manufactured beverages.
Keywords: Anti-oxidant; Fruit juice; Hydrogen peroxide; Orange juice; Pro-oxidant; Protein; Redox.
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