Abstract
A casein phosphopeptide (CPP) fraction derived from tryptic hydrolysis of bovine casein was evaluated for antioxidant activity. Conjugations or mixtures of CPP with polysaccharide, galactomannan (Gal), or xyloglucan (Xyl) were prepared to evaluate potential enhancement of CPP antioxidant activity. The effect of calcium was also investigated. The CPP preparation alone was effective at scavenging hydroxyl radicals and sequestering Fe2+ to protect against Fenton reaction-induced deoxyribose oxidation in non-site-specific (up 63.3% inhibition) and site-specific (up 32.1% inhibition) binding assays, respectively. CPP also effectively quenched 2,2’-azinobis-3-ethylbenzothiazoline-6-sulfonic acid radicals (ABTS•+) to an extent of 67.6% scavenging in an aqueous system. In a soybean lecithin liposome system, CPP exhibited effective protection against peroxyl radical-induced liposomal peroxidation (38.3% of control in terms of rate of propagation). Conjugating CPP with Gal or Xyl polysaccharides using Maillard reaction conditions significantly reduced activity in the Fenton reaction-deoxyribose assays, while exhibiting no effect on the antioxidant activity of native CPP in both the ABTS and liposome assays, respectively. These results represent comparative antioxidant capacity of the native CPP and associated conjugates in phases that varied in relative hydrophilic and hydrophobic character. We conclude that CPP has the potential to act as both a primary and secondary antioxidant by displaying transition metal ion sequestering activity and free radical quenching activity. Improvements in antioxidant activity of CPP by Maillard-type conjugation with Xyl or Gal were relatively small and model-specific.
Highlights
The success of functional foods is based on the stability of targeting bioactive components in formulations and the use of technologies that will optimize the expected desired beneficial properties.Incorporation of antioxidant additives into product formulations or food package materials are examples of strategies that extend product quality and organoleptic shelf-life, which otherwise is lost due to oxidation reactions
conjugate a peptide (CPP) fractions recovered from tryptic digestion of(Figure casein 2)
Our results show that the polar multi-phosphoseryl domain, which is a characteristic requirement for metal chelating affinity and free radical scavenging for CPP in both aqueous and emulsion conditions, does not require further modification to enhance antioxidant activity
Summary
The success of functional foods is based on the stability of targeting bioactive components in formulations and the use of technologies that will optimize the expected desired beneficial properties. Incorporation of antioxidant additives into product formulations or food package materials are examples of strategies that extend product quality and organoleptic shelf-life, which otherwise is lost due to oxidation reactions. Major protein fractions present in human and bovine milk (casein and whey) and some milk protein-derived peptides have been reported to have antioxidant activity [2,3,4,5,6,7]. Specific casein hydrolysates from bovine milk demonstrate antioxidant activity via radical scavenging properties in both aqueous and lipid model systems [8,9,10,11,12,13]. Casein phosphopeptides (CPPs) derived from tryptic digests of casein have a strong affinity to sequester divalent metal ions, such
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