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56 2017

Journal of Food and Nutrition Research
Súhrny čísla 2 / 2017

Udenigwe, C. C. – Gong, M. – Mohan, A. – Udechukwu, M. C.
Role of surface charge of hydrolysed bovine caseins in their iron(II)-binding affinity and antioxidative capacity in iron(II)-facilitated beta-carotene and glutathione oxidation
Journal of Food and Nutrition Research, 56, 2017, č. 2, s. 149-154

Chibuike C. Udenigwe, School of Nutrition Sciences, Faculty of Health Sciences, University of Ottawa, 25 University Private, Ottawa, Ontario, K1N 6N5, Canada; Department of Plant, Food, and Environmental Sciences, Faculty of Agriculture, Dalhousie University, 50 Pictou Road, Truro, Nova Scotia, B2N 5E3, Canada. E-mail: cudenigw@uottawa.ca

Received 2 December 2016; 1st revised 16 February 2017; accepted 11 March 2017; published online 3 May 2017

Súhrn: Surface properties of peptides can affect their functionality, including metal-binding capacity. Casein hydrolysed with five proteases had varying surface hydrophobicity (from 56.4 ± 3.1 to 157.0 ± 16.8) and surface charge (zeta-potential, from –43.5 mV ± 0.5 mV to –32.5 mV ± 0.6 mV). The hydrolysates had varying Fe2+-chelating capacity (from 0.049 mg·ml-1 ± 0.005 mg·ml-1 to 0.134 mg·ml-1 ± 0.027 mg·ml-1); the best activities were observed for hydrolysates with the highest surface hydrophobicity. Maximum specific ligand binding (Bmax) of the samples appeared to be independent of surface charge and hydrophobicity. However, ligand dissociation constant (Kd) of the peptide-Fe2+ complex strongly correlated with zeta-potential (rs = 0.90). This suggests that the negatively charged surface of the particles facilitated peptide-Fe2+ chelate complex formation via electrostatic interaction. Casein hydrolysates with the lowest Kd and zeta-potential displayed the maximum capacity for inhibiting Fe2+-facilitated oxidation of beta-carotene, suggesting that strong Fe2+-binding by the peptides made the pro-oxidant metal less available for participation in oxidation. However, this relationship was not observed for their inhibition of Fe2+/H2O2-induced glutathione oxidation, likely due to peptide inaccessibility to the anionic glutathione. The findings show that surface chemistry of hydrolysed caseins affects their interactions with pro-oxidant iron, which is an important consideration for their use as antioxidants in foods.

Kľúčové slová: casein hydrolysate; iron chelation; beta-carotene oxidation; glutathione oxidation; binding affinity; surface charge

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