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Stability of heat-induced lactoferrin–sodium caseinate complexes: effects of pH and ionic strength

Zhao, Zhengtao, Lan, Haijing, Li, Quanyang, Wang, Lijun
Journal of food measurement & characterization 2018 v.12 no.3 pp. 1896-1903
calcium, functional properties, heat, ionic strength, lactoferrin, pH, sodium caseinate, sodium chloride
The interaction between lactoferrin (LF) and sodium caseinate (NaCas) can be improved by heating, which results in the formation of LF–NaCas complexes. However, the stability of those complexes under different conditions is unclear. This research investigated the stability of LF–NaCas complexes at different pHs and in different ionic environments. The results showed that stable LF–NaCas complexes can be formed at LF/NaCas ratios of 2:1 and 1:1, which have different structural and functional properties. At the ratio of 2:1, the resulted complexes were big with an average diameter of 140 ± 2.3 nm, while a much smaller average diameter of 53 ± 2.0 nm was obtained at the ratio of 1:1. At both ratios, complexes exhibited notable stability at the NaCl concentration up to 200 mmol L⁻¹. The presence of calcium is detrimental to the stability of LF–NaCas complexes. Significant precipitation was observed even at the lowest concentration of 5 mmol L⁻¹. On the other hand, both of the complexes showed great stability at pH ≥ 7.0 and ≤ 4.0, while significant precipitation happened at pH 5.0 and 6.0.