Influence of physicochemical conditions and technological treatments on the iron binding capacity of egg yolk phosvitin

The iron binding capacity of egg yolk phosvitin was evaluated at different conditions of pH (3.0-7.0) and ionic strength (0.10-0.60). The best value was obtained at pH 6.5 and 0.15 M of ionic strength (115 mug of iron/mg of phosvitin). For pH values under 3.5, iron fixation was slow and weak. When increasing ionic strength at pH values higher than 5.2, iron binding capacity was weakened. On the contrary, between 5.2 and 3.5 of pH values, the higher the ionic strength, the better the iron fixation. Once iron was fixed in favourable conditions, further acidification does not modify iron binding capacity of phosvitin. Only the presence of a strong chelating agent could remove iron from phosvitin. Phosvitin treated by thermal or high pressure methods did not result in aggregation and kept its high iron binding capacity, even at the strongest treatment conditions (90 degreesC or 600 MPa). (C) 2003 Elsevier Ltd. All rights reserved.