Egg yolk is well known for excellent functional properties and great nutrition values. However, the high amount of iron in egg yolk could induce oxidation and unpleasant flavour to processed food products during storage. It remains a challenge to reduce the oxidation since iron is strongly bound to phosvitin, the highly phosphorylated protein in yolk, and therefore difficult to be removed. In this tudy, two experiments using Ethylenediaminetetraacetic acid (EDTA) treatment or phosvitin extraction were proposed to separate iron from yolk and maintain the functionality at the same time.<br/>Iron content was determined by atomic absorption spectrometry. Oil droplet size and flocculation index (FI) were determined by a Mastersizer to reflect the functional properties. EDTA is a strong chelating agent and legal food additive in many countries. The first experiment showed addition of 0.025 M EDTA to egg yolk could separate 90.6% iron into a supernatant fraction with ~10% of dry mass of egg yolk. The pellet, which recovered ~90% of dry mass and 18.4% iron from egg yolk, showed comparable/better oil droplet size (0.7) and FI (9.4) with native egg yolk (oil droplet size of 11.3, FI of 8.9, smaller droplet size is favourable for emulsifying property). The protein/lipid contents of pellet were similar with native egg yolk. The second experiment was aimed to separate iron by extracting phosvitin from egg yolk. The phosvitin fraction recovered almost 100% of phosvitin with 84.5% of iron from yolk. The other two fractions (plasma and pellet) after extraction each contained less than 10% of iron from egg yolk. The oil droplet size and FI of plasma were11.0 and 7.9, and pellet were 12.6 and 8.6, which were all comparable with those of native egg yolk.<br/>Iron induced oxidation is always a problem for food products containing egg yolk. This study suggested that both EDTA treatment and phosvitin extraction could efficiently separate iron from egg yolk and maintain the functional properties. Both approaches have great potential to be applied in food processing with egg yolk.

Separation of iron from egg yolk by aqueous extraction of phosvitin or ethylenediaminetetraacetic acid (EDTA) treatment

254th National Meeting (2017)

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