Thermal-aided phosvitin extraction from egg yolk.

Phosvitin is the principal phosphoprotein in egg yolk and has great potential for use as a functional food ingredient in improving bone health. This study reports a thermal-aided extraction method without using organic solvents or non-food-compatible chemicals. Egg yolk was two times diluted with water and then extracted by 100 g L(-1) NaCl. Effects of pH and heating temperature on the extract were examined. The phosvitin purity increased from 75.7% at pH 8.0 to 80.1% at pH 5.0 and then started to decrease, but the yield decreased at decreasing pHs. The phosvitin purity increased at increasing temperature up to 90 °C and then started to decrease at 95 °C, while the yield increased from 70 to 80 °C and then started to decline at 85 °C. A purity of 88.0% and a yield of 23.5 g kg(-1) yolk dry matter were obtained at 90 °C. The purity and yield were comparable to or higher than those of previously methods. The method developed in this study is simple, including mainly two steps, i.e. water dilution of egg yolk and NaCl extraction with heating, and can be scaled up for industrial production.