Abstract

ABSTRACTIsolates of reduced‐cholesterol egg yolk were prepared by extracting cholesterol from spray‐dried yolk using the following solvents: (1) petroleum ether, (2) petroleum ether/ethanol, (3) ethanol/water and (4) supercritical carbon dioxide. Differential scanning calorimetry demonstrated that the temperature of minimum heat flow of the denatured isolates was about 75C. Mechanical properties of extracts were compared using small deformation oscillatory rheology. Ethanol/water and petroleum ether treated yolk had the strongest and weakest gelling characteristics respectively, following protein denaturation at 75C. When compared to egg white, yolk isolates formed stronger networks at 75C. Heating at higher temperatures denatured ovalbumin which produced slightly stronger gels than egg yolk. Binary mixtures of egg white and yolk formed phase separated gels. The best agreement between experimental data and calculated composite moduli by using isostrain and isostress Takayanagi models, was obtained for egg white keeping 37% more water per unit concentration than the egg yolk.

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