Extraction and Processing of Various Components from Egg Yolk

Abstract

An extraction procedure was investigated to separate lipid, aqueous, and protein fractions from egg yolk. Two studies were completed to determine the optimal pH and solvent ratio. The solvents used were ethanol, isopropanol (IPA), hexane-EtOH, and hexane IPA (77:23, w:w). The ratios were 1:1:1, 1:.5:2, 1:2:4, and 1:1:3 (egg yolk:solvent:water). The 1:1:1 ratio at pH 6.0 was chosen as the best with hexane-IPA giving the highest yield of egg oil. Analyses indicated that the crude lipid fraction contained 80 to 95% lipid with a high level of cholesterol (40 mg/g). The protein fraction contained 55% protein. Results of the mayonnaise tests showed that none of the fractions, alone or in combination, were as stable as emulsions made from native yolk.The crude oil fraction was degummed, refined, and bleached. The cholesterol content was reduced by 40% by refining, and free fatty acids were reduced from 3.4 to .65% after refining. Fatty acid composition analysis of the crude and unprocessed oils showed a decrease in the ratio of unsaturated to saturated fatty acids as compared to intact egg yolk. The sensory evaluation to heated egg oil indicated that further processing with improved conditions would aid the desirability of egg yolk oil as a commercial product.