Electrophoretic and Chromatographic Changes in Egg Yolk Proteins Due to Heat

ABSTRACT Polyacrylamide gel electrophoresis and diethylaminoethyl‐cellulose ion‐exchange chromatography were used to observe changes in egg yolk products which were heat treated at 3°C intervals from 54 to 84°C for 3.5 min. The USDA pasteurization temperatures of 61.0, 63.3°C for plain, 10% sugared, and 10% salted egg yolk, respectively, had little effect on their electrophoretograms. Only the γ‐livetins in plain yolk were slightly affected. Higher temperatures progressively altered these proteins until they disappeared from the electrophoretograms from plain yolk ca 73°, sugared yolk ca 76°, and salted yolk ca 79°C. The lipovitellin fraction and phosvitins were similarly affected by increasing temperatures. Sugar and salt at 10% levels had a protective effect against heat, allowing respectively ca 3° and 6°C higher temperatures before heat damage occurred. The chromatograms from plain and sugared yolk were little affected by pasteurization. However, major changes were noted between unheated and pasteurized (63.3°C) salted yolk. Patterns for salted yolk, pasteurized at 63.3 and 68.0°C were similar, which further indicated that this product can be pasteurized at 68.0°C without significant damage.