Effect of food additives on egg yolk gelation induced by freezing.

This study demonstrates technological advances in preventing yolk gelation during freezing and thawing. Gelation negatively affects yolk functionality in food formulation. Preventing gelation using 10% salt or sugar limits the application of the yolk. Novel food additives were tested to prevent gelation induced by freezing. Significant reduction (p < 0.05) in gel hardness of frozen-thawed yolk (45 h freezing at -20 °C) indicates that hydrolyzed carboxymethyl cellulose (HCMC), proline, and hydrolyzed egg white and yolk (HEW and HEY) are effective gelation inhibitors. The mechanisms in which these additives prevented gelation were further studied through measuring the changes in the amount of freezable water, lipoprotein particle size, and protein surface hydrophobicity. Overall, this study provides several alternatives of gelation inhibitor that have great potentials in replacing the use of salt or sugar in commercial operation of freezing egg yolk for shelf-life extension.

Use of Reconstitued Yolk Systems To Study the Gelation Mechanism of Frozen-Thawed Hen Egg Yolk.

Yolk gelation upon 5 week freezing-thawing was studied in four recombined yolk systems containing different plasma and granule proportions. Fractionation for mass distribution, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) for protein distribution, and rheological properties were explored. Results indicate that both plasma and granule components, including low-density lipoprotein (LDL), high-density lipoprotein (HDL), and α-livetin proteins, contributed to gelation. Protein aggregation was reflected through a large mass increase in the granule fraction and appearance of a floating LDL layer upon fractionation of gelated yolk systems. A significant increase in gel strength (elastic modulus, G') was observed with the increase of the granule content. Overall, this study provides a better understanding of yolk gelation mechanism that may consequently lead to the design of innovative methods for preventing gelation. A schematic presentation of the yolk gelation mechanism is also proposed.