High temperature curing softening salted egg yolk: Insights on microstructure, texture properties and composition of key protein

Salted egg is made by brining eggs in saturated saline for 30 days. However, producers usually increase the curing temperature of salted eggs from 20 °C to 45 °C to shorten the production cycle by nearly 50%, leading to the increase in the probability of softening salted egg yolk with a declined edible and processing quality. To elucidate the softening mechanism, this study compared the microstructure, texture properties, and composition of key proteins in non-softening salted egg yolk cured at 20 °C (NSSEY) and softening salted egg yolk cured at 45 °C (SSEY). The results showed that SSEY exhibited a higher carbonyl content, a lower free sulfhydryl content, a weaker intermolecular potential, and a smaller size of aggregates, as well as a loose network composed of numerous spheroidal nanoparticles connected in series. Salting with higher temperature also significantly decreased the water holding and protein-lipid binding capacity, with the release of more oil droplets and water. Quantitative proteomics analysis revealed an obvious decrease in the content of apolipoproteins from high-density lipoprotein (HDL) in SSEY, indicating that HDL may play a key role in the formation of SSEY.