Effect of dry heating on the aggregation behaviour and aggregate morphologies of ovalbumin

Dried egg white powders are used in many segments of the food industry in place of traditional liquid egg materials. Dry heating during the processing of these products plays an essential role in obtaining their excellent functionalities, which are associated with protein aggregation. The objective of this study was to understand the aggregation behaviour of ovalbumin (OVA), the major component of egg-white proteins, during dry heating at 75 °C for 21 days. The results indicated that OVA aggregation increased from 28.7 ± 1.23% to 57.5 ± 2.45% as the reaction time increased, resulting in the generation of insoluble aggregates that were often 1-100 nm in diameter. However, a few soluble OVA aggregates became insoluble precipitates as their morphology changed from long strands to denser networks after 15 days of heat treatment. Moreover, covalent bonds, hydrophobic interactions and electrostatic repulsion played important roles in the formation of the small aggregates.