Influence of heat treatment and egg matrix on the physicochemical and allergenic properties of egg custard.

To investigate the influence of heat treatment and egg matrix on egg custard (EC) proteins, 12 different kinds of ECs with different egg/water ratios (1:1, 1:1.5, 1:2, or 1:3, v/v) and different heating temperatures (80, 90, or 100 °C) and times (10, 15, or 20 min) were prepared and evaluated for the digestibility, structure, eliciting capacity and sensitizing capacity using SDS-PAGE, fluorescence spectra, ELISA, and a BALB/c mouse model, respectively. The physicochemical properties of EC proteins were significantly affected by heat treatment and egg matrix, which showed the increased digestibility and partially unfolded structure. The eliciting capacity of EC evaluated by IgE binding to sera from egg-allergic patients was reduced after heat treatment, and the EC made by heating at 100 °C for 20 min with a whole egg/water ratio of 1:2 (v/v) was the weakest. The sensitizing capacity of EC was also reduced in the BALB/c mouse model, which showed the significantly decreased levels of specific IgE, IgG, IgG1 and IgG2a, mMCP-1 and histamine in the mouse sera, as well as cytokine secretions of IL-4, IL-5, and IL-13, compared with the raw egg (RE) group. Results demonstrate that heat treatment and egg matrix significantly reduced the eliciting and sensitizing capacity of EC by changing the tertiary structure and increasing the digestibility of EC proteins. PRACTICAL APPLICATION: Egg custard (EC) is one kind of savory food suitable for all ages, and is also a traditional supplementary food for infants and young children in China. However, limited information is available on the allergenicity of egg custard. In this work, we evaluated how the structure, digestibility, and allergenic potential of egg allergens in EC were altered by the degree of thermal treatment and egg matrix, and elucidated the links between the physicochemical properties and allergenic potential of EC affected by heat treatment and egg matrix. Our results demonstrate that heat treatment and egg matrix significantly reduced the eliciting and sensitizing capacity of EC by changing the tertiary structure and increasing the digestibility of EC proteins.