Kappa-carrageenan enhances the gelation and structural changes of egg yolk via electrostatic interactions with yolk protein.

The effect of κ-carrageenan (κ-C) on yolk over heat-induced gelation at natural yolk pH (6.2) and natural whole egg pH (7.5) was studied. The results showed the zeta potential values changed from -2.3 to -31.3 mV, from -8.6 to -28.6 mV for native pH yolk and pH 7.5 yolk because of the κ-C addition, respectively. These results indicated electrostatic interactions formed between protein and κ-C. The average area of holes formed by yolk gelation increased by κ-C addition. The addition of 1.0% κ-C decreased the gelling points from 62.1 to 54.4 °C, from 64.5 to 61. 6 °C for native pH and pH 7.5 yolk, respectively. A schematic model was established to show that κ-C enhances the yolk properties via electrostatic interactions. And the Fourier transform infrared (FTIR) spectroscopy verified the formation of κ-C-protein interactions. This study provides a guidance for designing novel food systems containing yolk and κ-C.