Effects of kappa-carrageenan on egg white ovalbumin for enhancing the gelation and rheological properties via electrostatic interactions

The protein-polysaccharide system is natural, and it has been widely applied in food manufacturing in recent years. However, the interactions in the system might be affected by numerous factors and this research investigated the effects of κ-carrageenan (κ-C) on the structure, interaction, and rheological characteristics of egg white ovalbumin (OVA) before and after heating. The zeta potential was adopted to show the surface charge of mixtures and its combination with turbidity test was used to discover the maximum associative interaction at the critical mixing ratio of κ-C: OVA. The results evidenced that the electrostatic interaction formed between OVA and κ-C. The critical ratio of OVA: κ-C (w/w) at 92:8 showed the minimum net charge (−0.5 ± 0.3 mV) and the maximum turbidity (0.122 ± 0.001 cm−1). All κ-C/OVA mixtures were observed shear thinning behaviour. The mixtures at 92:8 performed the highest apparent viscosity (η) and remained the maximum complex modulus (G*) in the thermal cycle. The κ-C/OVA complex network was observed stronger than pure κ-C or OVA through the confocal scanning laser microscopy (CLSM). The rheological properties of the 92:8 mixtures supported the strongest electrostatic interactions between κ-C and OVA, corresponding to the largest aggregates structure in the CLSM images. A schematic model was further verified at the secondary structure of OVA using Fourier transform infrared (FTIR) spectroscopy. This study provides instructions to design innovative food systems that contain κ-C and OVA.