Unravelling the digestion differences in ovalbumin gels modulated by varying saccharide chain length.

The influence of varying protein-saccharide interaction strength on the gelation properties of ovalbumin (OVA) gels was investigated using ι-Carrageenan (ι-CG) and ι-carrageenan oligosaccharides (ι-CO) as representative saccharides. Addition of both saccharides inhibited the thermal aggregation of OVA. OVA/ι-CO gels showed a lower complex modulus (G*) during gelation. Incorporating either ι-CG or ι-CO reduced the apparent viscosity, storage and loss moduli (G' and G"), hardness, and water holding capacity of the complex gels. The degradation temperature increased in OVA/ι-CG gels (332.5 °C) but decreased in OVA/ι-CO gels (317.2 °C) compared to pure OVA gels (322.8 °C). Unfolded ι-CG chains induced highly porous and irregular gel networks. Furthermore, in vitro simulated gastrointestinal digestion showed that both saccharides reduced overall protein digestibility. Specifically, at a saccharide concentration of 0.10%, gastric digestibility decreased from 26.43% to 22.32% (OVA/ι-CG) and 24.69% (OVA/ι-CO), while intestinal digestibility decreased from 80.25% to 73.65% (OVA/ι-CG) and 76.09% (OVA/ι-CO). These findings offer mechanistic insights for designing novel bio-based egg protein gels with desired texture and controlled digestive properties.