Characterization of egg white gel microstructure and its relationship with pepsin diffusivity

This study aimed to investigate how protein-based food microstructure impacts pepsin diffusion. Two egg white gels (EWGs) of identical protein concentration (10%) but different structures were used as food models. The two different gel structures were prepared by heating liquid egg white at pH5 and pH9, respectively. Results showed that egg white proteins formed a compact and microstructurally homogeneous gel at pH9 (mean particle size of 0.32 ± 0.02 μm, with a mean interparticle distance of 0.76 ± 0.07 μm), which leads to a lower FITC-pepsin diffusion coefficient (Deff = 44.2 ± 6.1 μm2 s−1), compared to the pH5-EWG (Deff = 52.5 ± 5.3 μm2 s−1). The microstructure of the pH5-EWG was characterised by a spatially heterogeneous loose protein matrix made of larger aggregate particles (mean particle size of 0.76 ± 0.07 μm, with a mean interparticle distance of 1.79 ± 0.57 μm). In addition to the effects of the EWG microstructure, the environmental pH also affects the FITC-pepsin diffusion, likely because of the impact on electrostatic interactions between pepsin and the egg white proteins.Graphical abstract
Source: Food Hydrocolloids - Category: Food Science Source Type: research