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

• Published in: Food hydrocolloids 2020-01, Vol.98, p.105258, Article 105258
• Main Authors: Somaratne, Geeshani, Nau, Francoise, Ferrua, Maria J., Singh, Jaspreet, Ye, Aiqian, Dupont, Didier, Singh, R. Paul, Floury, Juliane
• Format: Article
• Language: English
• Subjects: Diffusion coefficient; Egg white gel; Electrostatic interactions; Food and Nutrition; Food engineering; FRAP; Life Sciences; Pepsin
• ISSN: 0268-005X; 1873-7137
• DOI: 10.1016/j.foodhyd.2019.105258

Understanding the diffusion of digestive enzymes, particularly pepsin, in different food structures, is a key factor to better control protein digestion and absorption. 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. [Display omitted] •First quantitative characterization of the microstructural parameters of EWGs•PH5-EWG exhibited a porous structure and pH9-EWG exhibited a compact microstructure•Diffusivity of pepsin is significantly higher for the pH5-EWG than the pH9-EWG•Electrostatic interactions occur between the pH5-EWG proteins and FITC-pepsin•Pepsin diffusivity is modulated by the gel microstructure and environmental pH