Neutrons and Food 8 at MLZ

SAXS remains challenging for complex systems such as EYG and casein fusion proteins. It provides quantitative insights into intermediate structures and internal organization and allows a statistical description of the dynamic fine structure of macroscopic complexes, especially relevant for our artificial casein microparticles and fibres used for enzyme immobilization.
We investigated native and lyophilized egg yolk granules (EYG) as well as recombinant casein fusion proteins using SAXS. In EYG, lyophilization led to a loss of LDL and expansion of HDL structures, as indicated by Porod exponents and peaks at q ~0.019–0.037 Å- 1. Functional tests confirmed stable oil-in-water emulsions after rehydration. Higher EYG concentrations resulted in smaller droplets and improved stability.
In the SAXS curves of casein fusion proteins, the intrinsically disordered casein moieties curves could be described by modified Lorentz functions, while compact fusion proteins were modelled with spherical shape factors, considering known radii of gyration. Further analyses showed that these fusion proteins can be successfully incorporated into microparticles and fibres. We report on the influence of the nano- and aggregate structure on porosity and distribution within the functional materials.
Elucidation of the average nano- and aggregate structure enables the targeted production of sustainable, functional foods and recombinant casein biopolymer constructs for biocatalysis and enzyme immobilization.