SANS and SAXS: a Love Story to Unravel Structural Evolution of Soy Proteins and Polysaccharide Fibres during High Moisture Extrusion for Meat Alternatives

Plant-based meat alternatives are seeing considerable interest due to their potential to reduce environmental burden and enhance population health. The food industry, therefore, seeks routes to provide the consumer with whole-cut plant-based products that closely resemble meat products. High-moisture extrusion (HME) of plant proteins enables the industrial manufacturing of meat-like products with highly hierarchical structural organisation of fibres. The major bottleneck in serving the growing market for these products is a lack of insight into how multiscale structures evolve during shear processing. Furthermore, it remains an open question of how two biopolymers, one being a plant protein and the other being a polysaccharide, contribute to the anisotropic structure formation during HME. This study shows how the complementary use of small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS) can add clarity to these matters, benefiting from the different contrasts in scattering length density (SLD) encountered with each of these methods. It is demonstrated that two biopolymers have differences in the development of structural anisotropy. The protein fibril alignment starts in the extruder section with its further development along the cooling die. On the other hand, for polysaccharide fibres, the strongest local alignment has been found in the transition zone.