Characterizing nanoscale origins of fibrous texture in high moisture extruded texturized pea protein and chicken breast meat using X-ray scattering

Consumer awareness about the origin of their food is growing. They are increasingly seeking more sustainable and climate-friendly food options, leading to a shift toward plant-based products. Texturized plant-based proteins, such as high-moisture meat analogs (HMMA), using a high-moisture extrusion (HME) process, fulfil this. However, there has been limited understanding of HMMA structure compared to that of chicken meat. Therefore, this study examines the structural features at the nanometer length scale in extruded HMMA made with pea protein, compared with those in chicken meat, using small-angle X-ray scattering (SAXS). The HME process involved varying the cooling media inlet temperatures from 60 °C to 90 °C in the custom-designed cooling die to assess their impact on the structure of pea protein HMMA. The extrudates, once cut and opened, revealed a visually parabolic fibrous structure. SAXS analyses revealed that the HMMA structure consists of semicrystalline pea protein globulins, which are packed into 30-40 nm rough spheroid-shaped particles. These particles are aggregated into interconnected mass fractal structures that show some nematic ordering, presumably forming the larger parabolic fibrous structure. In contrast, chicken had a larger particle size of ~200 nm and 5x higher nematic alignment. Moreover, the edges of the extrusion showed more densely packed semicrystalline globulin d-spacing, larger spheroid particles, and increased nematic order compared to the HMMA in the middle of the extrusion. Overall, these results point toward nanoscale origins and potential strategies of texturized plant-based proteins that increasingly mimic animal-based proteins.