Effects of extrusion temperature on the structural, physicochemical and rheological properties of oat-brown rice-cod...

Extrusion of oat-brown rice-cod peptide blends (OBCB) was investigated as a practical and effective approach to produce powders with a balanced nutritional profile. Different onset extrusion temperatures (To: 90 °C, 100 °C, and 110 °C) and temperature differences (Td: 8 °C, 12 °C, 16 °C, and 20 °C) were employed to evaluate their influence on the microstructure and texture of oat-brown rice-cod peptide extrudates (OBCE), as well as the structural, rheological, water hydration, and pasting properties of oat-brown rice-cod peptide extruded powders (OBCP). Results indicated that high extrusion temperature (To and Td) yielded OBCE with higher expansion ratio and extensibility but lower density, hardness, and brittleness. A positive correlation was also observed between extrusion temperature and the water solubility index (WSI) and water absorption index (WAI) of OBCP. Furthermore, extrusion improved the reconstitutability of OBCP, with the highest values of 81.44 ± 0.21% (at To = 100 °C, Td = 12 °C) and 81.69 ± 0.42% (at To = 100 °C, Td = 16 °C), respectively. The G' and G″ values of the OBCP solution were one and two orders of magnitude higher than those of the OBCB solution, respectively, at low temperatures (30-60 °C). Concurrently, the stability temperature increased from approximately 60 °C to 75 °C. The extrusion process successfully induced starch gelatinization, as evidenced by shear tests, frequency sweeps, and Rapid Visco Analyzer (RVA). FT-IR spectra indicated a loss of short-range order, an effect exacerbated by higher extrusion die temperatures, while XRD analysis confirmed a decrease in overall relative crystallinity and a recrystallization into a V-type crystalline polymorph. This study elucidates the synergistic regulatory mechanisms of extrusion temperature parameters (To and Td) on a novel cereal-marine protein composite, providing specific technical support for the industrial production of stable, protein-rich, whole-grain-base powder products.