Hydroxypropyl distarch phosphate modulates protein-starch interactions and fibrous network formation in high-moisture...

Plant-based meat analogues produced by high-moisture extrusion (HME) often exhibit insufficient fibrous texture and structural stability. This study investigated the effects of hydroxypropyl distarch phosphate (HDP) addition to a soy protein isolate-wheat gluten (SPI-WG) matrix on fibrous structure formation during HME. Formulations containing different HDP levels were evaluated for rheological behavior, textural properties, degree of texturization, water-holding and oil-holding capacities, water distribution, microstructure, intermolecular interactions, protein conformation, and thermal stability. Dead-stop sampling was further used to trace structural evolution in different extrusion zones, including the mixing, cooking, die, and cooling zones, as well as in the final extrudates. Among the tested formulations, 9% HDP showed the best overall performance, increasing the degree of texturization from 1.33 to 2.25 and achieving the highest water-holding and oil-holding capacities of 3.04 and 1.32 g/g, respectively. Mechanistic analysis indicated that HDP improved the physical mixing, hydration, and dispersion of the protein-starch matrix in the mixing zone, facilitated protein unfolding and sulfhydryl exposure in the cooking zone, and improved matrix continuity and molecular alignment in the die zone. During cooling and final structure formation, HDP favored the recovery of non-covalent interactions, β-sheet enrichment, and disulfide bond formation, thereby enhancing thermal stability. These results suggest that HDP functions as a structure-regulating starch ingredient during HME, providing a practical strategy for improving the fibrous quality of plant-based meat analogues.