Elucidating how D-psicose and yeast protein modulate wheat starch gel: Mechanistic insights into formation rule, multi-scale architecture, and processing suitability

Understanding how alternative sweeteners and proteins regulate starch gelatinization is critical for developing low-sugar and functional food systems. However, the effects of D-psicose (D-psi) and yeast protein (YP) on the gelatinization behavior and multi-scale structure of wheat starch gels remain unclear. Herein, binary and ternary wheat starch (WS) gel systems containing D-psi and YP at different addition levels (1%, 3%, and 6%) were systematically investigated. The results demonstrated that the incorporation of D-psi and YP significantly altered the pasting behavior of the gels, leading to reduced viscosity parameters and increased gelatinization temperature. SEM and CLSM observations revealed that the WS-D-psi-YP systems formed a more homogeneous and compact network structure, whereas excessive D-psi induced structural collapse and heterogeneity. Meanwhile, the addition of D-psi and YP increased the short-range molecular order, decreased the relative crystallinity, and enhanced the ΔH values of the systems. Furthermore, the composite gels exhibited reduced water mobility and improved water distribution uniformity. Moderate D-psi incorporation maintained relatively stable viscoelasticity and stress relaxation behavior, while decreasing RDS and increasing SDS and RS contents. These findings provide new insights into the development of low-sugar and functional starch-based gel foods.