Enzymatic Deamidation Enhances Hydrogen Bond Networks of Glutinous Rice Flour and Soy Protein Isolate in Oleogels: Mechanism and Butter Replacement

Abstract

Driven by the rising demand for healthy diets, vegetable oil-based oleogels as animal fat substitutes have attracted increasing research attention. In this study, a starch-protein composite oleogel was prepared by emulsion templating using protein-glutaminase (PG)-modified glutinous rice flour (GRF)/soy protein isolate (SPI) complex as the gelator. The effects of deamidation degree and flour/protein ratio on the properties of PG-modified GRF/SPI emulsions (PG-GRPE) and oleogels (PG-GRPO) were systematically investigated. The absolute ζ-potential reached a maximum of ± 36.85 mV at 40% SPI substitution. Notably, deamidation significantly enhanced the oil-binding capacity of the oleogel from 24 to 98%. The optimal PG-GRPO formulation was 14% deamidation, 40% SPI substitution, and pH 6.0, exhibiting physicochemical and mechanical properties most similar to those of commercial butter. The dough prepared with PG-GRPO exhibited no significant differences in springiness, gumminess, and chewiness compared with the butter-based dough, and the finished cookies displayed a butter-like appearance and texture. Sensory evaluation further revealed no significant differences between the PG-GRPO and butter cookies for the assessed attributes, including surface color, appearance, internal structure, and odor. This research clarifies the formation mechanism of PG-modified starch-protein hydrogen bond gel networks, provides theoretical and technical support for developing plant-based oleogel as animal fat alternatives.