Fabricating a high internal phase-like emulsion using aggregated rice bran protein modified by ultrasound-assisted protein-glutaminase deamidation

Given the demand for developing stable liquid oil solidification systems and the existing application limitations of large-sized aggregated proteins, this study investigated the regulatory effects of protein-glutaminase (PG) deamidation combined with ultrasound modification on the structure of aggregated rice bran protein (AP) and the stability of high internal phase-like (HIP-like) emulsion systems. The structural properties, interfacial characteristics of AP, and macroscopic performance of HIP-like emulsion were systematically characterized. The results showed that deamidation induced the conformational unfolding of AP molecules, promoted the transformation of β-sheet to β-turn structure, and slightly increased the surface negative charge density. Ultrasound regulated the aggregation state of AP and facilitated the formation of uniform and controllable protein aggregates. Furthermore, the synergistic effect of ultrasound and deamidation enabled AP to form well-structured aggregates, which remarkably improved the surface hydrophobicity and interfacial film strength, laying a structural foundation for optimizing the three-dimensional network structure of emulsions. In addition, the modified AP HIP-like emulsion exhibited lower oil phase volume of approximately 60%, enhanced centrifugal stability, and excellent rheological properties. In conclusion, the combined modification of ultrasound and deamidation could strengthen interfacial film formation and construct a stable three-dimensional network structure by regulating the conformation and aggregation state of AP, thereby effectively improving the stability and moldability of HIP-like emulsion. Specifically, deamidation played a dominant role in regulating emulsion performance. This study provided a theoretical basis for the utilization of large-sized aggregated plant proteins and the development of high-performance plant protein-based liquid oil solidification systems and low-fat food products.