Regulating the structure of soybean protein isolate-dextran maillard conjugate through cold plasma treatment: enhancing the storage and processing stability of oil-in-water emulsion loaded with curcumin.

The performance of soybean protein isolate-dextran (SPI-Dex) Maillard conjugates as O/W emulsion stabilizers is fundamentally limited by their structure and modification degree. However, cold plasma (CP) technology offers a compelling approach to overcome these limitations. Therefore, this study investigates the impact of CP treatment time on the structural and emulsifying properties of SPI-Dex conjugates to develop a high-performance, protein-based emulsion delivery system. Results indicated that compared with the control group (0 min), a CP treatment for 5 min (SPI-Dex5) reduced the disulfide bond content by 21.29 % and increased the grafting degree by 58.82 %. Analysis of the secondary structure revealed an increase in β-turn and a concurrent decrease in β-sheet content, suggesting the formation of a more flexible conformation favorable for grafting. These structural modifications contributed to an increased average particle size and a denser, pore-like architecture in the SPI-Dex5 conjugate. Consequently, emulsions stabilized by SPI-Dex5 achieved superior performance, characterized by the highest curcumin encapsulation efficiency (85.36 %), the smallest droplet size (0.71 ± 0.05 μm), and significantly enhanced rheological properties, storage and physical stability. These improvements are attributed to optimized electrostatic and hydrophobic interactions, alongside enhanced steric hindrance. In contrast, extended CP treatment (25 min) induced adverse structural changes, including re-formation of disulfide bonds and α-helices, leading to conjugate aggregation. The resultant aggregates compromised structural continuity and masked active sites, ultimately diminishing emulsifying performance. In summary, this research not only delivers a highly stable O/W emulsion for curcumin but, more importantly, deciphers the structure-property relationship of CP-modified conjugates, highlighting its vast potential for crafting advanced delivery systems.