Effect of pH-Shifting on Sunflower Meal Protein Isolate: Improved Stability and Interfacial Properties of Chitosan-stabilized Pickering Emulsion

Abstract

The native sunflower meal protein (SFMP) offers promising applications in food structuring and functionality. To enhance the feasibility and efficiency of SFMP utilization, this study investigated the effects of alkaline pH-shifting modification on its functional, physicochemical, and structural properties. The structural changes induced by alkaline pH-shifting were evaluated using Fourier-transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses, revealing a significant increase in the random coil content from 5.13% in native protein (NP) to 31.38% in modified protein (MP). Furthermore, pH-shifting resulted in an expansion of the crystallization area in the 20° region and a reduction in the 10° zone. Additionally, Pickering emulsions (CNPE and CMPE) produced using chitosan were found to have higher emulsion stability compared to conventional emulsions (NPE and MPE). The samples with the highest absolute ζ-potential values were CMP (52.03 ± 0.78) and CNP (52.26 ± 1.89). Notably, CMP exhibited the best emulsion stability, with particle sizes of 19.98 ± 0.92 µm and 22.29 ± 1.03 µm on the first and fourteenth day, respectively. Overall, this study successfully demonstrated the creation of stable emulsions from SFMP isolate.