Changes in structure and emulsifying properties of coconut globulin after the atmospheric pressure cold plasma treatment

Abstract

Atmospheric pressure cold plasma (ACP) treatment, a non-thermal sterilization technology with great potential in coconut milk, can maximize the retention of the taste and flavour. However, it is unavoidable to have an impact on the coconut milk components. In this study, coconut globulin (CG), a component important for coconut milk stability, was selected to explore the effect of the ACP treatment on the structure and emulsifying properties of CG. After the ACP treatment, the structure of CG unfolded, which was the increase in random coils and reduction in intrinsic fluorescence intensity. In addition, the carbonyl and S–S bond content increased, while the free –SH content decreased. Compared with untreated CG (440.57 nm), the particle size of CG after the ACP treatment decreased, especially at 60 kV 60 s (207.63 nm) and 60 kV 90 s (204.20 nm). Simultaneously, poor modification and excessive modification of CG have similar surface hydrophobicity and interfacial tension to untreated CG. Notably, moderate modification (60 kV 60 s and 60 kV 90 s) resulted in the unfolding of CG molecules and the exposure of hydrophobic groups, increasing their adsorption at the oil-water interface. As expected, the emulsifying ability and emulsifying stability of CG were significantly improved after the ACP treatment at 60 kV 60 s and 60 kV 90 s. In conclusion, moderate ACP treatment could improve the emulsifying properties of CG by modifying its structure. This study provides new insights into the effect of ACP on food components during liquid food sterilization.