Effect of glycosylation with apple pectin, citrus pectin, mango pectin and sugar beet pectin on the physicochemical, interfacial and emulsifying properties of coconut protein isolate

The present study aimed to investigate the effect of glycosylation with four different sources of pectin on the structural, interfacial and emulsifying properties of coconut protein isolate (CPI). The conjugates achieved the degree of graft of 59.11%, 52.80%, 41.39% and 39.26% for apple pectin, citrus pectin, mango pectin and sugar beet pectin, respectively. The covalent bonding of the conjugates was further confirmed by SDS-PAGE gel electrophoresis and FT-IR spectra. In addition, CD spectra exhibited that the conjugates had less α-helix and β-sheet, and more random coil, resulting in more flexible and loose protein structure. Attributed to glycosylation and the strong steric hindrance effects of pectin, fluorescence intensity of the conjugates decreased significantly. Moreover, the solubility, soluble free sulfhydryl content, surface hydrophobicity, emulsifying activity and emulsifying stability of the conjugates improved significantly after glycosylation. The results of adsorption kinetics showed that glycosylation could increase interfacial pressure, adsorption and rearrangement rates of CPI at the oil-water interface. In summary, the glycosylation between CPI and the four different sources of pectin can significantly improve their emulsifying properties, in particular, citrus pectin and sugar beet pectin have more significant effects.