Extraction concentration of NaCl on structural, physicochemical and functional properties of Moringa oleifera seeds protein

Salt-soluble protein of Moringa oleifera seeds (MOSSP) was extracted by different NaCl concentration (0.2 mol/L, 0.4 mol/L, 0.6 mol/L and 0.8 mol/L) and assisted by (NH4)2SO4 salting-out procedure. The differences in the structure, physicochemical and functional properties of the MOSSP were explored. The results exhibited that there were significant differences in structural and functional properties of MOSSP extracted with different concentrations of NaCl. The protein bands extracted with higher NaCl concentration were mainly distributed below 25 kDa. MOSSP-6 presented a unique smooth spherical shape. MOSSP-2 had a compact and dense microstructure. The salt extraction concentration significantly influenced the secondary structure of MOSSP. MOSSP-6 had the highest proportion of α-helix and β-sheet (59%), and MOSSP-6 and MOSSP-8 had a more stable structure. Solubility of MOSSP was improved from 15.33% to 48.42% with the increase of extraction concentrations of NaCl. The emulsifying activity index (EAI) of MOSSP were increased from 6.01 m2/g to 9.41 m2/g and then decreased from 6.81 m2/g to 6.04 m2/g with the increase of the extracted salt concentration. These results would provide reference basis for further development and utilization of MOSSP in the food industry.