The effect of isolation techniques on the physicochemical properties of Moringa oleifera protein isolates

Abstract

The effect of alkaline extraction/isoelectric precipitation and salt extraction/micellization on proximate composition, anti-nutritional content, amino acid composition and physicochemical properties of Moringa oleifera protein isolates were studied. Protein extractability was influenced by NaCl concentration, pH and temperature. The protein concentration of isoelectric and micellized isolates were 80% and 90%, respectively. Micellized isolates recorded higher yields (49%) than isoelectric isolates (15%). Both isolates were free of phytate, tannin, saponin and oxalate. Micellized isolates contained all essential amino acids except lysine and methionine which met the FAO/WHO recommendations for children; isoelectric isolates were deficient in methionine. Molecular weights of protein fractions were approximately 8.5–32.5 kDa. Micellization resulted in isolates with a lighter color, higher surface hydrophobicity (184) and higher transition enthalpy (109 J/g); isoelectric precipitation resulted in isolates with a higher denaturation temperature (190 °C). The results indicated that M. oleifera protein isolates could be a potential source of plant-based protein. The differences in physicochemical properties between the isolates indicate different functionalities and potentially different applications.

Keywords

• Moringa oleifera
• Protein isolates
• Isoelectric precipitation
• Micellization
• Physicochemical properties