Characteristics of coconut protein-enriched lipid and the effects of pH, NaCl, and xanthan gum on its dispersibility

Abstract

The poor dispersibility of coconut protein (CP) as a byproduct of industrial coconut oil production limits its use in food. In this study, we aimed to characterize the physicochemical properties of CP and improve its solubility and dispersion using pH, NaCl, and xanthan gum (XG) in the concentrations used in food. Compared with other CPs, this CP had a high fat:protein ratio, with 42% protein, 15% fat, and 32% carbohydrate (wet basis). After spray drying, increases in crystallinity and in starch–lipid interaction or starch–protein–lipid interaction in the CP powder were observed using X-ray diffraction and Fourier-transform infrared. The CP particles had a rough, irregular shape, with a wide distribution without surface cracks, and contained oil bodies. CP suspension with 2% protein was investigated. Increasing pH to 6.2 and adding 0.4–0.5 M NaCl increased the protein solubility because the pH was far from the isoelectric point, and salting-in effect occurred. However, precipitation of the CP suspension was observed. Adding 0.4% XG to CP suspension produced fluid-like behavior without precipitation by increasing the viscosity and the negative charge of surface particles. Thus, a CP–XG suspension with 2% protein could be used in the food industry, such as in protein drinks.