Physicochemical and emulsion properties of edible protein concentrate from coconut (Cocos nucifera L.) processing by-products and the influence of heat treatment

The physicochemical and emulsion properties of the edible coconut protein concentrate (CPC) obtained from coconut wet processing by-products were evaluated in order to characterize the protein. Native CPC and heat-treated CPC (CPCH) were used as an oil-in-water emulsifier at a constant protein concentration of 0.2% (w/v) in systems containing 10% (v/v) virgin olive oil or sunflower oil at pH 6.9. Nutritionally, CPC (80.3% protein) contains all the essential amino acids and predominantly leucine, lysine and valine. The coconut proteins ranged in molecular weight from 15 to 220 kDa, with both 11S and 7S globulin present. The presence of CPC as an oil-in-water emulsifier enhanced the stability of the system, and the virgin olive oil-in-water emulsions with CPC showed a higher stability than the corresponding sunflower oil-in-water emulsions. Furthermore, CPCH showed a greater solubility, interfacial tension and emulsifying activity than CPC but with a reduced emulsifying stability, particle size distribution (D-3,D-2) and flocculation. However, the protein secondary structures, zeta potential and Z-average diameter (D-4,D-3) of CPC were not significantly different from CPCH. Thus, coconut wet processing by-products can be used as a source of protein for humans, and it is possible to use the functional ingredients in oil-in-water emulsion foods. (C) 2015 Elsevier Ltd. All rights reserved.