Electrostatic-Maillard formation of coconut protein Concentrate-Pectin conjugate for Oil-in-Water Emulsion: Effects of Ratio, Temperature, and pH

Polysaccharide protein conjugate is usually prepared by electrostatic interactions or Maillard reaction. In this study, coconut protein concentrate (CPC)-pectin conjugate was synthesized by a combination between the electrostatic and early stage Maillard reaction. The objective was to evaluate the effect of CPC-pectin ratio, temperature, and pH on emulsion stability index (ESI) and emulsion activity index (EAI). Furthermore, the obtained conjugate was used to stabilize the red palm oil emulsion. The conjugate was prepared by mixing CPC and pectin solution, and dried in a cabinet dryer. Factors, such as CPC-pectin ratio (1:3, 1:2, 1:1, 2:1, 3:1), incubation temperature (50, 60, 70, 80, 90 °C), and pH (3; 3.5; 4; 4.5; 5) were evaluated. The result show that CPC contained 67.40 ± 0.93 protein. ESI and EAI of CPC was not detected. CPC-pectin ratio, temperature, and pH had a significant effect on ESI and EAI, except temperature was not significant effect on EAI. Early stage Maillard reaction was confirmed by FTIR analysis since the peak intensity of amida I increased and amida II decreased. The best CPC-pectin conjugate was found at CPC-pectin ratio of 1:2 (w/w), incubation temperature of 80 °C, and pH of 4. ESI, EAI, droplet size and zeta potential of red palm oil emulsion were 165.263 min; 72.314 m2/g; 553.4 nm and −45.5 mV, respectively. The emulsion droplets were uniform in size and equally dispersed. In summary, drying of conjugate on cabinet dryer induced early stage Maillard reaction and the conjugate can be used to stabilize red palm oil emulsion.