Enhancing the stability of O/W emulsions by the interactions of casein/carboxymethyl chitosan and its application in whole nutrient emulsions

The influence of Carboxymethyl chitosan (CMCS) on the emulsification stability mechanism of casein (CN) and its effects on the stability of whole nutrient emulsions were investigated. The complex solutions of CN and CMCS were prepared and the turbidity, ultraviolet (UV) absorption spectrum, fluorescence spectrum, circular dichroism (CD) spectrum, Fourier transform infrared (FTIR) spectrum, interfacial tension and microstructural observations were used to study the inter-molecular interaction of CMCS and CN. The effects of CMCS on the emulsion stability of CN were further analyzed by particle size, ζ-potential, instability index and rheological properties. Moreover, the accelerated stability of whole nutrient emulsions prepared by CMCS and CN was evaluated. The results revealed that CN-CMCS complexes were mainly formed by hydrogen bonding. The stability of the CN-CMCS composite emulsions were improved, as evidenced by the interfacial tension decreasing from 165.96 mN/m to 158.49 mN/m, the particle size decreasing from 45.85 μm to 12.98 μm, and the absolute value of the potential increasing from 29.8 mV to 33.5 mV. The stability of whole nutrient emulsion was also significantly enhanced by the addition of CN-CMCS complexes. Therefore, CN-CMCS complex could be served as a novel emulsifier to improve the stability of O/W emulsions.