Emulsion stabilizing properties of pectin

Citrus pectin and beet pectin are able to reduce the interfacial tension between an oil phase and a water phase and can be efficient for the preparation of emulsions. Investigations were made to evaluate the effect of various parameters of pectin on its emulsifying capacity. Orange and rapeseed oils emulsions were prepared with pectin as an emulsifier. They were then separated by centrifugation and the pectin fraction remaining in the aqueous phase was analyzed. It was found that the molecular weight, protein and acetyl contents influenced significantly the emulsifying properties. It was observed that for both citrus and beet pectin, the fraction which became associated with the oil contained much more protein than the fraction in the aqueous phase. It is suggested that protein associated with the pectin played a key role in the stabilization of the emulsion. Our experiments indicated that depending on the pectin source, beet or citrus, only a limited quantity is adsorbed on the oil surface. The de-acetylated beet pectin maintained a good emulsifying ability but the chemically acetylated citrus pectin gave better results than the non-acetylated citrus pectin. It was inferred that acetyl groups could also contribute to emulsion stability. It is likely that they act by reducing the calcium bridging flocculation. A model is proposed to explain the emulsifying function of pectin.