A novel improvement in whey protein isolate emulsion stability: Generation of an enzymatically cross-linked beet pectin layer using horseradish peroxidase

Extensive research has indicated that the electrostatic attraction between polysaccharides and proteins on the oil–water interface can improve the stability of emulsions. However, this electrostatic effect will be weakened or even eliminated as the solution pH or ionic strength of emulsions change, resulting in the shedding of the polysaccharide layer. We prepared primary oil-in-water emulsions at pH 7.0 using whey protein isolate (WPI) as an emulsifier and then beet pectin was added to form secondary emulsions. After the pH of emulsions was adjusted to 4.0 to promote electrostatic attraction between the beet pectin molecules and the protein-coated droplets, horseradish peroxidase was added to generate a cross-linked beet pectin coating. Results show that stable emulsions coated with WPI and cross-linked beet pectin interfaces could be formed. The sensitivity of the emulsions to the environmental stresses of pH changes, ions addition, thermal processing and freezing was also characterized in this work. Our results support the view that cross-linked beet pectin improves the stability of emulsions and is superior to simple deposition on the surface of lipid droplets. The interfacial engineering technology used in this study could be used to create food emulsions with improved stability to environmental stresses.