According to new research published in Food Hydrocolloids, including enzyme-modified sugar beet pectin in a whey-protein stabilised emulsion made the emulsions more stable to a variety of challenges, including changes in pH, thermal processing, or freezing.
“The improved stability of emulsions was mainly attributed to the stable absorption on the surface resisting attractive interactions between the droplets,” report scientists from the China Agricultural University in Beijing and the Japan International Research Center for Agricultural Sciences.
“It remains to be determined whether the presence of a cross-linked interfacial layer may alter the hydrolysis and release of encapsulated lipids and functional compounds to promote its potential applications in the food and pharmaceutical industries,” they added.
Emulsions – a mix of two unblendable liquids like oil and water – are stabilised by the addition of emulsifiers such as protein.
Emulsifiers work by stabilizing oil suspended in water, and this is achieved electrostatically. Part of the emulsifier is attracted to water, while another part is attracted to the oil. The isoelectric point (pI) is the pH at which the emulsifier has no electrical charge, and therefore in a food with a pH close to the pI the emulsifier can no longer stabilize the emulsion effectively.
According to the Chinese and Japanese scientists, cross-linking with sugar beet pectin may solve this problem, “leading to a protective shell covering the protein-stabilized droplets and thereby avoid the tendency of the adsorbed pectin layer to detach when solution conditions are varied”.
An oil-in-water emulsion was formed at neutral pH (pH 7) using whey protein isolate (Glanbia) and then coated with sugar beet pectin (Herbstreith & Fox KG) that had been treated with an enzyme from horse radish.
Results showed that the “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,” they added.
Source: Food Hydrocolloids
Published online ahead of print, doi:10.1016/j.foodhyd.2010.11.015
“A novel improvement in whey protein isolate emulsion stability: Generation of an enzymatically cross-linked beet pectin layer using horseradish peroxidise”
Authors: J-L. Li, Y-Q. Cheng, P. Wang, W-T. Zhao, L-J. Yin, M. Saito