The study, published in Food Hydrocolloids, investigated the electrostatic interactions between whey protein isolate and carrageenan when used as an emulsifier. The researchers, led by Michael Nickerson from the University of Saskatchewan, Canada, reported that the emulsion stability of a mixed system containing both carrageenan and whey protein isolate was significantly higher than individual solutions – indicating that the complex formed by carrageenan (CG) and whey protein isolate (WPI) enhanced the stability of the oil-in-water interface.
“[The] Complexes formed showed potential as an oil-in-water emulsion stabilizer, showing enhanced emulsion stability relative to individual whey protein isolate or carrageenan systems,” said Nickerson and his colleagues.
“Furthermore, the pH-sensitivity of the WPI-CG mixtures could be tailored for controlled release applications, where a WPI-CG coating could be stable at pH 4.5, and then undergo material degradation (and controlled release) at higher pHs,” they explained.
The authors noted that protein-polysaccharide interactions “play an important role in a wide range of food and biomaterial applications ranging from their structure controlling roles in food, to their use as controlled release vehicles, coatings and packaging.”
“Tailoring of such interactions is essential in order to maintain or improve ingredient functionality and/or product quality,” they explained.
Although significant research has been carried out into whey protein-polysaccharide interactions, Nickerson noted that “a fuller mechanistic understanding of the process and resulting impact on material functionality is warranted.”
They said that in general, proteins are considered effective emulsifiers at relatively low concentrations – of less than 1% – but noted that such emulsions “tend to be more prone to environmental stresses (e.g., pH, ionic strength, processing) relative to other types of surface active agents.”
The new research investigated ability of WPI with CG (kappa-, iota-, and lambda type) to form complexes in oil-in-water emulsions, and tested the stabilising ability of the complexes "to show potential for use of the formed complexes as an emulsifier.”
The authors explained that individual WPI and CG solutions acted as controls for the WPI-CG mixtures, and were prepared at equivalent concentrations and conditions as found in the mixed systems. The emulsifying properties of WPI, CD, and WPI-CG complexes were investigated in a 50/50 oil-in-water emulsion.
They said that addition of CG to the WPI solutions “caused significant changes ... as the result of the formation of soluble and insoluble electrostatic complexes.”
They reported that the mixed systems significantly enhanced emulsion stability in the mixed systems, with the greatest stability found at a 12:1 mixing ratio. At this radio, the most stable pH values were found to be between 4.5 and 4.8, with complexes dispersing below and above these values, they noted.
Nickerson explained that the formation of such complexes between whey protein isolate and carrageenan “is largely driven by electrostatic attractive forces between biopolymers of opposing net charge, with secondary stabilization most likely from hydrogen bonding, van der Waals forces and hydrophobic interactions.”
Source: Food Hydrocolloids
Published online ahead of print, doi: 10.1016/j.foodhyd.2011.08.006
“Formation and functionality of whey protein isolate – (kappa-, iota-, and lambda-type) carrageenan electrostatic complexes”
Authors: A.K. Stone, M.T. Nickerson