Colloidosomes potential for controlled release of ingredients
"colloidosomes", novel oil-on-oil particles in an aqueous emulsion,
as encapsulators for food.
Writing in the journal Food Hydrocolloids , researchers from the University of Massachusetts report: "We believe it may be possible to engineer interesting new functional properties into oil-in-water emulsions using this technology."
The innovative technology uses electrostatic layer-by-layer (LbL) deposition to put small oil droplets around a larger oil droplet and dispersed in an aqueous phase.
Such a technology may have important implications by reducing an emulsion's susceptibility to gravitational separation, to develop novel controlled or triggered release systems, or to compartmentalize active agents.
"These colloidosomes were produced entirely from food-grade components (corn oil, whey protein and pectin) and may therefore have applications in products that are consumed by humans, e.g., beverages, foods, pharmaceuticals and supplements," wrote lead author Yeun-Suk Gu. Talking exclusively to FoodNavigator.com, lead researcher Professor D. Julian McClements said that the technique, despite being confined to the laboratory at the moment, should be economically feasible for widespread food industry applications.
"It is based on food grade ingredients, and is simple to implement using existing technology (just pH adjustment and mixing) - so should be feasible," said Prof. McClements.
The researchers prepared the colloidosomes by mixing an oil-in-water emulsion containing large anionic (negatively charged) droplets of pectin-coated beta-lactoglobulin (whey protein) with corn oil with another oil-in-water containing small cationic (positively charged) beta-lactoglobulin with corn oil.
By maintaining the pH of the solutions around pH4.0, the pectin will adsorb to the whey protein particles.
And with increasing pectin concentrations, the charge of the droplets changed from positive to negative.
The average particle size was also affected by increasing pectin concentrations, with concentrations above 0.05 to 0.1 weight per cent giving particles about one micrometre, with no evidence of creaming.
"This suggests that the pectin was able to stabilize the droplets against aggregation by forming a relatively thick and highly charged layer around the droplets," said the researchers.
"This study suggests that colloidosomes that consist of large droplets surrounded by a layer of smaller droplets can be produced by mixing coarse and fin emulsions containing oppositely charged droplets together," they concluded.
Challenges remain to further optimize the technology, said McClements, with the most pressing being to make a stable colloidosome, without getting bridging flocculation.
Professor McClements also said that, dependent on funding, research is continuing in this area.
Source: Food Hydrocolloids Volume 21, Pages 516-526 "Formation of colloidosomes by adsorption of small charged oil droplets onto the surface of large oppositely charged oil droplets" Authors: Y-S. Gu, E.A. Decker, D.J. McClements
