Drug nano- encapsulation system may have food applications

03 May 2011

A method of producing nano-capsules for drug delivery may have potential to create food-grade nano-encapsulations of ingredients for the food industry, according to new research.

The study, published in LWT - Food Science and Technology, suggests that the emulsification diffusion method (EDM), used by pharmaceutical companies to create nano- scale encapsulations of active drugs, may be of use in creating food with better ingredient release profiles.

“It has been shown that the EDM is an excellent option to prepare nano-capsules from food ingredients with the potential implications that this system can have in food technology due to its capsular structure,” said the researchers, led by Dr. M. Zambrano-Zaragoza from the National Autonomous University of Mexico.

Zambrano-Zaragoza and colleagues explained that for food technologies, nano-capsules show an advantage over other nano-particulate systems – as they have an oil core which can stabilise important ingredients in food formulations.

In food technology, a nano-capsule envelope can serve as a protective barrier, that may preserve the functionality and bioavailability of food additives, or act as “an insulating membrane to prevent incompatibilities”, noted Zambrano-Zaragoza and co-workers.

Oil encapsulation

The researchers explained that food grade oils are widely used in industry, where they act as solvents for lipophilic materials including flavours, colours, antimicrobial agents, vitamins, “and many other food additives.”

“Nanotechnology, which has opened new possibilities in food preservation, is expected to have an impact on the production, processing, storage, and safety of food,” said Zambrano-Zaragoza and co-workers.

They said that a nano-capsule that modulates the release of the encapsulated ingredients – such as flavours, anti-microbials, or functional ingredients – may have applications in the formulation of foods as well as relevance in food preservation and storage.

New method

Zambrano-Zaragoza and colleagues explained that the emulsification–diffusion method (EDM), was originally developed by the pharmaceutical industry for the encapsulation of drugs.

The EDM process involves the formation of an oil-in-water emulsion between a partially water-miscible solvent saturated with water containing the drug – or in this case food ingredient – and the polymer or lipid in an aqueous solution saturated with stabilizer-containing solvent.

The addition of water to this emulsion causes the diffusion of the solvent into the external phase, with subsequent aggregation of the materials in nanoparticles.

“This technique can be attractive to design and produce nano-capsules with potential food applications,” said the authors.

Study details

The new research evaluated the potential use of the EDM to prepare nano-particles from acceptable food-grade materials, focusing on the optimal to produce food-grade nano-capsules for the potential use in food formulation.

The optimal conditions for the production of nano-capsules were at a sheer rate of 10917 s-1, with 0.5 grams per litre of polyvinyl alcohol and 256 mg of poly-e-caprolactone – This gave a predicted particle size 250 nm, with a density of 021 grams per cm3, a polydispersion index of 0.045, and zeta potential of -20.02.

Particle size increased with a decrease of shear rate and an increase of polyvinyl alcohol concentration above 0.5g/L, with a maximum particle size of 1880 nm produced at a sheer rate of 138 s-1 and 0.9 g/L of polyvinyl alcohol.

They concluded that the oil core may be used as a protective barrier to transport food additives such as colours or flavours or dietary supplements requiring encapsulation, whilst preserving their functionality and bioavailability and boosting the overall stability of the formulation.

“Formation of nano-capsules with DL-a-tocopheryl acetate and β- carotene confirmed the versatility and reproducibility of the EDM when batches with different materials are prepared under optimal conditions,” said Zambrano-Zaragoza and colleagues.

“We think that the EDM is a good option to prepare harmless and safe food nanosystems in particular biodegradable nano-capsules,” they added.

Source: LWT - Food Science and Technology