Casein offers natural nano-encapsulation potential

By Stephen Daniells

- Last updated on GMT

Related tags: Milk

The natural ability of the milk protein, casein, to form nano-sized
micelles offers huge potential to nano-encapsulate sensitive
ingredients, say researchers from Israel.

Indeed, using fat-soluble vitamin D2 as a model hydrophobic ingredient, the researchers from the Israel Institute of Technology in Haifa, reported that the micelles could be "useful as nano-vehicles for entrapment, protection and delivery"​ of sensitive ingredients.

"Such nano-capsules may be incorporated in dairy products without modifying their sensory properties. This study introduces new possibilities for encapsulation and delivery of sensitive health-promoting substances using natural GRAS (generally regarded as safe) ingredients,"​ wrote lead author Efrat Semo in the journal Food Hydrocolloids​ (on-line ahead of print, 2006, doi: 10.1016/j.foodhyd.2006.09.006).

Food manufacturers are increasingly turning to encapsulation technologies as a way of achieving much-needed differentiation and enhancing product value. Tapping into key and emerging consumer trends with innovative techniques is becoming increasingly important for food manufacturers.

While the majority of focus has been on micro​encapsulation, more and more research is looking at the potential of nano​encapsulation.

The protein casein makes up about 80 per cent of the protein content of cow's milk (30-35 grams per litre) and is found naturally in the form of spherical micelles with diameters ranging from 50 to 500 nanometres. The stability of these micelles during processing also makes them a very attractive nano-encapsulator, indicated the authors.

Indeed, lead researcher for the study, Dr. Yoav Livney, told FoodNavigator.com that the approach is unique. Dr. Livney said that the casein micelles are designed by nature to concentrate, stabilize and deliver nutrients to the newborn.

"It's a natural way to encapsulate and deliver nutrients,"​ he said.

The researchers have applied for a patent for this "unique approach"​, and Dr. Livney confirmed that "industrial companies have already shown interest in commercializing this new technology."

The research, funded by the German-Israel Foundation, achieved non-covalent binding of the vitamin (Sigma-Aldrich) to sodium caseinate (Miprodan 30, 93.5 per cent protein, MD Food Ingredients) by adding the vitamin drop-wise to a sodium caseinate solution. The researchers used a rehydrated commercial sodium caseinate powder. This was done "in order to extend the commercial applicability of the method,"​ they said.

Semo and co-workers report that the average casein micelle (CM) diameter was 147 nm, and this increased slightly to 156 nm when vitamin D2 was added. Only 27 per cent of the vitamin added was incorporated into the nano-capsules, they said.

Moreover, Dr. Livney said that, while many microcapsules do not maintain smoothness, the small size of the nanocapsules means that they do.

The micelles were then added to a sample of reconstituted skim milk in order to test stability under ultra-high pressure homogenization. The results showed that, despite a nine per cent reduction in micelle diameter, the micelles were durable and the structure remained strong.

"Milk fortified with such vitamin D2-enriched CM accounting for only 0.6 per cent of the total milk casein would contain about one third of the vitamin D2 recommended daily allowance (RDA) for adults in a single glass (200 mL) of milk,​ said the researchers.

Dr. Livney added: "The naturally excellent digestibility of caseins and the nanoscopicsize of the micelles may improve the bioavailability of the encapsulated nutraceuticals."

And the encapsulation techniques may also be applicable to other ingredients, said Dr. Livney.

"In principle, many different hydrophobic compounds could be nanoencapsulated this way- the question is what is the purpose of the specific encapsulation (e.g. stabilization in an aqueous system, protection against deterioration, release at the right conditions etc.) flavours andaromas may be encapsulated this way, but we need to assure they will be released upon eating, and if affinity to the caseins is too high, we may not sense them,"​ he said.

"Preservatives may also be encapsulated this way, but again, if bound too strongly, they may not be active, so the precise application needs to be developed and evaluated in each case,"​ he added.

In Food Hydrocolloids​, the authors concluded: "We have demonstrated, for the first time, the possibility to load a nutraceutical compound into CM, utilizing the natural self-assembly tendency of bovine caseins.

"This study demonstrated that CM can be used for nano-encapsulation of hydrophobic nutraceutical substances for potential enrichment of low- or non-fat food products."

According to organisers of the recent Nano and Microtechnologies in the Food & Healthfood Industries conference in Amsterdam, the application of nanotechnology and nanoparticles in food are emerging rapidly.

Some analysts predict that nanotechnology will be incorporated into 16.4bn worth of food products by 2010.

However enthusiasm over the rate of progress and the possibilities is being tempered by concerns over possible downsides of the science of the miniscule, stated the Institute of Nanotechnology.

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