Biomedical Engineering Reference
In-Depth Information
6 Emulsions, Nanoemulsions and Solid
Lipid Nanoparticles as Delivery
Systems in Foods
Umut Yucel, Ryan J. Elias and John N. Coupland
The functional properties of foods depend to a great extent on the presence of relatively low
concentrations of certain endogenous or exogenous small molecules. These molecules may
be classified by their function, such as flavors (e.g., limonene, citral), colorants (e.g.,
-carotene, highly
polyunsaturated fats), but many of them share the common property of producing a biological
reaction in the consumer (i.e., are bioactive). Most of these molecules are lipophilic and often
labile to oxidation, elevated temperatures or highly acidic environments. They are amongst
the most expensive ingredients in the food and their addition is critical to the economics of
the product while their loss can limit shelf life. There is, therefore, a broad need for methods
to allow these bioactive lipophilic ingredients (BLI) to be used effectively in aqueous foods.
Most of these approaches involve some form of encapsulation.
McClements and co-workers (2007) suggested an effective delivery system for BLI
should be easy to manufacture, physically stable, capable of binding useful quantities of the
molecule of interest while maintaining its chemical stability yet allowing release when
necessary (to ensure bioavailability). The delivery system should, of course, be compatible
with the food matrix and not unduly change the properties of the food. Based on these
recommendations and on the nature of BLI molecules, some inferences to the nature of
suitable delivery systems can be made. Firstly, the encapsulation should be supported by
non-covalent interactions and/or physical entrapment; covalent bonds are too strong to allow
release of the ingredient and would render it non-functional. As BLI ingredients are non-
polar, hydrophobic interactions will likely provide the basis for at least some of the binding
necessary; the encapsulation system must provide a hydrophobic domain in a hydrophilic
media. If the hydrophobic domain is to be dispersed in an aqueous food, then the
encapsulation system must allow bulk physical stability (e.g., have some hydrophilic
regions). The encapsulation system must also be small enough or share sensory properties
common to the native product, so as not to be perceived in the food. Given these constraints,
the number of delivery systems available for use with BLI in food is relatively limited and,
in practice, can be classified into three main groups.
In the first group of delivery systems, the BLI is bound directly by a food polymer
(polysaccharide or protein) and then dispersed within the food. It has been shown that the
-carotene), and increasingly phytochemicals (e.g., tea catechins,
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