Omega-3 encapsulation: whey protein nanoparticles

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Numerous studies have shown the health benefits of essential omega-3 polyunsaturated fatty acids (n-3 PUFA), such as docosahexaenoic acid (DHA, 22:6). The trend for reduction of fat consumption calls for the enrichment of non-fat or low-fat foodstuffs with such essential nutraceuticals. New technologies need to be developed so that, without compromising the sensory properties of the enriched product, the solubilization of these bioactive compounds is favored, as well as protection against oxidation processes is conferred.

The overall goal of a research study carried out at the Israel Institute of Technology, was to develop stable nanovehicles that would solubilize, protect and possibly improve the bioavailability of DHA. For enrichment of clear, acid, aqueous foodstuffs with hydrophobic DHA, a system comprised of  β-Lactoglobulin (β-Lg) and low methoxyl pectin was designed.

Beta-Lg is a small whey protein that can bind certain hydrophobic molecules. The ability of binding DHA to β-Lg was researched on this study, and in fact it provided the first evidence for the spontaneous binding (K_b= (6.75±1.38)*10⁵ M^-1) of DHA to β-Lg.

Following this, dispersions containing entrapped DHA within β-Lg and pectin were formed. Generally, attractive biopolymer interactions may occur between positively charged proteins (pH<pI) and anionic polysaccharides. By adding an excess of low methoxyl pectin to DHA-loaded β-Lg, negatively charged particles were formed at pH=4.5, containing ~167 times higher DHA concentration than the surrounding serum. This enabled the formation of nanoparticle dispersions, which upon dilution, formed transparent solutions with 0.05% β-Lg and DHA at a 1:2 (β Lg:DHA) molar ratio. These nanoparticles presented a very good colloidal stability (zeta potential below -50mV) and had an average particle size of ~100nm.

Finally, a stress test was performed in order to assess the protection conferred by these nanocomplexes to the entrapped DHA against its oxidation. During this accelerated shelf-life test, only 5-10% DHA were lost when nanoencapsulated, compared to about 80% loss of unprotected DHA.

In conclusion, the results of this study present a new way to nanoencapsulate long chain polyunsaturated fatty acids, useful for omega-3 enrichment of clear acid drinks.

 

Source:

- P. Zimet, Y.D. Livney. Beta-lactoglobulin and its nanocomplexes with pectin as vehicles for ω-3 polyunsaturated fatty acids. Food Hydrocolloids Volume 23, Issue 4, pages 1120-1126.