Beta-lactoglobulin and its nanocomplexes with pectin as vehicles for omega-3 polyunsaturated fatty acids

The reduction of fat consumption calls for enrichment of non-fat foods and beverages with essential oil-soluble nutraceuticals, including omega-3 fatty acids. However, the low water-solubility and sensitivity to oxidation require new ways to solubilize and protect such sensitive compounds without compromising the desired sensory attributes of the enriched product. Beta-lactoglobulin (beta-Lg), the major whey protein of cow milk, is a natural molecular nano-carrier for hydrophobic molecules. The present work provides apparently first evidence for the spontaneous binding (K-b = (6.75 +/- 1.38) x 10(5) M-1) of docosahexaenoic acid (DHA) to beta-Lg. Based on a recent study from our group [Ron, N. (2007). beta-Lactoglobulin as a nanocapsular vehicle for hydrophobic nutraceuticals. M.Sc. thesis, Advisor: Dr. Yoav D. Livney, The Technion, Israel Institute of Technology. Haifa, Israel], we herein show the formation of colloidally stable nanocomplexes of DHA-loaded beta-Lg and low methoxyl pectin below the isoelectric point of beta-Lg (5.2), at pH = 4.5. By adding excess of pectin, negatively charged particles were formed containing similar to 166 times higher DHA concentration than the Surrounding serum. This enabled the formation of dilutable nanoparticle dispersions, which formed transparent solutions containing 0.05% beta-Lg and DHA at a 1:2 (beta-Lg:DHA) molar ratio, with a very good colloidal stability and average particle size of similar to 100 nm. The entrapment by beta-Lg, and moreover, the formation of nanocomplexes with the pectin provided good protection against degradation of DHA during an accelerated shelf-life stress test: only about 5-10% lost during 100 h at 40 degrees C, compared to about 80% lost when the unprotected DHA was monitored. This study presents a new way to nanoencapsulate long chain polyunsaturated fatty acids like DHA, useful for enrichment of clear acid drinks. (C) 2008 Elsevier Ltd. All rights reserved.