Thermally-induced β-lactoglobulin-EGCG nanovehicles: Loading, stability, sensory and digestive-release study

(-)-Epigallocatechin-3-gallate (EGCG), which has been attributed with numerous health benefits, is an oxidation sensitive, water soluble polyphenol. We have recently shown that heat-denatured beta-Lactoglobulin (beta-Lg) forms nanoparticles (<50 nm) with EGCG, which confer considerable protection to EGCG against oxidative degradation, useful for clear beverage enrichment. The current study aimed at advancing our understanding by further characterizing the structure, properties and performance of this new nanodelivery system to facilitate its application. We found that although particle size increased with rising EGCG concentration, zeta potential (based on the Smoluchowski model) stayed around -40 mV up to 8: 1 M EGCG:beta-Lg ratio, suggesting particles are very stable in solution. Good loading efficiency (60 -70%) of EGCG within beta-Lg nanocomplexes was obtained. The loading efficiency was mostly dependent on beta-Lg concentration. Freeze-dried nanoparticles showed an IR absorbance spectrum different from the spectra summation of the pure components, confirming the molecular level complexation. Following freeze drying, the reconstituted complexes were very similar in size to the pre-frozen ones. The nanoentrapment dramatically suppressed the bitterness and astringency of EGCG. Simulated gastric digestion of beta-Lg-EGCG nanoparticles showed limited release of EGCG, suggesting they could potentially be used as vehicles for protection of EGCG in the stomach, and for its sustained release in the intestine. Our results suggest that denatured beta-Lg may serve as an effective natural vehicle for nanoencapsulation, protection and sustained release of EGCG and possibly other polyphenols for clear beverage enrichment. (C) 2012 Elsevier Ltd. All rights reserved.