Encapsulation of resveratrol in biopolymer particles produced using liquid antisolvent precipitation. Part 2: Stability and functionality

Resveratrol is a polyphenol that is believed to have beneficial effects on human health. However, its low water-solubility and poor chemical stability hamper its use as a functional food ingredient. The goal of this study was to assess the effect of resveratrol encapsulation within biopolymer particles on its UV-induced isomerization and the effect of particle structure on particle stability to environmental stresses and redispersion of powdered particles. Biopolymer particles were formed by antisolvent precipitation of hydrophobic proteins (zein or gliadin) and coated with hydrophilic copolymers (pectin or sodium caseinate). The stability and functionality of bare zein and gliadin particles (0.5% (w/v) in suspension) were compared to zein and gliadin particles coated with sodium caseinate (1.0% (w/v)) or pectin (0.1% (w/v)), respectively. Resveratrol was encapsulated at a concentration of 250 mg/l and the effect of particle structure on resveratrol UV-stability was monitored. The suspensions of coated particles were physically stable after being held at temperatures up to 90 degrees C (30 min). Both bare protein particles and pectin coated gliadin nanoparticles aggregated when increasing the ionic strength, while sodium caseinate coated zein particle suspensions remained stable. The pH stability of the particle suspensions was related to the isoelectric point of the nanoparticles. After freeze-drying, only the sodium caseinate coated zein nanoparticles could be fully redispersed in water. All particle formulations protected resveratrol against UV-light to some extent. However, resveratrol was best protected when encapsulated in sodium caseinate-coated zein particles. In conclusion, these particles seem promising encapsulation systems to stabilize resveratrol upon supplementation to functional foods. (C) 2015 Elsevier Ltd. All rights reserved.