Preparation of water-in-oil-in-water (W1/O/W2) double emulsions containing trans-resveratrol

trans-Resveratrol (3,5,4′-trihydroxystilbene) is a naturally occurring polyphenol phytoalexin easily oxidizable and extremely photosensitive with a short biological half-life. The goal of this work was to prepare W1/O/W2 double emulsions of food-grade formulation to encapsulate trans-resveratrol. Mechanical agitation and membrane emulsification (ME) were the techniques used for emulsion preparation. A technique based on RP-HPLC to determine trans-resveratrol concentration in the external aqueous phase with UV–vis and fluorescence detectors was developed. Several inner emulsifiers were tested to produce stable water-in-oil (W1/O) emulsions containing 20% (v/v) of ethanol. Polyglycerol polyricinoleate (PGPR) was the only emulsifier with good stabilizing properties. Non-ionic surfactants (Tween 20 and Tween 80) were used as outer emulsifiers. Other food bioemulsifiers, such as sodium caseinate (NaCn), sodium carboxymethylcellulose (CMCNa) or gelatin, were also added as stabilizers to improve W1/O/W2 double emulsions stability. Initial encapsulation efficiency (EE) and encapsulation stability (ES) were measured. The combination of Tween 20 and CMCNa in the external aqueous phase seemed to have a synergetic effect leading to better initial EE values. More stable emulsions were obtained with mechanical agitation. An increase in PGPR content yielded a slight increase in initial EE values.