O/W/O double emulsions stabilized with WPI–polysaccharide conjugates

Abstract

Protein/polysaccharide conjugates were used to stabilize oil-in-water (O/W) emulsions and oil-in-water-in-oil (O/W/O) double emulsions. By properly selecting the type of protein (WPI) and the polysaccharide (xanthan gum, fenugreek gum), and by using specific ratios of the two biopolymers and their solution concentrations, amphiphilic biopolymer adducts were formed. A synergism in the emulsification properties was observed in WPI/polysaccharide conjugates compared to each of the biopolymers alone. Submicron droplets of oil-in-water were obtained by applying a high-pressure homogenization process during the first step of the double emulsion preparation. It was also demonstrated that double-emulsion globules could be formed with a very high yield of addendum entrapment (above 95%) during the second step of the emulsification process. The differentiation between the two types of oils, O 1 (the inner) and O 2 (the outer), in the double emulsions enabled high entrapment capacity of the addendum in the inner oil phase. In addition, when the inner oil phase (O 1) was a 1:1 (w/w) mixture of MCT/triacetin and the external oil phase (O 2) was a silicone oil, it was possible to slow the release of the entrapped matter while the solubility of the inner phase in the external oil phase remained constant. The addendum solubility in the external oil phase was not a limiting factor in the release process. The presence of hydrophobic additives (i.e., 1 wt.% glycerol monooleate) in the inner oil phase helped to better control the transport to the external oil phase. In the best case, the addendum leakage to the external oil phase was only ca. 0.2 wt.% during a period of 28 days at 25 °C. WPI/xanthan gum adducts served as thick and efficient barriers against release of flumethrin ® (a veterinary drug model) entrapped in the core of the O/W/O multiple globules.