Stabilization of W/O/W multiple emulsion loaded with Hibiscus sabdariffa extract through protein-polysaccharide complexes

In this work, a hydrophilic anthocyanidin-rich extract from Hibiscus Sabdariffa (H. sabdariffa) was vehiculized in the inner phase of a water/oil/water emulsion and its physical stability was improved by means of the reinforcement of both interfaces, the oil-water and the water-oil one, with whey protein concentrate (WPC)-arabic gum (AG) complexes. To this end, the main critical parameters involved on destabilization mechanisms for emulsions have been considered, e.g. the active ingredient concentration, the emulsifier amount and ratio, the biopolymers concentration and ratio (WPC:AG), and the pH value during emulsification. Stable and constant values of average droplet volume diameter (d4,3) around 6.47-8.54 μm after 30 d of storage at room temperature were obtained for multiple emulsions containing 20 and 10 g/100 g of extract concentration, respectively. The pH was found to play an important role in the long-term stability. Indeed, the higher long-term stability parameters were achieved at pH of 4.5, value in which the WPC and GA result in maximum complex formation. Thus, the stabilization of water/oil/water multiple emulsions containing H. sabdariffa extract through WPC and AG complexes was confirmed to be a potential strategy to improve physical stability over time.