Fabricating multilayer emulsions by using OSA starch and chitosan suitable for spray drying: Application in the encapsulation of β-carotene

The aim of the present study was to investigate the application of octenyl succinic anhydride (OSA) starch and chitosan to form multilayer nanoemulsions in the spray-drying microencapsulation of beta-carotene in oil. Initially, the single and bilayer nanoemulsions were prepared and optimized by varying their compositions with the characterization of mean particle diameter (MPD), polydispersity index (PDI) and zeta-potential (ZP). The optimized composition of the bilayer emulsion was 9 wt% medium chain triglycerides (MCT) oil phase, 4.6 wt% OSA starch and 0.3 wt% chitosan. The MPD, PDI and ZP of the bilayer emulsion were 183.6 +/- 0.7 nm, 0.17 +/- 0.03 and 24.9 +/- 1.9 mV, respectively. The stability of single and bilayer emulsions against acidic pH was evaluated. In the spray-drying process, the effects of OSA starch/maltodextrin as wall materials on the bilayer emulsion were investigated. Another complex interfacial layer with adjustable surface positive charges could be formed by mixing the bilayer emulsion with these wall materials. The spray-dried microencapsulated particles were characterized and the degradation of beta-carotene at different temperatures was studied. The stability of encapsulated beta-carotene was influenced by the different constituents at the oil in water interface and the multilayer interface was demonstrated to provide the best protection during storage. These results have important implications for the spray-drying microencapsulation of functional additives with OSA starch as both emulsifier and wall materials.