Pea (Pisum sativum, L.) Protein Isolate Stabilized Emulsions: A Novel System for Microencapsulation of Lipophilic Ingredients by Spray Drying

Oil-in-water emulsions can be considered as an important delivery system for lipophilic food molecules. In this study, pea protein isolate (PPI) was studied for its emulsifying capacity at various pH values and pH 7 was selected to prepare emulsions for the production of dry microcapsules. Emulsions stabilized by PPI just enough to cover oil droplets were mixed with solutions of starch hydrolysates of various dextrose equivalent (DE) and subsequently spray dried to yield powders with 30 wt% oil. Effects of DE (6, 12, 19, and 28) on feed emulsion properties and on the characteristics of the spray-dried powders were examined. Reconstituted emulsion oil droplet size and stability were affected by DE in all cases. Microencapsulation efficiency of dried emulsions increased significantly with increasing DE. The scanning electron microscope results showed that lower maltodextrins DE microcapsules are shallow and presented rough surfaces or invaginations. However, higher carbohydrates DE microcapsules were circular and uniform showing minimum cracks and dents on the surface confirming these DE to be efficient encapsulating materials. The formation of the drying matrix seems control the destabilization of pea protein-coated oil droplets during spray drying. In systems where the matrix is formed in a uniform manner, the interfacial protein film is less affected by the drying process. Thus the functionalities of pea protein can be protected during drying by using high DE carbohydrates.