Highly stable spray dried tuna oil powders encapsulated in double shells of whey protein isolate-agar gum and gellan gum complex coacervates

This study was aimed at producing multi-core fish oil powders by developing a double-shelled microencapsulation system using complex coacervation. Whey protein isolate (WPI)-agar gum (WPI-AG) complex coacervates and WPI-gellan gum (WPI-GG) complex coacervates were used as the inner and outer shells, respectively. Tuna oil was used as a representative core material. The oil was first encapsulated in WPI-AG complex coacervates at pH 4.75 to produce the primary microcapsule. The second microcapsule shell was created by using WPI-GG complex coacervates at the same pH and mixed with the primary microcapsule, followed by the cooling to 15 °C in the presence of calcium ions. The WPI-GG outer shell was clearly visible under a light microscope. The outer shell significantly improved the oxidative stability of the entrapped tuna oil, compared with the microcapsule powder without the outer shell. These spray dried double-shell microcapsule powders had low surface oil (1.8%), high encapsulation efficiency (95.8%) and a high payload (42. 6%). These shells were glassy with glass transition temperature around 53 °C and they acted as effective barriers to transmission of oxygen at ambient temperature.