Microencapsulation of fish oil by freeze-drying techniques and influence of process parameters on oxidative stability during storage

Dried microencapsulated fish oils (DMFO) were obtained by freeze-drying and the influence of various process parameters on oxidative stability was evaluated. Standard emulsions were composed of sandeel oil, sodium caseinate and lactose, homogenised by three passes at 40 MPa, frozen at -40 degrees C, kept at -30 degrees C and freeze-dried. In selected trials, carbohydrate, homogenisation pressure, freezing rate and initial temperature for freeze-drying were varied. DMFOs were stored at 25 degrees C in the dark and oxidation monitored through anisidine values and polymer levels. Results showed no apparent relationships between oil globule size or microencapsulation efficiency and storage stability, and the only trial with significantly longer shelf-life involved fast-freezing in liquid nitrogen.