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 eva luated. Standard emulsions were composed of sandeel oil, sodium caseinate a nd 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-d rying were varied. DMFOs were stored at 25 degrees C in the dark and oxidat ion monitored through anisidine values and polymer levels. Results showed n o apparent relationships between oil globule size or microencapsulation eff iciency and storage stability, and the only trial with significantly longer shelf-life involved fast-freezing in liquid nitrogen.