Accelerated Stability Studies of Microencapsulated Anhydrous Milk Fat

The objective of this work was to investigate the physical and oxidative stability of encapsulated milkfat. A model system similar to non-dairy creamer was used with anhydrous milkfat instead of tropical oils. Spray dried emulsions were maintained at 25 °C and 43.7±2.6% relative humidity with and without UV acceleration. Surface and encapsulated fats were analysed for peroxide value, 18:2 and 18:3 fatty acid contents, and head space hexanal. Oil droplet size distribution and powder morphology were monitored. The surface fat in both control and UV exposed powder decreased in the first 24 h and remained constant thereafter. The encapsulated fat showed a slower weight reduction in the UV-treated samples, perhaps due to oxidation-induced polymerization which reduces lipid extractability. The surface fat in the UV-exposed powders oxidized far more rapidly than that in the encapsulated fat. Despite the large differences in oxidation between the control and the UV-exposed powders, no discernable change was observed in their physical properties. Either no physical change occurred because of hindered molecular mobility or, physical changes did occur but were not detected by the methodology used. Work is continuing to investigate this phenomenon.