Identification of key factors determining the surface oil concentration of encapsulated lipid particles produced by spray drying

Potential factors leading to surface oil were investigated by analyzing the impact of emulsion properties, atomization and drying conditions separately. An increased oil load, droplet size and in particular the size of droplet aggregates led to significant more surface oil. Increasing the viscosity, inlet temperature and relative humidity resulted in larger particles with a higher encapsulation efficiency. The results indicate that the probability of oil droplets being in contact with the particle surface determines the amount of surface oil. Oil diffusion towards the surface was excluded due to the short residence times and high viscosities. Keywords: microencapsulation; encapsulation efficiency; emulsion properties; atomization; drying conditions