Extractable oil in microcapsules prepared by spray-drying: Localisation, determination and impact on oxidative stability.

Aim of the present study was to investigate the localisation of the extractable oil in spray-dried microencapsulated fish oil prepared under different spray-drying conditions and to investigate the impact on lipid oxidation upon storage. Confocal laser scanning microscopy, scanning electron microscopy and different extraction procedures revealed that the extractable oil in microencapsulated fish oil is mainly located on the surface and in oil droplets close to the surface. Consequently, different methods for determination of the different fractions are proposed. Lipid oxidation as determined by hydroperoxide content or anisidine value was higher in microcapsules with 50% oil load spray-dried at 210/90°C, propanal content was increased in samples with 30% oil load spray-dried at 210/90°C. The differences in stability could only partly be explained by the varying amount of extractable oil. It is concluded that the surface oil protects other fractions of the extractable oil and that the extractable oil cannot be used to predict shelf-life of microencapsulated oils.