The encapsulation of organic liquids in polyurethane nanocapsules by interfacial miniemulsion polycondensation of isophorone diisocyanate and propanetriol has been performed. The influence of type and amount of encapsulated organic liquid has been studied and it was found that the encapsulation efficiency is dependent on the water solubility of the organic liquids, their interfacial tension against water and their compatibility with polyurethane. It was also shown how different types of surfactants and variations in pH and ionic strength of the continuous phase affected the stability during polymerization and the diameter of the miniemulsion droplets and the resulting nanocapsules. The long-chained anionic surfactant Disponil FES77 can be utilized over a larger pH range than SDS due to the contribution of steric stabilization. Relatively narrow size distributions were obtained.

Most liquid food flavours such as essential oils are volatile and prone to degradation in the presence of oxygen, light, moisture and high temperatures. Microencapsulation of volatile ingredients prior to use in food or beverages is a commonly used process to limit loss and degradation of flavours and aromas during processing and storage. Here, peppermint essential oil was microencapsulated via complex coacervation using a combination of bovine serum albumin and gum Acacia as wall materials. The resulting core-shell microcapsules were chemically crosslinked with a modified food-grade starch, and subsequently spray dried, resulting in dry microcapsules which could be easily redispersed in aqueous solutions. Microcapsule formation and stability, as well as microencapsulation yield of peppermint oil, were investigated as a function of polymer concentration, core material load/wall thickness and crosslinker concentration. The crosslinked peppermint oil microcapsules were spherical and mononuclear both before and after spray drying and redispersion, whereas control coacervate samples without crosslinker did not withstand the spray drying process. Microencapsulation yield as analysed by GC-MS showed no loss of peppermint oil during or after complex coacervation, and 54% loss after spray drying for the best combination of Polymer:Oil ratio and crosslinker concentration used here, indicating good overall protection of the core material.