Influence of different combinations of wall materials and homogenisation pressure on the microencapsulation of green coffee oil by spray drying

Abstract

The aim of this study was to assess the influence of different combinations of modified starches (Hi-Cap, Capsul and N-Lok) or gum Arabic with maltodextrin 10 DE (MD) (75:25), on microencapsulation of green coffee oil by spray drying and two homogenisation processes on emulsion preparation step. All emulsions were evaluated for droplet size, viscosity, zeta potential and surface tension, while microparticles were analysed for encapsulation efficiency, oil retention, moisture content, particle mean diameter, microstructure, in vitro sun protection factor and oxidative stability by Rancimat. Critical storage conditions based on sorption isotherms and glass transition temperature and diterpenes quantification were determined for the microparticles with the highest values of encapsulation efficiency. In general, the use of 50MPa of homogenisation pressure allowed a reduction of droplet mean diameter for about 1μm, with a slight decrease on emulsion viscosity. For microparticles, there was an increase on encapsulation efficiency with the use of high pressure homogenisation. Oil retention was influenced by the type of wall material. Moisture content (2.0%) and in vitro sun protection factor values (FPS=2.1) were similar for all emulsions and in the last case were similar to pure oil. Particle mean diameter ranged from 10.7 to 16.0μm. Powders produced with the mixture Hi-Cap/MD presented good values of critical water activity of 0.60 and critical moisture content of 0.08g/g of dry solids, respectively, and also the highest oxidative stability. High concentration of diterpenes of 0.21 and 0.24mg of kahweol/g powder, 0.19 and 0.21mg of cafestol/g powder were observed for particles produced with Hi-Cap/MD and GA/MD, with emulsions homogenised at 50MPa.