Assessment of the protective potential of coated microparticles in a fluidized bed against the simulated digestion

A strategy to enhance the protective effect of bioactive compounds in spray-dried microparticles is fluidized bed coating. Linseed oil was previously microencapsulated by spray drying using maltodextrin and whey protein as wall materials, and then coated with hydroxypropyl methylcellulose using a fluidized bed. A central composite rotatable design was used to assess the effects of coating solution flow rate (Q) and fluidizing air temperature (T) on the surface oil content and water activity of the coated microparticles. Under optimal conditions (Q = 1.87 mL/min and T = 71 °C), the surface oil content and water activity were 10.4 % and 0.484, respectively. Raman spectroscopy analysis revealed the predominance of wall material peaks in the product spectrum, with attenuation of the linseed oil peaks. Visually, micrographs from fluorescence microscopy suggested homogeneous deposition of the coating material on the surface. The barrier properties of the additional layers against in vitro digestion were evaluated. Regarding simulated digestion, the uncoated material showed a high free fatty acid release rate in the first 30 min of digestion, whereas the coated material showed a reduced lipolysis rate. The maximum release for the coated and uncoated particles was 22.38 and 48.14 %, respectively. Coating with HPMC can form an additional physical barrier, enhance system viscosity, adsorb onto the oil droplet interface, provide steric hindrance, and flocculation depletion, thereby limiting lipase activity. Optimized coated microparticles can be used in special low-calorie diets because of their low release of free fatty acids.