Development of ethyl cellulose shell-coated alginate droplets in w/o emulsions by electrospraying

Abstract: This research investigated the use of ethyl cellulose (EC) in w/o emulsions to stabilize dispersed aqueous alginate droplets in 0:100 or 90:10 (w/w) medium chain triglyceride (MCT):canola oil continuous phases. When the aqueous alginate solution (2 % w/w) was electrosprayed in the oil phases containing dissolved EC, a thin layer of EC shell was formed rapidly around hydrophilic alginate droplets, thereby stabilizing the dispersed phase. As EC concentration in the oil phases increased from 0.2 to 1.0 % (w/w), the interfacial tension value (determined from pendant drop tensiometry) increased from 7 to 11 mN/m for canola oil but decreased from 3.87 to 0.21 mN/m for MCT/canola oil blend. At 2 kV applied voltage, as EC increased from 0.2 to 1.0 % (w/w),the electrosprayed alginate droplet diameter decreased from 1600 to 2000 µm and from 1600 to 800 µm for canola and MCT/canola blend, respectively. At 7 kV, the droplet diameter decreased from 220 to 110 µm and from 160 to 70 µm for canola and MCT/canola blend, respectively. The changes in alginate particle size can be attributed to the process-dependent EC depletion rate in the continuous phases that altered the surface activity at the w/o interfaces. The emulsions prepared in MCT/canola blend were more stable than those prepared in canola oil. For example, at 1 % (w/w) EC and 7 kV, the w/o emulsion stored at 22 ^oC for 14 days resulted in 91 and 38 % (initial emulsion volume) settlement, for canola and MCT/canola, respectively. Overall, this study showed that EC is promising for forming an elastic shell on electrosprayed alginate droplets in w/o emulsion systems.