Production of recrystallized starch microspheres using water-in-water emulsion and multiple recycling of polyethylene glycol solution

Recrystallized starch microspheres (RSMs) were prepared by using water-in-water emulsion method. Polyethylene glycol (PEG) solution was used as the continuous phase. To enhance the cost-effectiveness of this method, PEG was recovered and reused. The recovered PEG was used without (DR-PEG) and with supplementing with fresh PEG (RS-PEG). An exponential concentration-apparent viscosity relationship (R2 = 0.99) of PEG solution was used to calculate the concentration of recovered PEG solution. When the DR-PEG solution was used, the yield of RSMs decreased 0.7%-11.9% as the recycle number increased. The clumping of microspheres was observed in the first and second recycles. When the RS-PEG solution was used, the yield of RSMs continuously increased from 78.2% to above 83.0% and the desirable features of the RSMs including spherical shape, well-dispersed nature and well-organized crystalline structure remained unchanged up to 5 recycles. These findings will enable production of RSMs in more cost-effective way and help minimize the waste of PEG.