Drastic difference in porous structure of calcium alginate microspheres prepared with fresh or hydrolyzed sodium alginate

► Calcium alginate microspheres were prepared by the SPG membrane emulsification technique. ► Nonporous and spherical microspheres were prepared with fresh sodium alginate polymers. ► Porous and spherical microspheres were prepared with 82-day-hydrolyzed sodium alginate polymers. ► The BET surface area of the microspheres prepared with 82-day-hydrolyzed sodium alginate was 6.5 times larger.