Novel Composite Microparticles of Alginate Coated with Chitosan for Controlled Release and Protection of Ascorbic Acid

Novel composite microparticles of alginate (ALG) coated with chitosan (CS) were prepared via ionotropic/external gelation technique for controlled release and protection of ascorbic acid (AA), a strong antioxidant. The microparticles were characterized by Fourier transform infrared, X-ray diffraction, and scanning electron microscopy. The encapsulation efficiency and loading capacity were 89.94 +/- 5.62% and 37.01 +/- 1.83%, respectively. The degree of swelling of the microparticles at pH7 was much higher than that at pH2.0. The release profiles showed that AA could be slowly released from microparticles and polymeric relaxation was the prevailing release mechanism. The ALG/CS microparticles exhibited protective effect on AA against light and heat exposure degradation. After 7days of ultraviolet exposure and 80 degrees C heating, the residual rates of AA in AA-loaded microparticles were 90.31% and 83.32%, which were much higher than 15.72% and 19.95% for free AA. The results suggested that the ALG/CS microparticles can be used as a reliable delivery system for AA.