Abstract: Sodium alginate (SA) microspheres that are used for L-ascorbic acid encapsulation were prepared by emulsification/internal gelation method.The optimized preparation conditions were studied by combination of single factor experiment and response surface method with encapsulation extent (EE) and particle sizes as indices and the conditions were identified as:dosage of Span 80,2% (mass of the oil phase material);volume fraction of water,30%;stirring speed,400 r·min^-1;mass concentration of SA,18.80 g·L^-1;mole ratio,n(acetic acid)/n(CaCO₃)=3.29;mass ratio,m(Ca)/m(SA)=0.071 6.Under these conditions,the EE of SA microspheres achieves 63.83%.To improve the EE further,microspheres were prepared using SA/N,O-carboxymethyl chitosan (NOCC) as wall materials under the optimized preparation conditions.The EE of SA/NOCC microspheres achieves 77.08%.The scanning electron microscope revealed that microspheres prepared with SA/NOCC have obviously less pores on the surface than that prepared with SA.

Key words: additive of cosmetics, L-ascorbic acid, sodium alginate, N,O-carboxymethyl chitosan, encapsulation extent, response surface method