The influence of heat transfer on pore architecture of starch sponges during freeze-drying process

Utilizing starch with the characteristics of good biocompatibility, good biodegradable, promoting wound healing and styptic function, its sponges prepared have broad marketing prospects. The casting/lyophilization technology has been developed in this study to fabricate highly porous starch sponges. The gelatinized starch was frozen in a metal vessel and freeze-dried to form a highly porous sponge whose pores retain the shape of the ice crystals during freezing. Knowing that the water in the gelatinized starch would form ice crystals if frozen and that different freezing conditions may dramatically influence the pore architecture, the speed and direction of the heat transfer in freezing gelatinized starch were studied with regard to pore size and orientation. The lower temperature materials were frozen before drying, the smaller pore diameter and lower interval porosity they had. It also has been found that the pore size, orientation, and uniformity are significantly affected by condition of heat transfer during freezing.