Effect of processing conditions on cell structure of starch-based foam

Abstract

In this work, the effects of processing conditions on the cell structure were studied for starch foam through investigating the effect of water content and processing temperature and shear stress on starch-based materials. It was found that there was a critical point of water content (between 16-18%) where expending ratio changed significantly since the cell structure changed from open to closed. The lower water content was, the higher Tm of starch-based materials was, which resulted in lower melting strength and open cell structure. Conversely, the higher water content and the lower Tm resulted in higher melting strength and closed cell structure. The closed cell structure prevented moisture evaporation during foaming and kept the lower Tm, which resulted in foam shrinking when the materials was cooled down since negative pressure in the cell. The higher temperature not only increased the steam pressure but also decreased the melt strength of starch-based materials, which enhanced the open cell structure.