Heat-sealing property of cassava starch film plasticized with glycerol and sorbitol

Here, we investigated the effects of plasticizers on the physicochemical properties, crystallinity, and heat sealability of cassava starch films. An increase in the content of sorbitol resulted in a decrease in the moisture content and thickness of the films. The elongation at break was much lower for the films with high sorbitol content than for those with high glycerol content, owing to the lower plasticizing effect of sorbitol derived from its structural similarity to starch. X-ray diffraction (XRD) analysis revealed a decrease in crystallinity with an increase in sorbitol content, indicating the association between the ratio of plasticizers and degree of crystallinity in the films. Higher sorbitol content led to higher seal strength due to the presence of more hydroxyl groups for interaction with polymer chains; however, it also caused high crystallinity and phase separation. Cross-sectional images of sealed films revealed incomplete sealing for films containing a high glycerol content. In conclusion, the plasticizer type and content are crucial factors for the heat sealing of cassava starch films.