Effect of oxidized sucrose, citric acid crosslinking and dual modification on some physicochemical properties of cassava starch for potential application in packaging films

Abstract

Background: Crosslinking is one method of starch modification that has been applied to improve the properties of starch and starch-based films. The effects of different crosslinkers on some properties of starch give an insight into the impact the crosslinking modification will have on the final behaviour of starch films. The aim of this study was to analyse the effects of oxidized sucrose and citric acid crosslinking on cassava starch intended for packaging film applications. Methods: Cassava starch was crosslinked with oxidized sucrose and citric acid individually and also in combination (dual modification). The properties studied were amylose content, degree of substitution (DS), degree of crosslinking (DC), solubility, swelling power and paste clarity while FTIR, SEM, XRD and thermal analysis were also carried out. Results: The optimal concentrations of oxidized sucrose and citric acid in this study were 1% and 5% resulting in a maximum amylose content of 20.78 and 19.4 respectively while an intermediate DS (0.182- 0.401) was recorded for all crosslinked starches. The swelling power and solubility of oxidized sucrose crosslinked starch (OS-starch) was lower than that of citric acid crosslinked starch (CA-starch) in all the temperatures observed. The SEM, XRD as well as FTIR analysis highlighted changes in the crystalline structure of starch granules after the crosslinking. Thermo-gravimetric analysis indicated that the thermal stability of all starches was significantly improved by crosslinking, as residual weights of 18.74%, 19.59% and 19.68% were observed for CA-starch, OS-starch, and dual modified starch (OS-CA starch) respectively. Conclusion: Overall, the study suggests that although both crosslinkers significantly improved the physicochemical properties of cassava starch studied, oxidized sucrose had higher effect on most these properties, hence can be suggested to be better suitable when modifying starch for packaging film applications.