Physical Properties of Films Based on Gelatin and Dialdehyde Starch with Different Oxidation Degrees

Abstract

In this study, dialdehyde starch (DAS) was prepared by oxidizing corn starch using potassium periodateas the oxidant.The aldehyde contentsin DAS weredetermined using titration with hydroxylamine and were found proportional to the molar ratio of KIO4:C6H10O5.Fourier transform infrared spectroscopy was used to confirm the breakage of the bond between C2 and C3in anhydroglucose units and the formation of -CHO group in DAS. X-ray diffractometry showed a decrease in crystallinity of starch after periodate oxidation. Thermogravimetric analysis showed reduced thermal stability of DASin comparison with the native starch. The prepared DAS was blended with gelatin to form films by casting method. Increasing aldehyde contents in DAS from 0 to 12.2% resulted in decreased moisture contents, solubility in water, and the swelling capacity of gelatin-DAS films. The value of tensile strength and elongation at break of the gelatin-DAS films rose when the aldehyde content was low (0-3.5%), but declined when the aldehyde content was high (3.5-12.2%). Slight periodate oxidation is, therefore, an effective way to enhance the mechanical characteristics of blend films from DAS and other biopolymers.