Nano-morphological Modification of Amylose Biopolymer with Hydrocolloids for low Humidity and thin Film Applications

Abstract

Nano-structural modification without the presence of phase-separation interface is a novel way of improving and controlling the morphology and properties of biopolymers. Since biopolymers such as amylose show varied reactivity to humidity, new nanostructure can be formed by including hydrophilic molecules that interact within the same phase of matrix. Long chain amy lose re-crystallisation is an important equilibrating process leading to polymeric aging in biopolymer starch and anisotropic properties of starch polymeric films. Investigations into a number of plasticisers and hydrocolloids showed that their water retentionlbinding capability influence the starch polymer's crystallinity. New nano-morphology within the starch biopolymer can be achieved with up to 8 wt% glycerol and xylitol addition. Hydrocolloids such as xanthan gum reduced matrix elongation but their XRD analysis showed that sample crystallinity did not correlate with their respective tensile properties. Maltodextrin was ineffective in increasing degree of elongation even at 15 wt% addition rate, due to formation of pockets of larger nano-structured regions with higher crystalline domains. Both xylitol and xanthan gum samples showed similar tensile strength and elongation properties, but at high additive concentrations, the water retention capability of xylitol mixed amylose samples were about 27% lower than xanthan gum samples, respectively.