Structure and properties of compression-molded thermoplastic starch materials from normal and high-amylose maize starches

Abstract

ABSTRACT:The structural and mechanical properties of compression-molded normal and high-amylose maize starches were studied as a function of processing water content and ageing time. Rubbery thermoplastic starches were produced by compression molding of four maize starches with differences in amylose content and amylopectin structure. Glycerol (30% on the basis of dry starch) and water (between 10 and 35% on the basis of total mass) were used as plasticizers. After processing, the amorphous thermoplastic starch materials crystallized during ageing. The semicrystalline materials contained both E-type and V-type, as well as B-type crystallinity. The properties of the thermoplastic starch materials are dependent on water content during processing, starch source, and ageing time. The normal maize starch materials are highly flexible with elongations between 56 and 104%. The elongations of the high-amylose maize starch materials were between 5-35%. The tensile stress and E-modulus of the normal maize starch materials were in the range of 3.9-6.7 and 27-131 MPa, respectively. The tensile stress and E-modulus of the high-amylose maize starch materials increased from approximately 0.5 to 23 and 5 to 700 MPa, respectively, with increasing water content during processing from 10 to 35%. The differences in mechanical properties of the normal and high-amylose materials were explained by differences in the structure of the amylose and amylopectin structure. It was concluded that both lead to differences in the starch network.

Robust and Flexible Films from 100% Starch Cross-Linked by Biobased Disaccharide Derivative

“…For the thermogram of non-cross-linked starch, the melting peak was lost in broad decomposition peak. 31 The results were in accordance with the results reported by Liu et al 32 and Kumar et al 33 On the other hand, after cross-linking, the much higher decomposition temperature could be due to the more compact molecular structure and stronger intermolecular forces attributed to additional intraand intermolecular bonds formed due to cross-linking. Stability in Water.…”

Impact of Radiation Processing on Starch

“…In this regard, the past decade has witnessed development and restructuring to convert starch into a thermoplastic material (Kirby and others 1993;Lourdin and others 1995;Spence and others 1995;Van Soest and Borger 1997;Sen and Bhattacharya 2000;Gomes and others 2001). Plastic formulations comprising corn-based starch (6% to 50%), to enhance the susceptibility of plastic products to biological degradation, have also been reported others 1980, 1987).…”

Nanostructural Morphology of Plasticized Wheat Gluten and Modified Potato Starch Composites: Relationship to Mechanical and Barrier Properties

“…It has been reported that long linear glucans, like amylose molecules, tend to form more entanglements compared to highly branched amylopectin molecules. 15 Therefore, the long chained amylopectin starch used in the present study should act as a linear chain and have an influence on the chain entanglements development during extrusion. For bio-based materials it is of interest, from a techno-functional point of view, to explore a potato starch with amylopectin of longer chains length and decreased degree of branching as a good potential raw material for improved packaging materials.…”