Abstract
Modified starches offer a biodegradable, readily available, and cost-effective alternative to petroleum-based products. The reaction of alkenylsuccinic anhydrides (ASAs), in particular, is an efficient method to produce amphiphilic starches with numerous applications in different areas. While ASAs are typically derived from petroleum sources, maleated soybean oil can also be used in an effort to produce materials from renewable sources. The reaction of gelatinized waxy maize starch with octenylsuccinic anhydride (OSA), dodecenylsuccinic anhydride (DDSA), a maleated fatty acid (TENAX 2010), phthalic anhydride (PA), 1,2,4-benzenetricarboxylic acid anhydride (trimellitic anhydride, TMA), and three maleated soybean oil samples, was investigated under different conditions. To minimize the reaction time and the amount of water required, the outcome of the esterification reaction was compared for starch dispersions in benchtop dispersed reactions, for starch melts in a heated torque rheometer, and for reactive extrusion in a pilot plant scale twin-screw extruder. The extent of reaction was quantified by 1H NMR analysis, and changes in molecular weight and diameter were monitored by gel permeation chromatography (GPC) analysis. The outcome of the reactions varied markedly in terms of reaction efficiency (RE), molecular weight distribution, and average hydrodynamic diameter, for the products derived from the different maleated reagents used, as well as for the different reaction protocols.
Highlights
Starch is a biopolymer that is renewable, readily available, biodegradable and costeffective [1]
After 14 h, the reaction was neutralized with hydrochloric acid (HCl) to reach a final pH of 7.0, and the solid product was collected by gravity filtration and washed with either water or ethanol
The longer the chain length, the more hydrophobic the anhydride, which makes this process more difficult. One solution to this problem is to use gelatinized starch, so that the amylose and amylopectin molecules are free in solution and able to react with the anhydride [33]
Summary
Starch is a biopolymer that is renewable, readily available, biodegradable and costeffective [1]. These attributes make it attractive for food, and as a feedstock for industrial applications [2]. Starch is biosynthesized as two different macromolecules, namely amylose and amylopectin [4]. Amylose (Figure 1A) is an essentially linear molecule composed of glucopyranose (GPy) units connected by α-1,4 glycosidic linkages [5,6]. Amylopectin (Figure 1B) incorporates GPy units connected by α-1,4 glycosidic linkages [7], and branching introduced through α-1,6 linkages [8]. The proportions of amylose and amylopectin vary with the plant species [9], while some mutant plant strains are enriched in amylose or amylopectin, such as waxy maize starch containing > 99% amylopectin [10]
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