Submitted to: Carbohydrate Polymers
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/10/2006
Publication Date: 1/2/2007
Citation: Stevenson, D.G., Biswas, A., Jane, J., Inglett, G.E. 2007. Changes in structure and properties of starch of four botanical sources dispersed in the ionic liquid, 1-butyl-3-methylimidazolium chloride. Carbohydrate Polymers. 67(1):21-31. Interpretive Summary: Starch lacks solubility in a wide range of solvents, with solvents that are effective often being hazardous. In this study we investigated the effectiveness of an ionic liquid, a rapidly growing group of chemicals that are environmentally friendly (green chemistry), to solubilize starch from corn, rice, wheat, and potato without altering starch structure and properties. Ionic liquid was effective in solubilizing starch from all four botanical sources but amylopectin molecules (the branched starch molecules) were degraded into 4-6 compounds for the cereal starches and two for potato. Ionic liquids can assist the starch industry in producing modified starches with significant reduction in environmental pollution.
Technical Abstract: Ionic liquid (IL) has gained industry attention, especially in green chemistry. Researchers have utilized IL for dispersing cellulose, but no report using IL for other polysaccharides. In this study, corn, rice, wheat and potato starches were dispersed in hot water (DIHW) or IL, 1-butyl-3-methylimidazolium chloride and morphology, amylopectin molecular weight (APMw) and thermal properties (TP) were analyzed. For starch DIHW, corn and potato had gelatinized aggregates, whereas rice and wheat had granular clumps. Starch heat-dispersed in IL (HDIIL) had clumps composed of < 1 micrometer diameter particles. Starch DIHW had little effect on APMw. Cereal starches had APMw greatly reduced by HDIIL (4-6 peaks observed). Potato amylopectin was degraded less by IL (two peaks) probably because negatively-charged phosphomonoesters covalently bonded to positively-charged imidazolium rings or repelled IL chloride ions, and large granule size of potato starch may have impeded IL penetration, reducing reaction efficiency. TP showed potato starch incompletely gelatinized by HDIIL.