MODIFICATION OF NATURAL POLYMERS BY THERMO-MECHANICAL PROCESSING
Location: Plant Polymer Research
Title: Ionic Liquid as a Solvent and Catalyst for Acylation of Maltodextrin
Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 12, 2009
Publication Date: July 1, 2009
Citation: Biswas, A., Shogren, R.L., Willett, J.L. 2009. Ionic Liquid as a Solvent and Catalyst for Acylation of Maltodextrin. Industrial Crops and Products. 30(1):172-175.
Interpretive Summary: Among the industrial materials, starch is one of the cheapest and most cost-effective. In addition to being a major food item, it is currently used industrially as coatings and sizing in paper, textiles and carpets, as binders and adhesives, as absorbants, and as encapsulants. Hydrolysis of starch produces a group of low-molecular-weight carbohydrates named dextrins. Dextrins are mixtures of linear alpha-(1,4)-linked D-glucose polymers. They have the same general formula as carbohydrates but are of shorter chain length. Dextrins find widespread use in industry, due to their non-toxicity and their low price. They are used as water soluble glues, as thickening agents in food processing, and as binding agent in pharmaceuticals. In pyrotechnics they are added to colored fire formulas, allowing them to solidify as pellets or "stars." Cyclodextrins find additional use in analytical chemistry as a matrix for the separation of hydrophobic substances, and as excipients in pharmaceutical formulations. Not all forms of dextrin are digestible, and indigestible dextrin is sometimes used in fiber supplements. For example, maltodextrin is a moderately sweet polysaccharide used as a food additive. In the United States this starch is usually corn or potato, elsewhere such as in Europe it is commonly wheat and is usually found as a creamy white hygroscopic powder. Maltodextrin is easily digestible, being absorbed as rapidly as glucose. In this work, we found an inert solvent for maltodextrins that also catalyzed the esterification reaction with vinyl esters. This would enable us to improve the starch or dextrin properties by modifying those with many reactants that would have been impossible otherwise. This study has shown that starch stearates of a range of DS and solubilities can be prepared simply by heating starch, ionic liquid bmim[dca] and vinyl stearate or stearic acid. We developed a method to prepare starch acetate by the use of cheap stearic acid rather than the much more expensive vinyl stearate. Our methodology may help making such novel starch esters more practical as previous methods to starch stearate have required the use of vinyl stearate as well as a harsh chemical or enzymatic catalyst. Some applications for these materials may include coatings, emulsifiers, dispersing agents and nanoparticles.
Catalyst-free esterification of maltodextrin was carried out in ionic liquid. Stearate esters of maltodextrin were obtained in various degree of substitution (DS) when vinyl stearate or stearic acid was heated with maltodextrin in ionic liquid, 1-butyl-3-methylimidazolium cyanamide (bmim[dca]). Reaction temperatures of 75 degrees C gave the highest values of DS (0.64) and reaction efficiency (64%). Structure and DS of the resulting esters were confirmed by NMR, titration, GC, and elemental analysis. It was found that for some of the maltodextrin stearates the mixed solvent of chloroform/DMSO (70/30) was better than DMSO.