Facile Esterification of Degraded and Non-Degraded Starch

Jakob Konieczny, Katja Loos
2018 Macromolecular Chemistry and Physics  
thermoplasticity and water resistance to the modified starch over the unmodified one. Modified starch-based materials are used in industry as glues, adhesives, and auxiliaries of a wide range of rheological and functional properties. It was found that the properties of polysaccharide-based plastics are strongly dependent on the degree of modification as well as on the regioselectivity of the substitution. So far, sophisticated experimental techniques, solvents, or systems of solvents, were used
more » ... to achieve homogeneous modification of the chosen polysaccharide. However, these techniques are expensive, typically use toxic solvents in highly alkaline conditions at high temperatures, are not viable for the large-scale industrial production of modified starches, and/or bear health risks when utilized. Biswas et al. were able to show an elegant yet simple approach toward cellulose, starch, and other polysaccharides using acetic anhydride in the presence of a catalytic amount of iodine. [10] Iodine seems to be an excellent acylating reagent for both starch and cellulose as it activates the carbonyl group of acetic anhydride, making the latter more reactive toward the carbohydrates. This method was already used by several groups for very interesting cellulose modifications [11] [12] [13] and esterification of whole grain starches. [14] [15] [16] In our current work, we studied the feasibility of this procedure in more detail for the esterification (acetylation, propionation, and esterification with longer fatty acids) of white potato dextrins (AVEDEX W80) and "waxy potato" starch containing more than 95% amylopectin (ELIANE) [17] [18] [19] -both are commercial carbohydrates used in various applications from food to paints. [20, 21] Dextrins are frequently used in paper coatings as they readily form an adhesive paste when mixed with water. White dextrins, such as AVEDEX W80, are derived from starch by partial thermal degradation under acidic conditions. [22] The difference between white dextrins and other dextrins is that they can form a viscous paste in cold water, making them attractive for water-borne coatings. [23] ELIANE is a commercially available 100% amylopectin potato starch obtained via innovative classical breeding techniques. [24] Amylose has very low water solubility and amylose solutions are very unstable-amylopectin is highly soluble in water and forms stable solutions. ELIANE is therefore a very attractive high-molecular-weight [25] polysaccharide for stable high-content polysaccharide solutions and is at the moment mainly used in food applications. [26] Both used carbohydrates are (highly) branched and hold a high amount of functional groups per molecule, which is especially attractive for industrial purposes [27] offering a high functionality, broad variety of functional groups, high solubility, and a unique rheological behavior. [28, 29] The reported modification of these carbohydrates can be used to adjust their properties for specific Polysaccharide Modification The iodine-catalyzed esterification (acetylation and propionation) and esterification with longer fatty acids of white dextrins (degraded starches) and "waxy potato" starch containing more than 95% amylopectin are reported. The degree of substitution can be finely tuned by a simple variation of the catalyst versus the amount of anhydroglucose units. Longer fatty acids can be readily converted using 1-methylimidazole as a solvent. The esterified carbohydrates are attractive for industrial purposes, offering high functionality, a broad variety of functional groups, high solubility, and a unique rheological behavior.
doi:10.1002/macp.201800231 fatcat:5hcvyt6lh5aovboogat6jlnhmu