Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 22, 1999
Publication Date: N/A
Interpretive Summary: Chemically modified starches have potential for numerous industrial applications if these could be made more rapidly and with fewer byproducts. Currently, most starch modifications are carried out in water which often reacts to form unwanted byproducts and large quantities of waste water. In this study, acetic acid, a relatively safe solvent, which should not form byproducts, was evaluated as a solvent for starch. It was found that starch-acetic acid mixtures will melt at temperatures of about 180 deg C. Once melted, it is expected that the starch will be much more reactive and will behave as a thick plastic type material. This information should be useful to scientists in academia and the starch industry who are attempting to prepare chemically modified starches in a more rapid and cleaner process.
Technical Abstract: Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) methods were used to determine if starch-glacial acetic acid mixtures can be melted and thermally processed at reasonable temperatures. DSC studies showed that the melting temperature of dry starch was reduced from about 280 deg. C to 180 deg C in the presence of >30% acetic acid. Glass transition temperatures varied from 110 to 40 deg C at 15 and 45% acetic acid, respectively. XRD showed the loss of native starch crystallinity and the formation of V-type complexes. Addition of 10% water decreased the melting temperatures to 140-150 deg C while addition of a base (sodium acetate) had little effect. Some possible applications of processing starch in non-aqueous solvents will be discussed.