Free-solvent synthesis and properties of higher fatty esters of starch - Part 2

A solvent-free synthesis and the properties of esters of starch from differ ent sources (maize, waxy maize, Eurylon 7, potato, wheat, rice, amy lose, a nd amylopectin) and higher fatty acids are described. Higher fatty acid est ers (C-8-C-18) of potato starch were synthesized by chemical gelatinization using formic acid, followed by treatment with fatty acid chlorides. Esteri fication was readily carried our at 105 degrees C and a reaction time of 40 min. Formic acid permits esterification of starch by long-chain acid chlor ides with minimum degradation. The results indicated that the degree of sub stitution of the starch esters diminishes with increase in fatty acid chain length. All starch eaters have a hydrophobic character which rises with le ngth of the Fatty side chain. X-ray and Differential Scanning Calorimetry ( DSC) showed that the fatty acid side chains (C-n > 16)grafted onto starch f orm cristallites between them. This phenomenon provokes the decrease of elo ngation at break for these starch esters. On the other hand, the tensile st rength at break and thermal stability of fatty esters of starch increase bo th with a higher fatty chain grafted onto starch.