Steam jet cooking of high-amylose starch fatty acid mixtures. An investigation of complex formation

We have investigated the formation of helical inclusion complexes when aque ous mixtures of high-amylose starch and lauric, myristic, palmitic and stea ric acids are processed by steam jet cooking at 140 degrees C. The amount o f free fatty acid that complexes with amylose was compared with the amount complexed when the fatty acid was present in its water-dispersible, sodium salt form. Air-dried and finely-ground products prepared from lauric and my ristic acids and their sodium salts were extracted to remove uncomplexed fa tty acid. A quantitative Fourier transfrom infrared spectroscopic (FTIR) me thod, based upon absorption of the carboxylic acid carbonyl, was then devel oped to determine the amount of complexed fatty acid remaining in the produ ct. For both of these fatty acid systems, only small differences in complex formation were observed between the free acid and the sodium salt. Althoug h water solubility of these fatty acids is negligible at room temperature, solubility is apparently sufficient for complex formation under the high-te mperature, high-shear conditions of the steam jet cooking process. Products prepared from lauric, myristic, palmitic and stearic acids and their respe ctive sodium salts were also examined by X-ray diffraction. This technique confirmed the results obtained by FTIR and also showed that differences bet ween free acid and sodium salt become more pronounced as the fatty acid inc reases in molecular weight, and water solubility is reduced. For the steari c acid system, complexation of free acid was roughly half that observed wit h the sodium salt. (C) 1999 Elsevier Science Ltd. All rights reserved.