Effect of inclusion complex formation and mechanoactivation on the structure and rheological behavior of starch-oleic acid mixtures

Abstract

In the present work, for the first time, mechanical activation implemented in a rotor-stator device (RSD) has been used to enhance the formation of the amylоse-fatty acid complex in gelatinized starch at a moderate temperature (40 °C) using oleic acid (ОА) as a model guest compound. Mechanical activation was found to cause an increase in the complexing index from 10 to 30 % for non-activated mixtures to 83–92 %. The study of aqueous and dried starch-OA mixtures using optical and AFM microscopy and dynamic light scattering methods revealed a uniform distribution of amylose-OA complex particles with a size of 125–260 nm in the starch matrix. The freeze-dried starch-ОА sample prepared using mechanical activation exhibited a V-type crystalline structure. By rotational viscometry and dynamic rheometry, it was found that mechanical activation causes the gelation of aqueous starch-OA mixtures, which accompanies a decrease in their fluidity and an increase in elasticity. The developed method can be recommended for large-scale production of thickening and texture modifying materials based on gelatinised starch containing a fatty acid as a nutritional or structuring additive.