Self-assembly in vegetable oils of ionic gelators derived from (r)-12-hydroxystearic acid

Publication date: Available online 25 July 2016 Source:Food Structure Author(s): Flor M. Alvarez-Mitre, V. Ajay Mallia, Richard G. Weiss, Miriam A. Charó-Alonso, Jorge F. Toro-Vazquez We investigated the self-assembly mechanism of N-alkyl-(R)-12-hydroxyoctadecylammonium chlorides (n-HOA-Cl; n = 3, 4, 6, and 18) during the development of organogels (5wt%) in safflower oil. The n-HOA-Cl are ionic gelators derived from the 12-hydroxystearic acid, some capable of forming both hydro- and organo-gels (i.e., ambidextrous). The results showed that self-assembly of the n-HOA-Cl resulted from a balance between electrostatic and London dispersion forces. During cooling the n-HOA-Cl self-assembled, initially, through electrostatic interactions between the protonated nitrogen atoms and the chloride counter ions of molecule pairs giving rise to an exotherm (TCr1). Further cooling resulted in a second exotherm (TCr2) associated with the crystallization of the n-alkyl chains. After achieving 10°C all the n-HOA-Cl organogels showed low viscoelasticity (100Pa to 5000Pa). However, under isothermal conditions at temperatures between TCr1 and TCr2, the 4-HOA-Cl (i.e., at 113°C or 106°C) and 6-HOA-Cl (i.e., at 102°C) undergo a morphological transition from microplatelets to spherulites. In the case of 4-HOA-Cl this transition resulted in organogels with higher rheological properties (≈ 10,000Pa) and melting temperature (125°C to 145°C) than any of the other n-HOA-Cl organogels form...
Source: Food Structure - Category: Food Science Source Type: research