Effect of organogelator and fat source on rheological properties of olive oil-based organogels

Different samples of olive oil-based organogels were prepared by using cocoa butter, a vegetal fat rich in natural saturated components, and monoglycerides of fatty acids as an organogelator agent. Dynamic temperature ramp tests, carried out at 5 °C/min, allowed the determination of rheological characteristics (complex modulus, G*, and phase angle, δ) and onset of crystallisation (Tco) of the investigated materials. Experimental results showed that, at a Myverol amount less than 2% (w/w), Tco increases with the amount of saturated components in the fat mixture, whereas, increasing the organogelator fraction, Tco is only dependent on organogelator concentration. Moreover, a gelation temperature, Tg, corresponding to the dynamic moduli crossover, was observed for all samples with a Myverol content higher than 1.5% (w/w) and it was found to overlap with Tco when a critical concentration (ranging approximately between 2.3% and 3%) of the organogelator was exceeded. Rheological parameters are always affected by both oil phase composition and Myverol fraction; G* increases with either Myverol or cocoa butter amount, while the phase angle decreases, evidencing an increase in structure and consistency. The experimental results can be useful to design novel fat systems having the desired macroscopic properties: in fact crystallisation temperature can be set controlling the organogelator concentration whereas dynamic moduli can be properly changed by modifying the saturated-to-unsaturated fatty acids ratio.