Effect of shear rate on crystallisation phenomena in olive oil based organogels

The aim of the present work is the rheological and microstructural analysis of olive oil/mono- and di-glycerides/cocoa butter organogels as a potential oil phase of structured food emulsions. Step temperature ramp tests at different shear rates and controlled cooling conditions (5°C/min) were adopted to evaluate the onset of crystallisation temperature (Tco) and viscosity of different samples. In order to study the crystallisation phenomena potentially occurring in adopted raw materials, a preliminary characterisation was carried out on pure and blended fats (olive oil and/or cocoa butter), evidencing a relevant effect of adopted shear rate on Tco. Afterwards, the influence of mono- and di-glycerides on organogelation of either pure or blended fats was investigated increasing the organogelator from 0.5% (w/w) up to 60% (w/w) and observing the increase of Tco with its concentration from 17.7±2.7 °C up to 64.5±1.0 °C. Experimental results showed that Tco is only determined by the organogelator concentration, and it does not depend on the shear rate and fat source. On the other hand, sample viscosity depends on both the amount of organogelator and the oil phase composition, increasing with saturated fats concentration. Finally, the obtained results allow the fat to be designed with the desired properties: its crystallisation point and rheology can be predicted on the basis of the amount of organogelator and the saturated fats respectively.