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

摘要

The aim of the present work was the rheological and microstructural analysis of olive oil/mono- and diglycerides/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 degrees C/min) were adopted to evaluate the onset of crystallisation temperature (T_co) 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 T_co. Afterwards, the influence of mono- and diglycerides 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 T_co with its concentration from 17.7+or-2.7 degrees C up to 64.5+or-1.0 degrees C. Experimental results showed that T_co 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 fat 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 amounts of the organogelator and the saturated fats, respectively.