Papers by Author: Carmen Rosselló

Abstract: The olive crop has a great importance in the economy of Spain. Every year during the pruning of the olive trees a significant quantity of leaves are cut and discarded. It is known that these leaves constitute a source of antioxidant compounds and its processing would provide an added value to this raw material. Antioxidant compounds may be damaged when drying, the previous process to extraction. Thus, the goal of this work was to study the influence of the high intensity ultrasound applied during the drying of olive leaves on the kinetic of extraction of antioxidants compounds. From the parameters identified from Naik model, it can be concluded that the application of high intensity ultrasound during drying reduced the antioxidant activity of extracts at the equilibrium but increased the initial extraction kinetic compared to conventional hot air drying. This last aspect could have high interest to the antioxidant extraction from an industrial scale point of view.

Abstract: Ultrasounds are mechanical waves that produce different effects when travelling through a medium, some related to mass transfer (i.e. microstirring at the interface, the so called "sponge effect" and cavitations). Thus, ultrasound appears to be a way to reduce both the internal and external resistances in osmotic food drying processes. In this study, the influence of the ultrasounds on water and solute transports during osmotic processes of drying is evaluated. Two different systems have been studied, apple slabs immersed in 30ºBrix sucrose solution, and pork loin slabs in sodium chloride saturated brine. The mathematical modelling of the mass transfers has been carried out by assuming diffusional mechanism and considering the mutual effect between the two mass transfers, the water losses and solute gains. The mass transfer curves in the osmotic process of apple drying in sucrose solution were satisfactorily simulated by using a diffusional model considering independent mass fluxes. Nevertheless, this model did not allow for the accurate simulation of the water losses in the system constituted by pork-loin in saline solution. When the mass fluxes were considered mutually affected, the simulation was accurate for both cases water and solute transfer.

Abstract: Drying kinetics of carrot cubes were carried out at 1 m/s air velocity at different air drying temperatures (30, 40, 50, 60 and 70±0.1 °C) (AIR experiments), and also at the same experimental conditions but applying high power ultrasound (US experiments). Two kind of diffusion models were used to simulate the drying kinetics, according to external resistance to mass transfer being considered (ER model) or neglected (NER model) for solving the diffusion equation. Diffusion ER model was solved using a finite difference method. Drying rate increased as air temperature was higher. Ultrasound also increased drying rate at the different temperatures, but the improvement on drying rate decreased at high temperatures, and almost disappeared at 70 °C. Effective moisture diffusivities only showed an Arrhenius type relationship with temperature for AIR experiments. The NER diffusion model was not accurate to simulate the drying kinetics at any experimental conditions tested. However, diffusion ER model provided a high closeness between experimental and calculated drying data (VAR>99.80). Through the parameters identified of the ER diffusion model, effective moisture diffusivity and mass transfer coefficient, the influence of the power ultrasound application on internal and external resistance to mass transfer was shown to be significant (p<0.05).