Papers by Author: J. Bon

Abstract: Grape pomace is the main by-product from the wine industry. It is principally made up of grape skin and seeds. Drying this by-product is the first step for the later extraction of components with high added value like oil or antioxidants. Due to the different characteristics of the components, the study of the drying kinetics of grape pomace must be addressed taking its components into account one by one. For that purpose, grape seeds from the Spanish wine industry were dehydrated in a convective laboratory dryer at 70 °C and at 1, 2 and 3 m/s until a weight loss of 40% was reached. Drying kinetics was determined in triplicate. Modelling was carried out by means of a diffusion model without considering shrinkage and external resistance. Grape seeds were assumed to be spherical. For all the fits, the explained variance was higher than 96.9 % and the mean relative modulus was lower than 1.7 %. Between 1 and 2 m/s, effective diffusivity increased in line with air velocity, although the values of effective diffusivity calculated for 2 and 3 m/s were similar. It seems to indicate that for the experimental conditions under study, the external resistance is not negligible at 1 and 2 m/s and for higher air velocities the internal resistance to mass transfer controls the drying process. These results coincide with those found by other authors when studying different food products.

Abstract: Intermittent drying is an alternative technology to continuous drying that improves the product quality as result of diminishing the average material temperature and the heating time. In this study, the application of the intermittent drying technology to mango drying (Mangifera indica L.) was analyzed and optimized. To formulate the optimization problem, an objective function was proposed in order to improve the product quality and decrease the energy consumption. To quantify the objective function, a mathematical model for a cubic shape was formulated and validated, considering diffusional mass and heat transfer with non-negligible external resistances.

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.