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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 ºC 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.

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.

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.

Shrinkage of potato cubes, parallelepipeds and cylinders was addressed during drying. A basic methodology by using image analysis was set-up in order to measure and monitor geometrical changes along the drying process. Both measurements by image analysis and directly with a calliper were carried out. Results from both methods showed a good agreement with no bias. Particle shape was found to influence shrinkage in a different way according to the axis. In fact the larger dimension shrinks less than the shorter one. This could be linked to the influence of the core drying in shrinkage. Experiments were also carried out for cauliflower stems. The difference in shrinkage between directions was greater for cauliflowers, due probably to the effect of alignment of fibers along the axis. Good agreement with existing data in the literature for specific volume was found.

This paper is a contribution to the programme to classify finite distance-transitive graphs and their automorphism groups. We classify pairs (Γ,G) where Γ is a graph andGis an automorphism group of Γ acting distance-transitively and primitively on the vertex set of Γ, subject to the condition that there is a normal elementary abelian subgroupVinGwhich acts regularly on the vertex set of Γ and the stabilizerG0of a vertex (which is a complement toVinG) has a unique non-abelian composition factor isomorphic to one of the 26 sporadic simple groups. There are exactly 10 examples of Γ, all known for a long time.

Ultrasonic applications can be classified into low intensityor high intensityapplications. The latter are used to modify a process or product with ultrasonics, while in low intensityapplications the process or product modifies the ultrasonic signal, thus providing information about the product. Low inten sity ultrasonics in food technology can be used to monitor a process (liquid level, flowmeters) or to determine the quality of food products. Since ultrasonic techniques are rapid, non-destructive, easy to automate and relatively inexpensive, the number of applications is rapidly growing in this field. Ultrasonics can also be considered for use in laboratory testing devices to determine physical and chemical properties of foods. Ultrasonics has been used to determine texture, composition and physical state in liquid and solid foods. The commonly measured ultrasonic parameters are velocity, attenua tion and frequency spectrum composition. Velocity is the parameter used most since it is the simplest and most reliable measurement. This paper reviews the basic principles of ultrasonics, the most suit able techniques for each type of application, the testing devices needed to make measurements and the most interesting applications.

Abstract:  Mass transfer in highly porous and hemispherically shaped bodies was approached using a diffusional model. The drying kinetics of broccoli florets were investigated and the influence of air velocity and temperature determined. A threshold air velocity of 2.5 m/s was established over which no increase in the drying rate was observed, indicating that internal resistance controls mass transfer at higher velocities. The influence of temperature on drying was interpreted by the Arrhenius relationship. The activation energy obtained was 18.5 kJ/mol.

In this work is proposed the application of the ProSim process simulator for the analysis of wine aroma concentration by performing a two-level simulation: First, ProSim is used to attain a preliminary design of a distillation tower, and afterward the simulator is employed to analyze the behavior of the tower in a more precise way. The UNIFAC model was used for nonideal behavior description of the mixtures. In this application, the concentration of a 13-compound mixture was simulated. In fact, the numerical methods implemented in ProSim made it possible to attain the convergence quickly even with minor compounds. The results obtained showed that the use of ProSim results to be very advantageous because it is timesaving and improvements are attained with respect to the specific programs developed by researchers.

The optimal design of a convective drier is hereby considered by means of using a well-known spreadsheet: Microsoft Excel 5. OTm.The degree of freedom analysis enabled a non linear equations system to be set up, in such a way that it was possible for different design variables to be considered. The equations system was keyed in to provide a possible solution via the iterative procedure built in the spreadsheet. Other complementary variables were computed to provide a unit cost for the operation, thus occasioning the opportunity of considering an economic objective function.Constraint and design variables were identified in the program. By giving initial values to the design variables, and by using the optimization capabilities included in Microsoft Excel 5.0Tm, an optimal set of values for the design variables was determined.Finally, the influence of constraint and design variables was analyzed, where both the input air temperature and the relative humidity of exhaust air were binding factors.