Guillermo H. Crapiste

Sorptional equilibrium and drying characteristics of garlic

Abstract Drying characteristics of garlic including moisture sorption equilibrium, drying kinetics and pungency losses were investigated. Adsorption and desorption isotherms at 25, 45 and 65 °C were determined and correlated with a four parameter equation. The influence of temperature on adsorption was negligible and some hysteresis effect was observed. Air drying experiments and a diffusive model taking into account the internal and external resistances to mass transfer were used to evaluate effective diffusivity and energy of activation for diffusion. The effective diffusivity increased with temperature, ranging from 1.54 to 3.45 10 −10 m 2 /s in the wet zone and from 0.34 to 0.58 10 −10 m 2 /s in the dry zone. The effect of air velocity, air relative humidity and sample thickness on drying kinetics was also studied. Changes in garlic flavor or pungency during dehydration as a function of temperature, based on determination of pyruvic acid, was measured and modeled as a first-order reaction. At higher temperatures the enzymatic pyruvic acid decreased faster than the total pyruvic acid.

Modelling the pneumatic drying of food particles

A one-dimensional model for pneumatic drying of food particles is presented. The model includes mass, momentum and energy transfer between the gas and the solid phases, taking into account variations of properties with humidity and temperature as well as solid shrinkage during drying. A plug-flow assumption is made for the dryer model and the non-spherical shape of particles is considered in drag and heat transfer coefficients. The set of coupled non-linear ordinary differential equations is solved numerically for the velocity, moisture and temperature of particles and air along the dryer. The model is applied to simulate the drying of potato particles under different conditions. Model predictions are used to illustrate the complex transport phenomena that occur during the process and the profiles of temperature, moisture content and pressure developed through the dryer. Effects of mass flowrates ratio, velocity and temperature of air, shape and size of particle on drying time and final moisture content of the material are studied.

Kinetics of the Hydrogenation of Sunflower Oil over Alumina Supported Palladium Catalyst

The present work studies the sunflower oil hydrogenation on supported palladium catalysts, by analyzing the surface kinetics and the mass transfer limitations of products and reactants. Initially, a simplified model was studied. This model took into account only the consecutive hydrogenation of linoleic acid (diene), to reach the production of oleic (monoene) and stearic (saturated) acids. Using the adjusted values of the kinetic constants and the activation energies of the hydrogenation obtained with this model, a new scheme was investigated considering the geometric isomerization reactions (cis-trans). The diene hydrogenation constant was larger than that of the monoene. This fact confirms the higher reaction rate of the diene hydrogenation in comparison with that of the monoene. With respect to the isomerization rates, these have an activation energy superior to that of the monoene hydrogenation, and slightly superior to the diene hydrogenation activation energy. This fact verifies the influence of temperature on the formation of trans-isomers.

Modeling and simulation of an oilseed meal desolventizing process

Abstract Most oilseed crushing industries use solvent extraction with commercial hexane to produce crude oils. Desolventization with steam in a desolventizer-toaster (DT) is used to remove the residual solvent from oilseed meals. In this study, a mathematical model is developed to simulate the desolventizing process and analyze the influence of operating variables in continuous equipment. Mass transfer phenomena are outlined to take into account different retention and transport mechanisms. Solvent diffusion through pores from the solid to the vapor phase is analyzed and the contribution of axial dispersion along the bed is evaluated. The final equations describing solvent flow in meal particles and through the desolventizer are solved by numerical techniques. The influence of processing variables such as desolventizing temperature and residence time as well as the effect of some process parameters, like particle size, oil content and void fraction in the bed, on the meal residual solvent is simulated by the model.

Effect of Drying Operating Conditions on Canola Oil Tocopherol Content

The aim of this work was to evaluate two operating parameters of seed drying (temperature and initial moisture content) on the tocopherol content of canola oil. The raw material was characterized by moisture, oil, protein, crude fiber and ash content. Seeds at 13.6% and 22.7% moisture content (dry basis, db) were dried at temperatures in the range of 35–100 °C to a safe storage moisture of 7% db. Oil was extracted from each treated sample. The oil extracted from the samples dried at the extreme temperatures was analyzed by means of the acidity value, peroxide index and fatty acid composition, finding no significant differences among treatments or among untreated and treated samples. Tocopherol contents in the oils obtained for all the assayed temperatures were determined. Differences were found for the samples with 22.7% (db) initial moisture content. Except at 35 °C, temperature affected negatively the oil tocopherol content. However, when 13.6% (db) moisture seeds were processed, no significant differences were observed in the amount of this minor oil component among assays.