F. Chenlo
University of Santiago de Compostela
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Featured researches published by F. Chenlo.
Journal of Food Engineering | 2002
F. Chenlo; R. Moreira; Gerardo Pereira; A Ampudia
Abstract Osmotic dehydration of food involves the utilization of solutions with one or several solutes that increase considerably the viscosity of the liquid phase. As commercial sugar and sodium chloride are the common solutes employed in this type of processes, kinematic viscosities of binary and ternary aqueous solutions of these solutes were measured at various concentrations (from 0 up to 4.5 mol kg −1 at 0.5 mol kg −1 intervals) and temperatures (from 20 up to 50 °C). Additionally, densities of each solution at 25 °C are reported. Experimental data were simultaneously correlated with concentration and temperature for binary and ternary solutions with a satisfactory accuracy.
Drying Technology | 1997
G. Vázquez; F. Chenlo; R. Moreira; E. Cruz
ABSTRACT We describe a pilot-scale drying plant comprising a closed-circuit, hot-air convection chamber with a heat pump. In this plant, food and forest products can be drled with lower energy consumption and over a wider range of air, speeds, temperatures and relative humidities than in conventional driers. Also the dryinq conditions can be controlled independently of external conditions. Under several different sets of drying conditions, we determined the kinetics of dryinq of grapes that had been variously pretreated. The effects of drying conditions and the pretreatment on the drying time and the appearance of the dried product were evaluated. The drying kinetics can be described by a diffusion model.
Carbohydrate Polymers | 2012
M.D. Torres; R. Moreira; F. Chenlo; María J. Vázquez
Water adsorption isotherms of carboxymethyl cellulose (CMC), guar gum (GG), locust bean gum (LBG), tragacanth gum (TG) and xanthan gum (XG) were determined at different temperatures (20, 35, 50, and 65°C) using a gravimetric method. Several saturated salt solutions were selected to obtain different water activities in the range from 0.09 to 0.91. Water adsorption isotherms of tested hydrocolloids were classified like type II isotherms. In all cases, equilibrium moisture content decreased with increasing temperature at each water activity value. Three-parameter Guggenheim-Anderson-de Boer (GAB) model was employed to fit the experimental data in the water activity range and statistical analysis indicated that this model gave satisfactory results. CMC and GG were the most and the least hygroscopic gums, respectively. Sorption heats decreased with increasing moisture content. Monolayer moisture content evaluated with GAB model was consistent with equilibrium conditions of maximum stability calculated from thermodynamic analysis of net integral entropy. Values of equilibrium relative humidity at 20°C are proposed to storage adequately the tested gums.
Drying Technology | 2001
G. Vázquez; F. Chenlo; R. Moreira
The desorption isotherms of chestnuts (Castanea sativa Mill) were determined at 278, 293, 303, 313, and 323K by a gravimetric technique. The range of water activity was from 0.08 at 0.91. The sorption isotherms were of the type II according to Brunauers classification. The effect of the temperature shows a cross over of the desorption isotherms at water activity 0.6. The experimental data are fitted with several models (Oswin, Smith, Henderson, Halsey, and G.A.B.). Oswin and G.A.B. models gave the best fittings. Particularly, with G.A.B. model parameters some interesting information as monolayer moisture content, heat of sorption of the first and nth layer adsorbed and net isosteric heat were obtained.
Journal of Food Engineering | 1999
G. Vázquez; F. Chenlo; R. Moreira; L. Carballo
Abstract Desorption isotherms were determined at 25°C for Aledo grapes and at between 25°C and 50°C for Muscatel grapes. The efficacy of two physico–chemical pretreatments designed to accelerate grape-drying kinetics was also studied for Muscatel grapes. The isotherms obtained were fitted with various models, among which the GAB equation gave the best fits, and was subsequently used to calculate the monolayer moisture content for each grape variety. Pretreating Muscatel grapes did not greatly alter the optimal conditions for their storage and handling, suggesting that treated and untreated grapes can safely be stored under the same conditions.
Drying Technology | 1999
G. Vázquez; F. Chenlo; R. Moreira; A. Costoyas
Abstract Desorption isotherms for 1 mm thick garlic slices were determined at between 25 and 50°C and satisfactorily fitted with the G.A.B. equation. The kinetics of drying of slices of thickness 1.5 - 5.0 mm were determined at between 40 and 60°C using an air flow rate of 2.5 m-s−, and the conditions affording a high-quality product m the shortest time were identified. After establishing how the effective diffusion coefficient of the garlic slices varied with their moisture content during drying, a diffusional model accounting for these variations was developed and satisfactorily fitted to the experimental kinetic data.
Drying Technology | 2007
Luis Mayor; R. Moreira; F. Chenlo; Alberto M. Sereno
The objective of this work was to obtain experimental data and modeling of osmotic dehydration kinetics of pumpkin fruits (Cucurbita pepo L.) with aqueous NaCl/sucrose solutions. For this purpose, effective diffusion coefficients for water, sucrose, and NaCl were calculated by means of a simple model based on Ficks second law. Water loss achieved 80%, sucrose 13%, and NaCl 6% of the initial sample weight. Effective diffusion coefficients ranged from 0.58–1.40 × 10−9 m2/s, 0.75–1.23 × 10−9 m2/s, and 2.60–4.11 × 10−9 m2/s for water, sucrose, and NaCl, respectively. The proposed model gave a good correlation of the experimental data. The quality of the operation was evaluated by analysis of the values of WL/SG ratio.
Journal of Food Engineering | 2003
G. Vázquez; F. Chenlo; R. Moreira
Abstract Sorption isotherms of lupine at 25, 35, 45 °C were determined. Adsorption and desorption data were obtained at each temperature and no hysteresis was observed. The experimental method was a gravimetric static method. The results were fitted by the Guggenheim–Anderson–deBoer model. The monolayer moisture content (parameter of the model) was constant in the range of temperatures employed with a value of 0.0497 dry basis (d.b.). The isosteric heat of lupine was evaluated at several moisture content using the Clausius–Clapeyron equation and below a moisture content of 0.15 (d.b.) increases appreciably up to around 20 kJ/mol at very low moisture content.
Drying Technology | 2000
G. Vázquez; F. Chenlo; R. Moreira; A. Costoyas
ABSTRACT The drying kinetics of Muscatel grapes at 60°C and a relative air humidity of 22% were determined after various pretreatments had been applied to the grapes. The pretreatment parameters varied were the chemical agent (potassium carbonate solution with or without olive oil, or sodium hydroxide solution); the duration of pretreatment; and the temperature and concentration of the solution. A 3 minute pretreatment with an aqueous solution of K2CO3 and olive oil at 60°C reduced drying time from about 80 h to 20 h. Optimal drying load corresponded to a single layer of almost close-packed grapes on each tray. The experimental drying kinetics were satisfactorily reproduced by a model in which both grape size and the effective coefficient of diffusion are functions of moisture content.
Drying Technology | 2011
R. Moreira; F. Chenlo; M.D. Torres; C. Silva; D. M. Prieto; A. M. M. Sousa; L. Hilliou; M. P. Gonçalves
Drying kinetics of biofilms from chestnut starch and hybrid carrageenan were experimentally determined and modelled. The biofilms were obtained by mixing the respective solutions (4.0% w/w) of both substances in the proportion 80/20 of chestnut starch/hybrid carrageenan. Glycerol (at 5.0% w/w) was added to some biofilms. Biofilms were prepared using a casting method. Drying kinetics were performed at 30, 40, and 50°C for forced air convection (1.8 ± 0.1 m/s) and 30 and 50°C for natural convection. Constant drying rate period, above critical moisture content (5.4 and 4.2 kg water/kg d.b. without and with glycerol, respectively) allowed the evaluation of the heat transfer coefficients. The water diffusion coefficients were determined in the falling rate period assuming a semi-infinite slab with variable thickness. Water sorption isotherms of biofilms at 25°C were determined and fitted with the GAB model. Mechanical properties of different biofilms showed no significant differences for Youngs modulus values (44.0 ± 4.6 MPa). Nevertheless, films prepared at 30°C under natural drying showed the lowest values of tensile strength and elongation (32.2 ± 4.9 MPa and 0.85 ± 0.11%).