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- Kinetic study on microstructural changes during convective air drying of grapesPublication . Ramos, Inês N.; Silva, Cristina L. M.; Sereno, Alberto M.; Aguilera, José M.
- Modeling drying kinetics of dominga grapesPublication . Ramos, Inês N.; Silva, Cristina L. M.
- Kinetic study on microstructural changes during convective air drying of grapesPublication . Ramos, Inês N.; Silva, Cristina L. M.; Sereno, Alberto M.; Aguilera, José M.
- Quantification of the effect of drying conditions on plum microstructurePublication . Ramos, Inês N.; Silva, Cristina L. M.; Cadoche, L.; Aguilera, José M.
- Integrated approach on solar drying, pilot convective drying and microstructural changesPublication . Ramos, Inês N.; Brandão, Teresa R. S.; Silva, Cristina L. M.Solar drying of foods is an old technique, still used nowadays. Nevertheless, the mathematical approach of the complex phenomena involved is not completely integrated. Drawbacks appear in modelling heat transport, specially related to the huge variability of meteorological factors. The great dependence of the heat and mass transfer model parameters on water content is also frequently forgotten. Macroscopic changes (e.g. shrinkage) that occur during drying processes, are usually not considered in mass transfer equations, also affecting the predictive ability of the models. The objective of this work was to develop the mathematical basis and considerations for integrating heat and mass transfer phenomena, taking into consideration macroscopic changes and their correlation to changes at microscopic level (e.g. cellular shrinkage), that might occur during solar drying of grapes.
- Air relative humidity effect on drying kinetics of lambertin apricotsPublication . Ramos, Inês N.; Silva, Cristina L. M.
- A new methodology for optimizing solar drying of fruitsPublication . Ramos, Inês N.; Silva, Cristina L. M.
- Quantification of microstructural changes during first stage air drying of grape tissuePublication . Ramos, Inês N.; Silva, Cristina L.M.; Sereno, Alberto M.; Aguilera, José M.Microstructural changes in cells of Ruby grape (Vitis vinifera) quarters were monitored during first stage of convective air drying, under a stereo-microscope. A gradual overall shrinkage of grape cells was observed during the process. The cellular parameters: area, perimeter, major and minor axis length, Feret diameter, elongation, roundness and compactness, were quantified by image analysis. It was verified that cell dimensions suffered modifications during drying, but their shape remained unchanged. These microstructural changes showed a smooth exponential decrease with time, and a first-order kinetic model was satisfactorily fitted to the data. Temperature increased the rate of cellular shrinkage and this effect followed an Arrhenius type behaviour. Increasing temperature from 20 to 60 C resulted in a 350% increase of the area change rate. For the parameters related to cellular dimensions, the magnitude of the values were 10 3 min 1 for the rate of change at 40 C and 3 kJ/mol for the activation energy
- Modeling drying kinetics of dominga grapesPublication . Ramos, Inês N.; Silva, Cristina L. M.Air drying kinetics of grapes (Dominga variety) were determined at 30, 40 and 50°C and velocities of 0.45 and 0.60 m/s, using a pilot tunnel tray drier. The air relative humidity ranged from 3 to 35%. The characteristic drying curves presented a single falling-rate behavior. Several models were attempted to fit the drying data. The effect of temperature on grape drying kinetics was also quantified. Air velocity had no significant effect on drying rates, in the tested range. The exponential model presented the best fit, and a drying rate and equilibrium moisture content were obtained for each isothermal experiment Temperature influence on drying rate followed an Arrhenius type behavior. A one-step non-linear regression to all the data allowed to obtain an activation energy of 31.8 :!:0.3 kJ/mol and a mean equilibrium moisture content of 0.338 :!:0.007 kg water/kg d.m. The developed model is crucial for simulating drying times of Dominga grapes.