Evaluation of thermo-physical properties and drying kinetics of carrots in a convective hot air drying system

Authors

  • Raquel P.F. Guiné 1Dep. Food Industry, Agrarian School of Viseu, Portugal 2CI&DETS, Polytechnic Institute of Viseu, Portugal 3CERNAS, Polytechnic Institute of Coimbra, Portugal
  • João Carlos Gonçalves 1Dep. Food Industry, Agrarian School of Viseu, Portugal 2CI&DETS, Polytechnic Institute of Viseu, Portugal
  • Ana Rita Calado 1Dep. Food Industry, Agrarian School of Viseu, Portugal
  • Paula Correia 1Dep. Food Industry, Agrarian School of Viseu, Portugal 2CI&DETS, Polytechnic Institute of Viseu, Portugal

Keywords:

kinetic model, mass transfer coefficient, enthalpy, thermal conductivity, diffusivity, heat transfer coefficient

Abstract

This paper presents an experimental study on the evolution of carrot properties along convective drying by hot air at different temperatures (50ºC, 60ºC and 70ºC). The thermo-physical properties calculated were: specific heat, thermal conductivity, diffusivity, enthalpy, heat and mass transfer coefficients. Furthermore, the data of drying kinetics were treated and adjusted according to the three empirical models: Page, Henderson & Pabis and Logarithmic. The sorption isotherms were also determined and fitted using the GAB model. The results showed that, generally, the thermo-physical properties presented a decline during the drying process, and the decrease was faster for the temperature of 70ºC. It was possible to verify that the Page model presented the best prediction ability for the representation of kinetics of the drying process. The GAB model used to fit the sorption isotherms showed a good prediction capacity and, at a given water activity, despite some variations, the amount of water sorbed increased with the decrease of drying temperature.

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Published

2016-09-28

Issue

Section

VI-Postharvest Technology and Process Engineering