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<p>This paper presents new insights into the thermo-hygroscopic behavior and moisture transport of beetroot (Beta vulgaris L.) during convective drying through experimental characterization of heat and mass transfer phenomena. Theses proprieties were investigated over a temperature range of 30–60&#xa0;°C at an air velocity of 1.5&#xa0;m s⁻¹. The equilibrium moisture characteristics, drying kinetics, effective moisture diffusivity, shrinkage and the variation of apparent density as a function of moisture content were evaluated. Desorption isotherms were determined using a static gravimetric method at relative humidity levels ranging from 5% to 90%. The equilibrium moisture data exhibited Type II sigmoidal behavior and were adequately described by the Generalized GAB model with statistical performance comparable to that of a Langmuir-type formulation. Distinct constant-rate and falling-rate periods were observed in the shrinkage-corrected drying rate curves. The effective moisture diffusivity was determined from the falling-rate period using a shrinkage-corrected diffusion model and was found to increase significantly with drying temperature, from 2.64 × 10⁻⁹ m² s⁻¹ at 30&#xa0;°C to 9.33 × 10⁻⁹ m² s⁻¹ at 60&#xa0;°C. The temperature dependence of diffusivity was described by an Arrhenius relationship, yielding an activation energy of 34.86&#xa0;kJ mol⁻¹. Shrinkage was found to exert a pronounced effect on drying kinetics and on the estimation of effective moisture diffusivity. The apparent density exhibited a non-linear evolution during drying, initially increasing to approximately 1115&#xa0;kg m⁻³ and subsequently decreasing to about 1090&#xa0;kg m⁻³ indicating structural modification associated with moisture removal. The obtained results can be used for the modeling, design and optimization of convective drying processes of beetroot and other hygroscopic materials.</p>

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Characterization of heat and mass transfer in beetroot during convective drying: new insights into hygroscopic behavior and moisture diffusivity

  • 期刊论文

  • 发表日期：

    2026年6月1日

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  • Thouraya Ghnimi,
  • Lamine Hassini,
  • Emna Bettaieb,
  • Youssef Trabelsi

摘要

This paper presents new insights into the thermo-hygroscopic behavior and moisture transport of beetroot (Beta vulgaris L.) during convective drying through experimental characterization of heat and mass transfer phenomena. Theses proprieties were investigated over a temperature range of 30–60 °C at an air velocity of 1.5 m s⁻¹. The equilibrium moisture characteristics, drying kinetics, effective moisture diffusivity, shrinkage and the variation of apparent density as a function of moisture content were evaluated. Desorption isotherms were determined using a static gravimetric method at relative humidity levels ranging from 5% to 90%. The equilibrium moisture data exhibited Type II sigmoidal behavior and were adequately described by the Generalized GAB model with statistical performance comparable to that of a Langmuir-type formulation. Distinct constant-rate and falling-rate periods were observed in the shrinkage-corrected drying rate curves. The effective moisture diffusivity was determined from the falling-rate period using a shrinkage-corrected diffusion model and was found to increase significantly with drying temperature, from 2.64 × 10⁻⁹ m² s⁻¹ at 30 °C to 9.33 × 10⁻⁹ m² s⁻¹ at 60 °C. The temperature dependence of diffusivity was described by an Arrhenius relationship, yielding an activation energy of 34.86 kJ mol⁻¹. Shrinkage was found to exert a pronounced effect on drying kinetics and on the estimation of effective moisture diffusivity. The apparent density exhibited a non-linear evolution during drying, initially increasing to approximately 1115 kg m⁻³ and subsequently decreasing to about 1090 kg m⁻³ indicating structural modification associated with moisture removal. The obtained results can be used for the modeling, design and optimization of convective drying processes of beetroot and other hygroscopic materials.