Modeling kinetics of convective drying of Curcuma longa L.

Maria S Lima,Daniel E C Oliveira,Marco A P Silva,Lígia C De M Silva,Samuel V Ferreira,Paulo V T Leão

doi:10.1590/1807-1929/agriambi.v25n3p197-202

Maria S Lima, Daniel E C Oliveira + Show 4 more

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https://doi.org/10.1590/1807-1929/agriambi.v25n3p197-202

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Abstract

ABSTRACT This study aimed to determine drying curves of land saffron (Curcuma longa L.) rhizomes at different temperatures and ventilation conditions to adjust non-linear regression models, and to calculate effective diffusion coefficients and activation energies. Saffron rhizomes were randomly collected in natura with a hoe from the soil in Rio Verde, Goiás, Brazil. They were subsequently sized, sanitized, and sliced into 2.63 ± 0.1 mm thick sections. Rhizomes were dried in an oven with forced air ventilation at 45, 55, 65 and 75 °C for 18, 14, 10 and 9 hours, respectively. As the temperature increased, drying time was reduced. Consequently, moisture content also decreased, facilitating the drying process by decreasing the energy required to remove water molecules. Among the analyzed models, the Midilli model was best adjusted to the data under different drying air conditions. Effective diffusion coefficients (D) were 9.17 × 10-11, 13.33 × 10-11, 20.09 × 10-11, and 35.89 × 10-11 m2 s-1 at 45, 55, 65 and 75 °C, respectively, increasing with higher temperatures. Activation energy for liquid diffusion during drying was 21.186 kJ mol-1.

Highlights

Saffron rhizomes are often dried and ground into powder for coloring purposes because of their bright yellow color
This study aimed to determine drying curves of land saffron (Curcuma longa L.) rhizomes at different temperatures and ventilation conditions to adjust non-linear regression models, and to calculate effective diffusion coefficients and activation energies
Saffron rhizomes were randomly collected in natura with a hoe from the soil in Rio Verde, Goiás, Brazil

Summary

Introduction

Saffron rhizomes are often dried and ground into powder for coloring purposes because of their bright yellow color. Mathematical modeling of drying kinetics have been reported for many different products, such as banana slices (Leite et al, 2015), cambre seeds (Faria et al, 2012), black saffron (Lakshmi et al, 2018), strawberries (Oliveira et al, 2015), and babassu mesocarp (Rosa et al, 2017). Studies are still needed to identify the best model to define drying kinetics of saffron. The objective of this study was to characterize the kinetics of drying saffron rhizomes to obtain flour by mathematical modeling, and to determine effective diffusion coefficients (D), activation energies, and thermodynamic properties at 45, 55, 65 and 75 °C. Non-linear regression models used to represent the drying of plant products were adjusted to the experimental data on drying saffron (Table 1)

Material and Methods

Conclusions

Findings

Literature Cited