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Investigation of rehydration kinetics of open-sun dried okra samples

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Abstract

In this study rehydration kinetics of open-sun dried okra, which dried naturally and two pre-treatment, was investigated at 25 and 50 °C. By the obtained data, parameters with respect to rehydration kinetics and diffusion mechanism were calculated. In dehydration experiments, it was determined that blanching pre-treatment has influence on the drying time and okra samples were dried at 18 h. On the contrary in rehydration experiments maximum equilibrium rehydration values were achieved with the okras dried naturally. Experimental equilibrium rehydration (R eq ), theoretical equilibrium rehydration (R max ) and diffusion coefficient (D) of okra dried naturally at 50 °C were calculated as 5.57 (g water/g dry matter), 5.96 (g water/g dry matter) and 2.17 × 10−10 (m2/s), respectively. Rehydration exponent (n) value, which is also important to identify the diffusion type of dried okra, was determined as between 0.332 and 0.383. Because of the exponent value n < 0.50, diffusion was defined as natural Fick type.

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Abbreviations

M C :

Moisture content of dehydration (g water/g dry matter)

m w :

Water content (g)

m d :

Dry matter content (g)

R C :

Rehydration content (g water/g dry matter)

w t :

Weight of the samples at any time (g)

w dry :

Dry weight (g)

Req :

Experimental equilibrium rehydration (g water/g dry matter)

EWC :

Equilibrium water content

w e :

Rehydration values of okras at equilibrium (g water)

dR/dt :

Rehydration rate

(dR/dt)o :

Initial rehydration rate (g water/[g dry matter*min])

K :

Rehydration rate constant (g dry matter/[g water*min])

R max :

Denotes the degree of rehydration at equilibrium (g water/g dry matter)

t :

Time (min)

A :

The reciprocal of initial rehydration rater

B :

Inverse of the degree of rehydration at equilibrium

F :

Fractional uptake at time t

k :

Diffusion constant

n :

Diffusion exponent

r :

Radius (m)

D :

Diffusion coefficients (m2/s)

R 2 :

Coefficient of determination

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Authors and Affiliations

  1. Department of Chemical Engineering, Yıldız Technical University, Davutpaşa Campus, 34210, Istanbul, Turkey

    Özlem Gökçe Kocabay & Osman İsmail

  2. T.R. Ministry of Culture and Tourism, Directorate of Central and Laboratory for Restoration and Conservation, Istanbul, Turkey

    Özlem Gökçe Kocabay

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Correspondence to Özlem Gökçe Kocabay.

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Gökçe Kocabay, Ö., İsmail, O. Investigation of rehydration kinetics of open-sun dried okra samples. Heat Mass Transfer 53, 2155–2163 (2017). https://doi.org/10.1007/s00231-017-1972-0

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