Journal of Food, Agriculture and Environment

Microwave-assisted forced hot air circulation drying of thin-layer teff (Eragrostis tef)

Author(s):

 Tilahun Seyoum Workneh*,  Francis Collins Muga

Recieved Date: 2018-01-12, Accepted Date: 2018-03-26

Abstract:

The thin layer drying kinetics of teff kernels was investigated at a microwave power density of 2.08 W/g combined with hot air drying at 50, 60 and 70°C and an air velocity of 1.0 m/s. The drying rate at 60 and 50°C was higher than at 70°C for the first twenty minutes after which 70°C showed the highest drying rate followed by 60°C and 50°C in that order. The moisture content was reduced to below 5% after 60 min. The drying data was fitted into 12 thin layer drying models. Logarithmic model gave the best fit for the drying data with R² values of 0.9983, 0.9978, and 0.9973 at 50°C, 60°C, and 70°C, respectively. Page model, Henderson and Pabis, two-term, diffusion, and modified Midilli 1 all had R² values greater than 0.99 at all temperature levels. The effective moisture diffusivity for teff was 3.364 × 10^-10 m²/s, 3.05 × 10^-10 m²/s, and 3.51 × 10^-10 m²/s at 50°C, 60°C and 70°C, respectively, whereas the activation energy was 13.3049 kJ/mol. The drying of teff took place predominantly during the falling rate period hence could be reliably modelled by diffusion based models. The low activation energy shows that microwave assisted forced hot air circulation drying is an energy and cost effective way of drying teff.

Keywords:

Activation energy, effective moisture diffusivity, microwave, teff, thin-layer drying

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Journal: Journal of Food, Agriculture and Environment
Year: 2018
Volume: 16
Issue: 2
Category: Food and Health
Pages: 34-42

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