Microwave and steam blanching as pre-treatments before air drying of Moringa oleifera leaves

  • Ernest Ekow Abano | ekowabano@yahoo.com Department of Agricultural Engineering, University Cape Coast, Cape Coast, China. https://orcid.org/0000-0001-8466-7811
  • Robert Sarpong Amoah Department of Agricultural Engineering, University Cape Coast, Cape Coast, Ghana. http://orcid.org/0000-0003-2168-5873
  • Catherine Mbabazi Department of Environment and Livelihood Support Systems, Faculty of Interdisciplinary Studies (FIS), Mbarara University of Science and Technology, Mbarara, Uganda.

Abstract

The objective of this work was to identify the optimal drying conditions to produce better quality dried Moringa oleifera leaves with the best drying kinetics using microwave and steam blanching pre-treatments prior to hot air drying. For this purpose, the effect of microwave power, microwave time, steaming time, and air temperature on drying kinetics and quality of Moringa leaves was evaluated using the response surface methodology. In order to achieve a moisture content of 8.0% kg H2O/kg dry matter, the optimal conditions identified were a steaming time of 2.58 min (2 min 35 sec) prior to air drying at 70°C and a microwave power of 270 W for 3 min, followed by air drying at 70°C. At this optimal condition, a confirmation test for steam-assisted air drying gave a drying time (DT) of 53 min, ascorbic acid (AA) of 2.49 mg/g, and the antioxidant activity (AOA) of 67.244% inhibition. For microwave-assisted air drying, the confirmation experiment gave a DT of 43 min, AA of 2.699 mg/g, and AOA of 74.46% inhibition. Both pre-treatments before air drying followed a falling rate drying period at the initial stages and later a constant rate drying period. Our results showed that microwave blanching should be considered as a pre-treatment in industrial production of Moringa leaves to produce better quality dried products in a relatively short time.

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Published
2020-12-21
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Original Articles
Keywords:
Antioxidant, ascorbic acid, blanching, drying, microwave, Moringa.
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How to Cite
Abano, E. E., Amoah, R. S., & Mbabazi, C. (2020). Microwave and steam blanching as pre-treatments before air drying of Moringa oleifera leaves. Journal of Agricultural Engineering, 51(4), 200-208. https://doi.org/10.4081/jae.2020.1044