Far Infrared Drying Characteristics of the Microwave-Steamed Sweet Potato

  • Dong Il Lee
  • Jung Hyun Lee
  • Yun Sik Shin
  • Byeong Hyo Cho
  • Chung Su HanEmail author
Original Article



In this study, we aimed to investigate far infrared drying characteristics of microwave-steamed sweet potatoes and to establish optimum far infrared drying conditions.


The sweet potatoes steamed by microwave for 15 min were far-infrared-dried to a final moisture content of 25 ± 0.5% (w.b.) base on the dried sweet potato sold on the market. The thickness conditions were 2 conditions of 8 mm and 10 mm. The far infrared drying conditions were drying temperature of 60, 70, and 80 °C and air velocity of 0.6 and 0.8 m/s.


Optimum microwave steam time for sweet potatoes was 15 min. The far infrared drying time of microwave-steamed sweet potatoes showed a tendency to shorten as the drying temperature was high, the air velocity was fast, and the thickness was thinner. The color difference was lower in the condition of low drying temperature, the slow air velocity, and the thin thickness. Soluble solids contents after far infrared drying increased by 3.09~6.49 Brix compared with that of before drying. Moreover, the soluble solids contents were increased with thinner thickness, higher drying temperature, and slower air velocity. The energy consumption to remove 1 kg of moisture was decreased in the condition of high drying temperature, slow air velocity, and thin thickness.


The using of microwave steam process instead of conventional water steam process as pre-treatment before the drying of sweet potato was considered to have the advantage such as decreased drying time, lower color difference, and lower energy consumption.


Far infrared drying Microwave steam Optimum drying condition Soluble solids contents Sweet potato 


Compliance with Ethical Standards

Conflict of Interest

The authors declare that they have no conflict of interest.


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Copyright information

© The Korean Society for Agricultural Machinery 2019

Authors and Affiliations

  • Dong Il Lee
    • 1
  • Jung Hyun Lee
    • 2
  • Yun Sik Shin
    • 1
  • Byeong Hyo Cho
    • 3
  • Chung Su Han
    • 1
    Email author
  1. 1.Department of Biosystems EngineeringChungbuk National UniversityCheongjuSouth Korea
  2. 2.Department of Agricultural Engineering, RDANational Institute of Agricultural ScienceJeonjuSouth Korea
  3. 3.Laboratory of Agricultural and Food Process EngineeringHokkaido UniversitySapporoJapan

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