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Effect of the moisture adsorbents on shallot bulb drying

Muftia Chairin Nissa1, Dewi Qurrota A’yuni1, Setia Budi Sasongko1, Aji Prasetyaningrum1, Mohamad Djaeni1*, Ching Lik Hii2

1Department of Chemical Engineering, Faculty of Engineering, Diponegoro University Jl. Prof H. Soedarto, SH, Tembalang, Semarang, Indonesia

2Food and Pharmaceutical Engineering Research Group, Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, Malaysia Campus, Semenyih 43500, Selangor Darul Ehsan, Malaysia


Ingredient deterioration, extended drying times, and inefficient energy use are still issues with current shallot bulb drying. As a result, it is suggested that air dehumidification using solid adsorbents increase the driving force in shallot drying. Zeolite and silica, which were used in this study as moisture adsorbents, increased the mass transfer of water from shallot to air. Dehumidification was used to dry about 25 kg of fresh shallots for 4 hours at temperatures of 30 °C, 40 °C, and 50 °C, with an average air velocity of 7.8 m/s. Results indicated that using adsorbents throughout the drying process could speed up the reduction of moisture content. In addition, Page’s model predicted accurately the rate of shallot bulb drying for any variable. The total phenolic compounds (TPC) decreased at higher drying temperature and longer drying time. The addition of zeolite can keep the TPC high. Meanwhile, the thermal energy efficiency rose at higher temperatures. Response surface methodology (RSM) determined that air dehumidified by zeolite at a drying temperature of 50 °C produced the best of shallot drying results.

Keywords: Shallot bulbs, Adsorbent drying, Total phenolic, Mathematical modeling

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