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Developing radio frequency-vacuum drying for kiwifruits

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2018 ASABE Annual International Meeting  1800599.(doi:10.13031/aim.201800599)
Authors:   Xu Zhou, Rui Li, Lihui Zhang, Shaojin Wang
Keywords:   Hot air drying; Moisture content distribution; Moisture effective diffusivity; Quality; Radio frequency-vacuum drying


To overcome main disadvantages of conventional drying methods, such as long drying time, low energy efficiency and poor product quality, developing an effective drying method is a major postharvest processing concern in the fruit and vegetable industry. The purpose of this research was to explore possible application of radio frequency (RF) vacuum technology for drying kiwifruit slices. A 27.12 MHz, 3 kW RF-vacuum drying system was used to study drying characteristics and quality attributes of the kiwifruits. The results showed that the electrode gap, vacuum pressure and sample thickness had great effects on the RF-vacuum drying. The optimal RF-vacuum drying protocol of kiwifruits was obtained with the electrode gap of 60 mm, vacuum pressure of 0.02 MPa and sample thickness of 8 mm based on acceptable drying rate, stable temperature and avoiding arcing. The RF-vacuum drying was associated with internal heating and rapid drying, resulting in 65% reduction of hot air drying (60ºC) time. Moreover, kiwifruits dehydrated by RF-vacuum drying were characterized by significantly smaller color change, higher vitamin C content and higher rehydration capacity compared with hot air dried samples (P<0.05). Although a non-uniform drying existed in the single kiwifruit slice, RF-vacuum drying achieved a relatively uniform moisture distribution among samples. Therefore, RF-vacuum drying process may provide an effective, practical and high-quality dehydration method for kiwifruits with acceptable drying uniformity.

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