Abstract
To investigate the drying characteristics and mechanism during electrohydrodynamic (EHD) drying with ultrasonic pretreatment, the ultrasonic pretreatment-assisted EHD drying method at different power values was used to carry out the drying experiment of potatoes. To carry out this study, potato slices were pretreated with different ultrasonic power values (150, 180, 210, 240, and 270 W) or without ultrasound for 30 min at 30°C. The corresponding voltage was 18 kV during EHD drying. The moisture ratio, drying rate, color, shrinkage, and rehydration rate of potatoes were determined. The microstructure of potatoes was analyzed using infrared spectroscopy and scanning electron microscopy. Eight mathematical models were used to fit the drying of potatoes. Results showed that, compared with the control group, the ultrasonic pretreatment combined with the EHD drying group had improved the drying rate of potato slices, which was different at varying ultrasonic power values. Ultrasonic pretreatment had a remarkable effect on the color of the potato but had little effect on the shrinkage rate. The maximum rehydration rate is 5.7704 at 180 W. The minimum and maximum values of effective moisture diffusivity (Deff) were 3.4070 × 10−7 m2/s and 4.1160 × 10−7 m2/s, respectively. The effect of ultrasonic power pretreatment on the microstructure of potato in the EHD drying process was significant ( p > 0.05 ). According to the statistical parameter evaluation, eight mathematical models could satisfactorily describe drying curves of potato slices dried under EHD with ultrasonic pretreatment, and the logarithmic model was best suited. This work provides a theoretical basis and practical guidance to further understand the parameter characteristics and mechanism of ultrasonic pretreatment combined with the EHD drying technology.
Highlights
Potato, an annual herb of Solanaceae, is the fourth most important food crop in the world after rice, wheat, and corn
Jarahizadeh and Taghian Dinani used ultrasonic pretreatment combined with convection to dry potatoes and concluded that the rates of decrease in the moisture content of the ultrasonic pretreatment groups are significantly higher than those of the control group [24]. e results of ultrasonic pretreatment combined with infrared freeze-dried sweet potato slices show that the moisture content of sweet potato after ultrasonic pretreatment decreases faster than that of the control [25]. ese findings were consistent with our experimental results
Results are shown in Table 5. e R2 values of eight models were greater than 0.95 (Table 5), indicating that the eight thin-layer drying mathematical models could be used to simulate the drying process of potato slices with different ultrasonic power values
Summary
An annual herb of Solanaceae, is the fourth most important food crop in the world after rice, wheat, and corn. More than 150 countries and regions are planting potatoes in the world. As the largest potatoes production and export country in the world, China’s potatoes storage and transportation are important. Drying is the most important and common operation in potato processing to extend the shelf life of food products by reducing water activity, introducing new forms of consumption, and minimizing waste. Drying reduces transportation, storage, packaging, and distribution costs by the decrease of product volume and weight [1]. The main drying methods of potatoes are hot-air, vacuum freeze, microwave, and infrared radiation drying methods [2]. Hot-air drying has low cost and high speed. Microwave drying has high heating efficiency, strong processing capacity, and easy operation but results in uneven drying [4]. Microwave drying has high heating efficiency, strong processing capacity, and easy operation but results in uneven drying [4]. e infrared radiation drying has an evident thermal effect on the drying process but has no evident enhancement effect on the internal mass transfer [5]. erefore, new drying technologies should be studied
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