Effect of low temperature plasma pretreatment on drying process of vegetables with waxy layer

Abstract

In this study, low temperature plasma technology was used as an efficient pretreatment method of vegetables with waxy layer before drying. The effects of different low plasma pretreatment power (200, 300, 400, and 500 W), low plasma pretreatment time (30, 40, and 50 s) and drying temperature on the thin layer drying process of vegetables (peppers, lentils, and peas) were investigated. Peppers after plasma pretreatment were dried at 45, 50, and 55 C. Lentils and peas after plasma pretreatment were dried at 65, 70, and 75 C. Results showed that low temperature plasma can effectively improve the drying efficiency, promote the moisture diffusion and shorten the drying time. After pretreatment power of 500 W for 30 s at 55 C, drying time of peppers was shortened by 18.75%, the maximum effective moisture diffusivity is 5.843 Â 10 À10 m 2 Ás À1 , and lower activation energy (Ea) is 69.349 kJÁmol À1 in comparison with 71.118 kJÁmol À1 for the control group.After pretreatment power of 500 W for 30 s at 75 C, drying time of lentils and peas was shortened by 33.33 and 27.27%, respectively. The maximum effective moisture diffusivity of lentils is 2.526 Â 10 À9 m 2 Ás À1 , and lower activation energy (Ea) is 27.359 kJÁmol À1 in comparison with 33.366 kJÁmol À1 for the control group. The maximum effective moisture diffusivity of peas is 1.867 Â 10 À9 m 2 Ás À1 , and lower activation energy (Ea) is 23.583 kJÁmol À1 in comparison with 29.107 kJÁmol À1 for the control group. Results indicate that the higher plasma pretreatment power led to the higher drying efficiency but higher plasma pretreatment time cannot further shorten the drying time. Practical ApplicationsVegetable is important in daily life, but easy to dehydrate in a natural state. The transportation and storage are more convenient after drying. Low temperature plasma technology does not need high pressure and low energy consumption, which can maintain the color and nutrition of vegetables to a large extent. In industry, it can be applied to pretreat fruits, vegetables, and other foods before drying. It can effectively enhance the drying efficiency, and shorten the drying time. | INTRODUCTIONThe outer epidermis of plants consists of cuticle and waxy layer (Roma Lucas & Santos Déborah, 2021). Waxy layer has the function of reducing water loss in plant tissue. In the present work, three vegetables with waxy layer (peppers, lentils, peas) have been observed.Fresh peppers are perishable, the loss will be very serious. Lentils and peas have the same problem. After drying, the moisture inside

Convective drying of Gardenia erubescens fruits: Effect of pretreatment, slice thickness and drying air temperature on drying kinetics and product quality

“…This suggested that the steam blanching and dipping in the ascorbic acid solution reduced the energy needed for the diffusion of moisture to the surface of the samples for evaporation as a result of a possible reduction in intermolecular bond strength. Similar findings with similar attributable reasons were reported elsewhere [ 7 , 12 , 47 , 48 ]. The R 2 range of 0.8317–0.9916 is a confirmation of the suitability of the Arrhenius-type equation in predicting the activation energy of the G. erubescens fruit slices under similar slice thickness, pretreatment and drying air temperature.…”