Modelling of drying kinetics and comparison of two processes: forced convection drying and microwave drying of celery leaves (Apium graveolens L.)

Abstract

The purpose of this work is to compare two processes: forced convection drying and microwave drying of celery leaves (Apium graveolens L.). This comparison is based on kinetical parameters, moisture diffusivity, variation of the drying rate and energy consumption calculation of both processes. The drying experiments were carried out at different air temperatures (40-120 °C) and at different microwave powers (100-1000 W).Twenty-two empirical models were used to simulate the thinlayer drying kinetics of celery leaves and the best models were selected using three statistical criteria (R 2 , χ 2 and RMSE). Sledz's model proved to be the best for celery leaves drying kinetics description with 0.9962 ≤ R 2 ≤ 0.9992, 0.000065 ≤ χ 2 ≤ 0.000284 and 0.007979 ≤ RMSE ≤ 0.016683 for all the studied temperatures and 0.9971 ≤ R 2 ≤ 0.9989, 0.000124 ≤ χ 2 ≤ 0.000291 and 0.010910 ≤ RMSE ≤ 0.016914 for all the used powers. Moisture effective diffusivity ranges from 2.22×10-12 to 6.40×10-11 for convective drying and from 1.18×10-11 to 3.13×10-10 m 2 /s for microwave drying. While in the same order, the activation energies were 36.09 kJ/mol and 77.3 W/g. Regarding the energy consumption, the Specific Electrical Energy Consumption decreased with decreasing temperature or power levels, whereas the opposite was observed with Energy Efficiency. It is clear that many advantages are attributed to microwave drying, including reduced drying time, high drying rate and high moisture diffusivity, low energy consumption and significant drying efficiency, especially when power levels are high.

Microwave drying effect on drying characteristic and energy consumption of Ficus carica Linn leaves

“…The same trend was observed in the studies performed on the microwave drying of various leaves such as; purple basil leaves (Altay et al, 2019), peppermint leaves (Torki-Harchegani et al, 2016), and celery leaves (Demirhan & Özbek, 2011). Additionally, the effective diffusivity values calculated from the present study were within the general range of 10 À12 to 10 À8 m 2 /s for the food materials (Doymaz et al, 2015;Mouhoubi et al, 2019). The differences in D eff values of the food materials are mainly attributed to their composition and variety, structural geometry and drying conditions applied such as microwave power level, temperature, or pre-treatments applied (Jahanbakhshi, Yeganeh, & Momeny, 2020).…”

“…Recently, studies on microwave drying of the various leaves having the capability to be used on behalf of the living were carried out to extend the consumption periods of these food products. The leaves dried using the microwave drying technique are follows as collard leaves (Alibas, 2009), basil leaves (Demirhan & Özbek, 2010b), coriander leaves (Hihat, Remini, & Madani, 2017;Sarimeseli, 2011), celery leaves (Demirhan & Özbek, 2011;Mouhoubi et al, 2019), savory leaves (Arslan & Özcan, 2012), thyme leaves (Sarimeseli, Coskun, & Yuceer, 2014), Moringa oleifera Lam. leaves (Potisate & Phoungchandang, 2015), peppermint leaves (Torki-Harchegani et al, 2016), olive leaves (Elhussein & S ¸ahin, 2018), purple basil leaves (Altay, Hayaloglu, & Dirim, 2019), Laurus nobilis leaves (Khodja et al, 2020), and lemon-scented tea tree leaves (Saifullah, McCullum, McCluskey, & Vuong, 2021).…”

Convective and microwave drying kinetics and modeling of tomato slices, energy consumption, and efficiency

“…Substantial microwave heat absorption allows the product to have a high‐loss factor at higher MC . This increases the water vapor pressure inside the pores and induces their opening (Darvishi et al, 2016; Mouhoubi et al, 2019).…”

“…E a is the amount of energy required to remove moisture from a solid matrix (Aghbashlo et al, 2009), for which the Arrhenius equation has been represented to study the effect of temperature (Mouhoubi et al, 2019). In the case of hot air assisted drying, the relationship between temperature and D eff was used by calculating the E a according to Equation (9) (Darvishi et al, 2014): However, in the case of microwave‐assisted drying, the E a has been modified from the Arrhenius equation, it is assumed that this energy is related to the speed of the drying kinetics and the ratio of microwave power to sample weight ( m/P ), rather than to air temperature, so Equation (9) can be represented as follows Equation (10) (Darvishi et al, 2014).…”

Convective and microwave drying of coriander leaves: Kinetics characteristics and modeling, phenolic contents, antioxidant activity, and principal component analysis

“…Indeed, when shifting from the lowest temperatures or power levels leaves (Bensebia & Allia, 2015), celery leaves (Demirhan & Özbek, 2011;Mouhoubi et al, 2020), kaffir lime leaves (Tasirin, Puspasari, Lun, Chai, & Lee, 2014), peppermint (Arslan, Özcan, & Menges ¸, 2010), Piper umbellatum L. leaves (Dorneles et al, 2019), and Moringa olifera leaves (Tarafdar et al, 2021).…”