Thin layer mathematical modeling of convective, vacuum and microwave drying of intact and brined onion slices

Abstract

Drying of onions by convective, vacuum and microwave methods in terms of drying kinetics were investigated at various conditions. Kinetics of intact and brined onions at 50, 60, and 70°C for convective and vacuum drying, and 80, 240, and 400 W for microwave drying were obtained. Onion slices of 3 and 7 mm thicknesses either dipped into 8% NaCl solution for 40 min or intact were dehydrated. Fitting of the experimental data to 13 thin layer drying models resulted in Sigmoid model as the most suitable model for all investigated drying techniques. Sigmoid model was followed by Cubic and Midilli models with respect to R2, RMSE, and χ2. Diffusion coefficients varied between 1.962 × 10−9 and 1.372 × 10−8 m2/s for convective, 9.757 × 10−9 and 1.723 × 10−8 m2/s for vacuum and 3.193 × 10−8 and 9.139 × 10−7 m2/s for microwave drying. Activation energy values were in the range of 3.28–34.13 kJ/mol for convective and vacuum drying and 2.25–6.08 W/kg for microwave drying. Practical applications Onion (Allium cepa L.) is famous for authentic sensorial properties and used in a lot of dishes. Fresh or dried form of this vegetable contains numerous healthful compounds such as organosulfur compounds, flavonoids, fructans, vitamins, and minerals. Convective, vacuum and microwave drying of food materials are common methods applied in dehydration of foodstuffs for preservation and new product development. The aim of this study is to reveal the effectiveness and behaviors of indicated drying techniques. The comparison and selection of most appropriate dehydration procedure for onion might be of interest in food and market suppliers.

Using PSO and GWO techniques for prediction some drying properties of tarragon (Artemisia dracunculus L.)

“…The increasing of D eff values with increasing air temperature was expected because of increasing vapor pressure inside the tarragon samples. Similar results was reported by Doymaz and Bilici ()) for peach slices, by Puente‐Diaz, Ah‐Hen, Vega‐Galvez, Lemus‐Mondaca, and Scala () for Murta berries, by Doymaz () for red kidney bean seeds, by Sufer, Sezer, and Demir () for onion slices, and by Kaveh, Abbaspour‐Gilandeh, Amiri Chayjan, Taghinezhad, and Mohammadigol () for terebinth fruit.…”

Convective and microwave drying of onion slices regarding texture attributes

“…Individual samples were placed in the center of the rotating plate. For microwave drying operations, a kitchen-type microwave oven (MD 574; Arçelik, Turkey) with 17 l capacity (496 × 294 × 397 mm), at real effective power levels of 68, 204, and 340 W, was used according to Süfer et al (2017). All drying experiments were performed in triplicate.…”

“…Onion slices were dried convectively in a laboratory type natural convection oven (JSON-250; JS Research, USA) in glass Petri dishes (120 × 17 mm) in a thin layer position detailed in Süfer et al (2017). Individual samples were placed in the center of the rotating plate.…”

Convective and Microwave Drying of Mushrooms (A.bisporus and P.ostreatus)

“…Conventional drying is the most common technique and microwaves supply rapid moisture removal. Heat and mass transfer occur at the same time in this processes, 11 thus some complexities could arise. In order to solve difficulties and understand the mechanism of dehydration, mathematical models could be helpful.…”

“…To calculate effective moisture diffusivities (D eff ), Fick's second law for cylinder geometry was accepted. 11 On the other hand, Arrhenius type equation was valid for the activation energy (E a ) of convective drying, however in microwave; this equation was modified by Dadali and Özbek, 2008. …”