Energy consumption is a great challenge during fruit drying. New techniques such as cold plasma are used as pretreatment or the main treatment for food drying. In this work, apple drying with cold plasma was investigated with COMSOL simulation. Two treatments were designed: (a) traditional air drying at 60 C and 0.5 m/s airflow, and (b) cold plasma treatment at 100 W, and 60 Hz with laminar airflow at 60 C and 0.5 m/s. The samples were two apple slices with a 6 cm diameter and 0.3 cm thickness. Results show that plasma technology without airflow does not have an effective role in drying. But the combination of plasma and airflow drying reduced the drying time from the 9,600 s to 3,600 s. The plasma-treated samples reached a constant moisture content faster than the air-dried samples. The energy consumption of drying with plasma was 85-fold lower than a traditional air-drying method. The shrinkage of plasma-treated samples was low and the total shrinkage was near the undried sample (0.008). Cold plasma probably can reduce the energy consumption, drying time, and final drying costs of fresh food drying. Practical applicationDrying with a combination of methods can reduce the processing time. In this work, the plasma technology was combined with air drying and the results show lower process time, lower shrinkage, and lower energy consumption. Plasma technology in combination with traditional air drying can reduce the drying time of food material from 9,600 s to 3,600s. The energy consumption of plasma drying was significantly lower than air drying. It can be concluded from these results that this drying method can be applied to study the drying of different types of food material.

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This study aims to simulate the effect of the drier humidity distribution on the temperature distribution and dried product shrinkage. The Lebanese yellow apple (Golden Delicious) was prepared in the form of slices with 3 and 5 mm thicknesses and dried at 60 °C in a hot air oven. Shrinkage models were determined by fitting the experimental data with Sigmaplot software. The simulation was done using these equations in COMSOL software. The simulation results showed that due to the accumulation of air humidity in one part of the oven, the temperature distribution inside the product was not distributed evenly in that part. This phenomenon caused the imbalance of moisture transfer from the product and this can increase the drying time as well as unbalanced shrinkage of the product. Finally, it was found that the air humidity distribution inside the oven had a significant effect on the drying process and shrinkage rate of samples.

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