## 1 Introduction  
Drying is a commonly used process in the food industry, the main goal of which is to extend the shelf-life of food by removing some of the water from it [1, 2, 3]. In practice, the course of this process as well as the quality of the obtained dried material are strictly dependent on the method used [4, 5]. Hybrid drying is increasingly used to improve energy and drying efficiency. It involves combination of at least two methods of drying during a single operation or applying them sequentially--directly one method after another. The synergistic effect of several drying mechanisms, with appropriately selected process parameters, allows to reduce drying time, and thus improve the quality of the dried material by limiting colour changes, preserving smell or flavour, minimizing microstructural changes, as well as increasing the retention of bioactive ingredients [6]. Microwave-convective drying (MW-CD) is an example of hybrid drying. It combines the advantages of convective and microwave drying while minimizing the disadvantages characteristic for these drying methods [5]. Convective drying is based on the removal of water from the material, most often with hot air. The uncomplicated mechanism and relatively low costs make it one of the most frequently used drying methods in the food industry. Significant energy consumption of this method results from the low drying rate. Additionally, due to the use of hot air as a drying agent and relatively long process duration, the quality of the obtained materials is unsatisfactory [7; 8]. The use of microwave (electromagnetic waves of specific wavelength) enables quick, volumetric generation of heat (in the entire volume of the material), which causes an increase of internal pressure and pushes the water towards the surface, from where it evaporates intensively. This ensures fast drying of food at low energy consumption. One of the disadvantages of microwave drying is the risk of uneven heating. Difficulties related to controlling the temperature and the rate of drying cause this method to be most often combined with other drying methods, to prevent the risk of damaging the material [5; 6; 9; 10; 11]. In the case of MW-CD, two parameters are considered the most important--microwave power and drying air temperature. Research carried out on onions [12] showed that the assistance of hot air tunnel drying by microwaves (MW-HA) led to a reduction of the drying time by more than 90% (depending on the parameters used), and thus, a decrease of energy consumption by 3-16 times (in comparison to only hot air tunnel drying--HA). In addition, the higher the microwave power and air temperature were used, the higher the drying rate and the shorter the drying time were achieved. This tendency was also observed in the studies carried out on apples [13] and nectarines [14]. Reduced time of convective drying, caused by assisting the process with microwaves, has also been noticed in the studies conducted on durian chips [15], cherry tomatoes [16], pumpkins [17], and shiitake mushrooms [18]. Onions dried by MW-HA exhibited better rehydration properties, flavour, and colour, and also higher retention of total phenolic content and antioxidants than the ones dried with hot-air (HA) [12]. In the case of durian chips, the materials obtained by MW-HA had higher crispness and lightness, but lower hardness and shrinkage compared to HA dried samples. Additionally, a reduced energy consumption of the MW-HA method was observed, in comparison with HA method [15]. Higher retention of total phenolic compounds (including flavonoids), ascorbic acid, and lycopene, as well as better colour and texture preservation, were observed in cherry tomatoes dried by microwave-assisted hot air drying in comparison with hot air drying [16]. Pulsed electric field (PEF) is one of the nonthermal food processing techniques. The essence of its performance lies in the phenomenon of electroporation, i.e., perforation of the material's cell membrane.