## 1 Introduction  
Drying is one of the oldest and most commonly applied operations in food processing. The aim of drying is the reduction in both the water content and water activity of the product, which results in a prolonged shelf life of food [1, 2]. There are many different methods of water removal by drying, starting with the convection (hot air) drying method as the most popular. Despite its simplicity, convection drying is associated with many drawbacks, which is why unconventional techniques were implemented such as microwave-assisted drying, microwave-vacuum drying, and infrared drying. Among all water removal methods, freeze-drying is considered as a benchmark technology since it allows high-quality dried products to be obtained. Due to the reduced amount of free water and the low temperature during the process, suppressed microbiological activity can be achieved. In addition to this, the primary shape and structure of the product can be maintained due to ice formation and its further sublimation [3, 4, 5, 6]. The dissolution of the phenolic compounds in the plant materials is affected by material processing. The relatively low drying temperature during freeze-drying allows for increased retention of phenolic compounds in the dried material and has a positive effect on their bioaccessibility. Thereare also processes that can modify the polyphenol profile. One of them is fermentation, during which, as a result of microbiological activity and enzymatic decomposition, the concentration of some metabolites may increase, while that of others may fall [7; 8]. Despite several advantages in quality, the high operating and maintenance costs make freeze-drying one of the most expensive methods of dehydration. These costs result from the long drying time under continuous vacuum and the need for freezing the material before drying [9]. Thus, freeze-drying is mainly used for high-quality products. To increase its efficiency, different emerging technologies can be used such as pulsed electric field treatment. Pulsed electric field (PEF) technology opens new horizons for existing applications in the field of unit operations, which aim towards water removal. It has been previously demonstrated that PEF treatment enhances convection drying [10; 11; 12; 13], vacuum drying [14; 15; 16], and microwave drying [17; 18]. Moreover, it has been proven that application of PEF enhances freeze-drying time and it can eliminate the need for external freezing of the raw material before freeze-drying since the product can be frozen by the vacuum method during pressure drops inside the drying chamber [19; 20]. The reason why PEF treatment intensifies dehydration is associated with its impact on cellular systems. The mechanism of PEF can be explained by the electroporation phenomenon [21]. Electroporation depends on the formation of pores across the cell membrane owing to the application of very short pulses characterized by very high electric field intensity. The pores are formed when the transmembrane potential of the cell exceeds a critical value. The process of pore formation can be irreversible and generally lead to permanent damage to or the death of the cell, or reversible when the cell can restore its normal functionality. The nature of the process depends on the processing parameters and properties of the treated material [11; 22; 23]. The beneficial effect of PEF pretreatment on the mechanical, thermal, optical, and microstructural properties of freeze-dried plant material was demonstrated, using mainly apples and strawberries as matrices. The obtained results showed that due to the electroporation phenomenon of PEF, a more homogenous distribution of sugar and water inside tissue leads to more uniform drying. Moreover, texture and acoustic analyses stated that the PEF-treated material has a greater porosity and crispness compared to the untreated one [24]. However, the literature about the quality of freeze-dried products produced with the assistance of PEF is limited.