## 1 Introduction  
Preliminary work on the application of dehumidified air (DA) for the improvement of drying process conditions was carried out in the late 1980s by [PERSON] and in the late 1990s by [PERSON] et al. [1, 2]. Reduced drying air humidity increases the driving force of the process, which lowers the drying temperature [3]. Few researchers have reported DA-assisted drying on a laboratory scale. Moreover, experiments conducted on DA application for drying process were usually performed using one level of air humidity. [PERSON] and [PERSON] (2004) who dried figs with controlled air humidity with the thin-layer method, applied only one level of humidity and the relative humidity was 10% [4]. In their work on dehumidified air spray drying (DASD) over many years, [PERSON] and [PERSON] studied tomato pulp and orange juice concentrate spray drying, also using only one level of air humidity [5; 6; 7]. The authors demonstrated that the residue accumulation in tomato pulp spray drying was reduced in comparison to conventional spray drying (SD) due to the application of DA. The researchers found as well that DA application promoted rapid particulate skin formation, which in consequence decreased the powder moisture content and increased powder bulk density and solubility. As for the orange juice concentrate SD, the authors observed that using maltodextrin (MD) as a carrier in combination with the DASD was also found to be an effective way of reducing residue formation. Therefore, this implies that solely decreasing drying air humidity, while the drying air temperature remains at the standard level for SD, demonstrates effectiveness for process performance and powder properties. However, it should be underlined that this approach fails to take into account other process parameters which can be crucial for potentially improving the course of drying. In recent years, there has been growing interest in DASD as a result of initial research involving one level of reduced drying air humidity in SD, while other parameters remained typical for SD. The researchers focused on the significant modification of drying parameters in comparison to conventional SD. [PERSON] et al. (2019) described spray drying of honey with the application of DA [8]. The authors significantly modified the process parameters in comparison to conventional SD as the inlet drying temperature was reduced to 75 \({}^{\circ}\)C and feed solid concentration was increased up to 60%. Therefore, due to lower stickiness, it was possible to reduce carrier content down to 20% solids, which can be marked as considerable progress in honey SD, because honey powder is usually produced with a minimum of 50% carrier solids. Furthermore, the process can be described as successful in recognizing very high powder recovery (93%), which has not been noted in the literature before for sugar-rich materials. Therefore, dehumidified air spray drying (DASD) has drawn attention not only as a method to increase powder recovery, but also as a method that allows to decrease or avoid stickiness during the production of powders from some sugar-rich materials, which are generally recognized as difficult to dry [9]. The principle of this spray drying approach is based on the significant reduction in air temperature (even down to 75 \({}^{\circ}\)C inlet) which helps to avoid stickiness related to low glass transition temperature (\(T_{g}\)) of a raw material. DA provides additional driving force for water evaporation, so it is possible to produce powder at a considerably low temperature for SD [10]. The reduction in stickiness reduces the carrier content, i.e., as was presented for honey down to 20% or to 10% for white mulberry molasses [8; 11]. It was also possible to eliminate carriers completely during DASD of materials such as blackcurrant juice concentrate, purple carrot juice concentrate and mango pulp [12]. Thus, DASD enables us to produce powders of a high share of raw material being potent in bioactive compounds, which is important in the formulation of functional food products.