**1. Introduction**

Diets rich in fruits are beneficial to human health because of their polyphenolic compound content. In this regard, plums (*Prunus domestica* L.) represent an excellent source of such components, which can contribute significantly to the prevention of several diseases [1]. This fruit is cultivated all over the world and its production in the last 10 years has exceeded 11 million tons [2]. Plum is a seasonal fruit, and the harvest period and the period of supply of fresh fruit are relatively short. Therefore, plums cannot be consumed fresh throughout the year, thus, the development of new dried powder products, obtained by drying industrial techniques, offers an alternative for the consumption at any season of the year. Plum powders can be obtained from whole fruit [3], plum by-products [4], or juices/concentrates [5]. Commonly used drying industrial processes include, apart from conventional

air-drying, freeze-drying (FD), vacuum drying (VD), and spray drying (SPD) [6]. However, the drying techniques, used to obtain powders from whole fruit, modify some of their physical and chemical properties [3,7]. In general, FD is considered one of the best method of obtaining high-quality products because the absence of liquid water and the low temperatures required for the process allows relatively high retention of bioactive compounds [8]. VD partially prevents thermal degradation of bioactive compounds in raw material because the temperature of the product is usually low and can be easily controlled [9]. And SPD is an effective technique in drying liquid products directly into powders, and is used broadly in processing dairy and fruit products, i.e., juices, extracts, or concentrates [10], and the resulting powders present a better preservation and retention of polyphenolic compounds [11,12]. Numerous studies confirmed that the above-mentioned processes had a strong influence on the physical properties of the dried whole fruits and pomace [3,5,13], as well as of the fruit juice powders [12].

Plums are phenolic-rich fruits that contain a mixture of polyphenolic compounds that can exert several biological effects, including antibacterial [14,15], antioxidant [5,16], and anti-inflammatory properties [17,18]. In commercially available plums, the most predominant and bioactive relevant compounds are phenolic acids, such as chlorogenic and neochlorogenic acids; flavonol glycosides, quercetin-3-glucoside and quercetin-3-galactoside; and anthocyanins, such as cyanidin and peonidin [19]. However, the profile and level of bioactive polyphenolic compounds in dried plum products is affected by the drying industrial processes. Until now, there is a lack of information in the literature on how the drying processes can modify the biological properties of fruit powders, regardless of the type of the fruit used for drying. Therefore, the objective of the present study was to evaluate the influence of different drying techniques applied for preparation of plum juice extract powders on the physical properties and the alterations in polyphenolic compounds contents and bioactive properties, i.e., antibacterial, antioxidant, and anti-inflammatory.
