*2.2. Materials*

Material used in the study consisted of plum (*Prunus domestica* L.) (cv. Valor) juice obtained by laboratory hydraulic press (SRSE, Warsaw, Poland) that was used for preparation of polyphenolic extract. This was done by application of amberlite XAD-16 resin previously washed with water. The absorbed compounds were removed by ethanol that was evaporated by rotary evaporator Laborota 20 (Heidolph, Schwabag, Germany) at 40 ◦C to avoid the excessive degradation of the polyphenols. The solution was divided into 100 mL portions and subjected to the drying processes without the addition of any carrier agent due to the sugars' removal [5].

## *2.3. Drying Procedure*

The plum juice extracts were submitted to drying techniques: (a) freeze-drying (FD) was performed in freeze-dryer (FreeZone, Labconco Corp., Kansas City, MO, USA) for 24 h (temperature of the chamber −60 ◦C and the heating plate +25 ◦C); (b) vacuum drying (VD) in Vacucell 111 Eco Line (MMM Medcenter Einrichtungen GmbH, Planegg, Germany) at the temperature of 40 ◦C, 60 ◦C and 80 ◦C at a pressure of 300 Pa for, respectively, 20, 16, and 10 h; (c) spray drying (SPD) done by mini spray dryer (Buchi, Flawil, Switzerland) with the inlet temperature of 180 ◦C and the outlet temperature of 70 ◦C. All drying techniques were performed at least in duplicate (*n* = 2). The obtained plum extracts powders (PEP) were milled (Bosch MKM 6003c, Gerlingen, Germany), vacuum packed (PP-5.14, Tepro SA, Koszalin, Poland), and stored at −20 ◦C until they were analyzed.
