Colour, moisture adsorption, and antioxidant properties of oven-dried chokeberry powder obtained after ultrasound-assisted osmotic dehydration

Osmotic dehydration (OD) of chokeberry samples in erythritol (ERT) and xylitol (XYL) solutions enhanced by ultrasonication (US) has been examined in terms of moisture adsorption, colour and antioxidant properties. After air-forced drying, the powder subjected to OD in ERT solution exhibited higher equilibrium moisture contents (EMC) in 0.20–0.45 aw than those in XYL solution. On the other hand, EMC values increased with the prolongation of US time from 5 to 30 min in the case of XYL solution. CIEL*a*b colour system was used for the determination of colour changes. While L* (the colour coordinate represents lightness (L* ~ 100) or darkness (L* ~ 0) of the sample) values decreased with the prolongation of US time from 5 to 30 min for both osmotic agents, only XYL solution caused the increase of a* (the colour coordinate represents green (−a*) or red (+a*) colour of the sample) and b* (the colour coordinate represents blue (−b*) or yellow (+b*) colour of the sample) to their maximum values at 30 min of sonication. A sample of powder subjected to OD in ERT solution has shown a higher total phenolic, total anthocyanin and antioxidant capacity. We may conclude that OD of chokeberries coupled with 30 min of sonication has resulted in chokeberry powder with the highest content of bioactive substances