The influence of different the drying methods on chemical composition and antioxidant activity in chokeberries

Drying has been long known and widely used method of food preservation. The aim of this study was to determine the effect of different drying methods (by freeze-drying (FD), vacuum (VD), convective drying (CD), microwave (VMD) and combined method (CVM)) on the quality factors of chokeberry fruit, including phenolic compounds, antioxidant activity, and color. All products were characterized by water activity which determines their storage stability. The highest content of bioactive compounds and antioxidant activity were determined in freeze-dried samples, compared with fresh fruits (total phenolic in gallic acid equivalents- 8008 mg/100 g dm, anthocyanins- 3917 mg/100 g dm). The increase in air temperature during CD as well as the increase in material temperature during VMD deteriorated dried product quality in terms of the content of phenolic compounds, antioxidant activity, and color, which was correlated with anthocyanin content. A new combined CVM method allowed obtaining high quality dried material compared to the CD and VMD methods applied separately. The drying process affected changes in the appearance and brightening of color, and also increased the contribution of yellow color in the fruits. The results show that the quality of dried chokeberry depends on the method and conditions of fruit drying.