The influence of drying method to the changes of bioactive compounds in lingonberry by-products
The aim of this research was to evaluate the effect of different drying methods on industrially obtained lingonberry pulp juice by - products. For investigations, by - product was dried using hot air dryer (at temperatures 80 °C , 60 °C and 40 °C ), microwave - vacuum dryer and freeze - dryer. The freshly defrosted by - product was used as control. All samples were analysed on the basis of their moisture content, colourimetric attributes (CIE L*a*b* colour system), content of vitamin C (iodometric method), content of total carotenes (TC), total phenol content (TPC), total anthocyanin content (TA) and antiradical activity (DPPH, ABTS + ). The obtained data on content of vitamin C showed a 10% decrease between control and sample dried in hot air at 80 °C . Similar changes were noticed with total anthocyanin content, the lowest amount was also foun in this sample ( 306.72 ± 18.32 mg 100 g - 1 DW). Total carotenes content was higher in freeze - dried sample (5.61 ± 0.16 mg 100 g - 1 DW) which was very close to control sample. A significant loss of total phenol content was noticed after drying, up to 80%, similar ten dencies were noticed with changes of antiradical activity. After evaluating the obtained data, the use of hot air dryer at 80 °C temperature resulted in the lowest amount of vitamin C and anthocyanins in lingonberry by - products, which makes this method unsuitable for drying by - products of these berries. However, vacuum assisted microwave drying and freeze drying showed less damaging impact on dried material.