Influence of temperature and drying time on extraction yield of phenolic compounds from grape pomace variety "portogizac"

The influence of drying temperature (60 °C, 70 °C, 80 °C) and fluid-bed drying time (90 min, 135 min, 180 min) on the extraction yield of phenolic compounds and antioxidant activity of extracts were investigated. The content of phenolic compounds and antioxidant activity of extracts obtained from wet grape pomace (WGP) were 73.83 mgGAE gdb-1, 42.24 mgCE gdb-1, 30.53 mg gdb-1, and 0.35 ginhDPPH gdb-1 for total phenolic compounds (TPC), total flavonoids (TF), total extractible proanthocyanidins (TPA), and antioxidant activity (AA), respectively. The applied drying conditions caused the reduction of content of all phenolic compounds down to 13.2 %, 43.1 %, 15.3 % and 21.0 % for TPC, TPA, TF and AA, respectively. The most abundant individual phenolic compound in grape pomace extracts was catechin (5.14 - 8.52 mg gdb-1). The highest content of observed compounds was retained when applying drying temperature below 70 °C for 90 minutes.