The effect of reactor design and water extraction parameters under subcritical conditions on the quality of extracts from oak bark (Quercus robur L.)

An extn. cell (40 L) was designed for obtaining polyphenols and flavo- noids from bark of oak (Quercus robur L.) with water under subcrit. conditions. The antioxidant activity was assessed by using a 2,2-diphe- nyl-1-picrylhydrazyl radical scavenging method. The UV-Vis spectro- photometry was used for anal. of the exts. A high correlation between process temp. and ext. quality was found. Both total contents of poly- phenols and flavonoids as well as the antioxidant activity increased with increasing temp. up to 117.2 degrees C, 116.5 degrees C, and 123.2 degrees C, resp. Further increase in temp. resulted in deterioration of the ext. quality. The expts. were carried out according to the Box-Behnken method.