Condensed tannins extracted from eucalyptus bark waste

Abstract

This study aimed to evaluate the quantity of condensed tannins in the waste of eucalyptus bark extracted according to two salt concentrations and two analysis methods (Stiasny number and ultraviolet method). Tannins were extracted using water and sodium sulfate (Na 2 SO 4 ) and sodium carbonate (Na 2 CO 3 ) solutions in different concentrations (0, 4, 6, 8 and 10%). The influence of the different concentrations of chemical compounds (Na 2 SO 4 and Na 2 CO 3 ) on yield and extract characteristics was evaluated: content of total solids, tannins yield, non-tannins yield, pH, polyphenols yield by Stiasny reaction, and content of reactive polyphenol by ultraviolet method. The results showed that the extraction with sodium carbonate (8%) provided higher amounts of tannins extraction, and sodium sulfate (4%) provided lower amounts. The influence of 8% of sodium carbonate on the eucalyptus bark characteristics in extraction provided the highest Stiasny number and content of tannins. This method also enabled a high extraction yield, indicating the importance of using this concentration of salt in the extraction process. The highest gravimetric tannins yield was 4% for sodium sulfate. Thus, eucalyptus bark may be used in tannins extraction since it is easily available and enables a good yield and quality of tannins.