RHEOLOGICAL CHARACTERISTICS OF PROANTHOCYANIDIN POLYMERS FROM PINUS-RADIATA .2. VISCOELASTIC PROPERTIES OF SEQUENTIAL ALKALINE EXTRACTS BASED ON PHENOLIC-ACID FRACTION

Steady and dynamic oscillatory rheometry were used to characterize two members of the plant polyphenols from Pinus radiata bark, water-solub le proanthocyanidin polymers, and phenolic acids. The viscosity-contro lling factor of the extracts could be revealed by examining the variou s extracts under different chemical and theological environments. Wate r-extracted (100 degrees C) bark was successively extracted with aqueo us NaOH solutions of increasing alkalinity at 100 degrees C and the th eological characteristics of the each fraction were examined in detail . The significant viscoelasticity of the 100 degrees C aqueous NaOH se quential extracts suggests that this fraction can have a critical impa ct on the flow characteristics of overall extracts and arises from a m ajor contribution of colloidal interactions involving the carbohydrate component. (C) 1995 John Wiley and Sons, Inc.