The aim of the present work was to understand and develop a model to d
escribe the changes resin acids undergo during pine oleoresin processi
ng. Experimental data for the thermal isomerization of levopimaric aci
d, in the temperature range 155-200 degrees C, were used to develop a
kinetic model. Model validation was based on the experimental results
from the batch distillation of pine oleoresins. Both the experimental
activation energy and pre-exponential factors seem to change during th
e course of distillation, due presumably to solvent (turpentine) remov
al.