The aim of this work was to investigate an enzymatic process to decrease the chlorogenic acid (CGA) content in a model system with pure CGA as substrate. The results obtained in the model system indicated that CGA can be decreased by 98% in a 3 h reaction time period. The effects of pH, temperature, and enzyme and substrate concentrations on the rate of the enzymatic reaction were studied. It was found that the optimum pH and temperature were 4.3 and 45 degrees C, respectively. For low enzyme concentrations, a linear relationship exists between the enzyme concentration and the initial reaction rate. However, this linearity disappears when the enzyme concentration was higher than 1 nk-at/mL. With respect to the CGA concentration, the enzyme was saturated with substrate when its concentration was 0.13 mM. The kinetics of CGA decrease in the model system was also investigated. The results from this study can help to understand better the enzymatic process in a more complex system where sunflower meal is used as a source of substrate. (c) 2006 Elsevier Ltd. All rights reserved.