Enzyme activity effects in fruit juice processing present contradictory results in the literature but they constitute one of the most important problems in quality control. Research has been focused on inactivating enzymes at the highest possible pressures, while not many reports on shelf life stability of fruit juices treated by HPP are available. The aim of the present study was to optimize conditions of an HPP treatment used to inactivate enzymes in apple juice and evaluate the effect of storage temperature in nutritional and quality changes after treatment for 34 days. was linear between 0.08 and 1.25 mmol/L Trolox solution. Results were expressed as TEAC value in mmol/L. Additional dilutions were needed if the DPPH value measured was over the linear range of the standard curve.