Thermal and high pressure stability of tomato lipoxygenase and hydroperoxide lyase

Thermal and high pressure stability of tomato lipoxygenase (LOX) and hydroperoxide lyase (HPL) in a tomato juice were studied in the temperature and pressure range of 25-90 degrees C and 100-650 MPa. As for thermal stability of LOX, no inactivation is observed for temperatures below 40 degrees C whereas it is completely inactivated by a treatment of 60 degrees C for 12 min. On the other hand, HPL is a relatively heat labile enzyme; its activity is reduced to 50% after 12 min at 40 degrees C. With regard to high pressure treatments, a pressure treatment of 300 MPa allows to inactivate 20% of the HPL activity; at this pressure level HPL is more pressure sensitive than LOX. On the other hand, a residual fraction of 20% remains active even after a treatment of 12 min at 650 MPa. (c) 2006 Elsevier Ltd. All rights reserved.