Enzyme sensitivity towards high pressure at low temperature

The sensitivity of several selected enzymes, e.g. Bacillus subtilis cc-amylase (BSA), peroxidase (POD), pectinmethylesterase (PME), polyphenoloxidase (PPO) and lipoxygenase (LOX) towards the combined action of high pressure (1 up to 4000 bar) and low temperature(-22 degrees C up to 0 degrees C) was investigated. The effect of a high pressure/low temperature (HP/LT) treatment on the selected enzymes was compared to the effect of a freezing process at atmospheric pressure. It was found that (i) no irreversible inactivation of POD, PPO and BSA occurred after the HP/LT treatments tested, (ii) PME was only slightly irreversibly inactivated in the selected pressure and temperature domain (92% up to 80% of activity retention) and (iii) LOX was irreversibly inactivated to a large extent (3 up to 55% of activity retention) after the selected HP/LT treatments whereas a classical freezing at -18 degrees C and atmospheric pressure caused only a 10% decrease in LOX activity. It could be observed that the enzymic activity after the treatment of both PME and LOX slightly decreased during storage in an ice bath.