Inactivation of papain by pulsed electric fields in a continuous system

Papain (E.C. 3.4.22.2), a cysteine protease in papaya, was activated with r educing agents and treated with pulsed electric fields (PEF) in a continuou s system at 10 degrees C. Irreversible reduction of activity was observed i n PEF-treated papain after 24 h storage at 4 degrees C. Oxidation of papain active site, a cyteine residue, was not the major cause of papain inactiva tion by PEF. Temperature did not increase over 35 degrees C during PEF trea tment. The pH of papain solution was not changed after PEF treatment. Struc tural change was observed in PEF-treated papain by CD analysis. Inactivatio n of PEF-treated papain was related to the loss of alpha-helix structure. H eating at 60-80 degrees C for 2 min did not significantly reduce the activi ty of papain. (C) 1999 Elsevier Science Ltd. All rights reserved.