Inactivation of plant pectin methylesterase by thermal or high intensity pulsed electric field treatments

A comparative study between new and traditional food preservation technologies was performed on pectin methylesterase (PME) inactivation from different plant sources. PME was extracted from carrots, tomatoes, bananas and oranges and was purified by affinity chromatography. Its inactivation was investigated during high intensity pulsed electric fields (HIPEF) and thermal treatments. Thermal treatment was performed at temperatures from 54 degrees C to 81 degrees C and up to 120 min treatment time. PME inactivation was adequately described by a first-order kinetic model for PME from bananas, carrots and tomatoes, whereas a biphasic model described adequately thermal inactivation of orange PME. The thermal stable fraction of orange PME was the least sensible to heat and carrot PME was the most thermally sensitive. HIPEF treatment consisted of 40-mu s-square-wave pulses applied up to a total treatment time of 1.6 ms at 0.5 or 5 Hz and an electric field between 13.2 and 19.1 W/cm. The higher the electric field, total treatment time or pulse frequency the higher the degree of PME inactivation from all sources. Maximum enzyme inactivation was: 87% for orange and tomato PME, 83% for carrot PME and 45% for banana PME at the most intense conditions. (c) 2005 Elsevier Ltd. All rights reserved.