54F-10

P. S. TAOUKIS, G. Katsaros, P. Katapodis, and S. Boulekou. School of Chemical Engineering, National Technical Univ. of Athens, Iroon Polytechniou 5, Athens, 15780, Greece

Pectin methylesterase (PME) can be found in significant levels of activity in various fruits and vegetables such as orange, tomato, peach and persimmon. The cloud loss of juices is mainly attributed to the action of PME. HHP inactivates PME while maintaining the quality characteristics of the fruit juices, resulting in products of superior quality. Considerable research has been reported on PME inactivation by HHP. The specific origin of the enzyme affects the inactivation behavior as shown in previous studies for PMEs of different sources. The objective of this work was to study and model the effect of HHP processing on the inactivation of PME obtained from fresh peach and persimmon pulps. The effect of High Hydrostatic Pressure (100-800 MPa) combined with moderate temperature (30-60^o C) on the inactivation of PME was investigated. A multivessel HPP unit allowed the study of PME activity decrease as a function of time at different sets of pressure and temperature conditions. Inactivation at atmospheric pressure at 50 to 90^o C was also tested. The inactivation of both PMEs followed first order kinetics. The rate constants at each temperature and pressure condition were calculated. The activation energy E_a, as well as the activation volume V_a were estimated as a function of pressure and temperature respectively. The developed kinetic models, having as variables time, pressure and temperature, allows the calculation of remaining activity at any combination of processing conditions within the studied domain. The PME inactivation results of PME obtained from these two sources showed that the kinetics depended on the source of the enzyme. In order to achieve an optimal process design, a systematic study of PME inactivation for the specific system is necessary as evidenced from the results. The developed kinetics allow the selection of optimal HHP process conditions for achieving the desirable PME inactivation in the target products.

Session 54F, Nonthermal Processing: General I
2:00 PM - 5:30 PM, Monday PM Room Hall I-2

2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana