Inactivation of Apple Pectin Methylesterase Induced by Dense Phase Carbon Dioxide
2008
Zhi, X. | Zhang, Y. | Hu, X. | Wu-O, Jess | Liao, X.
The inactivation of apple pectin methylesterase (PME) with dense phase carbon dioxide (DPCD) combined with temperatures (35-55 °C) is investigated. DPCD increases the susceptibility of apple PME to the temperatures and the pressures have a noticeable effect on apple PME activity. A labile and stable fraction of apple PME is present and the inactivation kinetics of apple PME by DPCD is adequately described by a two-fraction model. The kinetic rate constants kL and kS of labile and stable fractions are 0.890 and 0.039 min-1, and the decimal reduction times DL and DS are 2.59 and 58.70 min at 30 MPa and 55 °C. ZT representing temperature increase needed for a 90% reduction of the D value and the activation energy Ea of the labile fraction at 30 MPa is 22.32 °C and 86.88 kJ /mol, its ZP representing pressure increase needed for a 90% reduction of the D value and the activation volume Va at 55 °C is 21.75 MPa and -288.38 cm3/mol. The residual activity of apple PME after DPCD exhibits no reduction or reactivation for 4 weeks at 4 °C.
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