ศูนย์นวัตกรรมเทคโนโลยีหลังการเก็บเกี่ยว

Effect of pH on pressure and thermal inactivation of avocado polyphenol oxidase: a kinetic study.

Carla A. Weemaes, Linda R. Ludikhuyze, Ilse Van den Broeck and Marc E. Hendrickx

Journal of Agricultural and Food Chemistry. Volume 46, Number 7, July 1998. Pages 2785-2792.

1998

บทคัดย่อ

High-pressure and thermal inactivations of avocado polyphenol oxidase (PPO) were studied for enzyme systems with pH 4-8. Both pressure and temperature inactivation of the enzyme followed first-order kinetics in the pH range 5-8 but showed deviation from simple first-order kinetics at pH 4. Threshold pressure and temperature for PPO inactivation, as well as pressure and temperature dependence of the inactivation rate constants, were influenced by pH. The minimum inactivation pressure increased from approximately 450 MPa at pH 4 to approximately 850 MPa at pH8. The threshold temperature increased from approximately 40 at pH to approximately 65 degrees C at pH 6 and was approximately constant at higher pH values. The z(p) value and the absolute value of the activation volume both reflecting the pressure dependency of the inactivation rate constant, respectively increased and decreased with increasing pH, in the pH range 5-8. The z(t) value and activation energy, both reflecting the temperature dependency of the inactivation rate constant, respectively decreased and increased with increasing pH in the pH range 5-7. At pH 8, the activation energy was slightly lowered.