Heat Inactivation Kinetics of Apple Polyphenoloxidase and Activation of its Latent Form

Authors

  • AHMET YEMENICIOĞLU,

    1. Authors Yemenicioglu and Ózkan are graduate students, and author Cemeroglu is a professor, Faculty of Agriculture, Dept. of Food Engineering, Ankara Univ., Dişkapi-Ankara 06110, Turkey.
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  • MEHMET ÖZKAN,

    1. Authors Yemenicioglu and Ózkan are graduate students, and author Cemeroglu is a professor, Faculty of Agriculture, Dept. of Food Engineering, Ankara Univ., Dişkapi-Ankara 06110, Turkey.
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  • BEKIR CEMEROĞLU

    1. Authors Yemenicioglu and Ózkan are graduate students, and author Cemeroglu is a professor, Faculty of Agriculture, Dept. of Food Engineering, Ankara Univ., Dişkapi-Ankara 06110, Turkey.
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ABSTRACT

Heat inactivation kinetics of crude polyphenoloxidase (PPO) from six apple cultivars (Golden Delicious, Starking Delicious, Granny Smith; Gloster, Starcrimson and Amasya) were studied at three temperatures (68°, 73° and 78°C). PPO activity initially increased and then decreased with heat, following a first order kinetic model. Increase in activity indicated presence of latent PPO. Regression coefficients for the linear portions of inactivation curves were computed to determine inactivation parameters. Reaction data at 78°C revealed that PPO in Amasya was the least and Starking Delicious the most heat-stable. Rate constants for heat inactivation at 78°C ranged from 15.99–28.27. 10−2 min−1. Activation energies varied between 54.7–77.2 kcal. mol−1 with z values of 7.1–10.0C°.PPO in apples was generally more heat-stable than PPO in most fruits.

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