Biochemical characterization and process stability of polyphenoloxidase extracted from Victoria grape (Vitis vinifera ssp. Sativa) |
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| Authors: | Gabriela Rapeanu Ann Van Loey Chantal Smout Marc Hendrickx |
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| Affiliation: | 1. Department of Bioengineering, Faculty of Food Science and Engineering, “Dunarea de Jos” University, Domneasca 111, 800201 Galati, Romania;2. Laboratory of Food Technology, Department of Food and Microbial Technology, Faculty of Agricultural Applied Biological Sciences, Katholieke Universiteit Leuven, Kasteelpark Arenberg 22 B-3001 Heverlee-Leuven, Belgium |
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| Abstract: | Polyphenol oxidase (PPO) was isolated from Victoria grapes (Vitis vinifera ssp. Sativa) grown in South Africa and its biochemical characteristics were studied. Optimum pH and temperature for grape PPO activity were pH 5.0 and T = 25 °C with 10 mM catechol in McIlvaine buffer as substrate. PPO showed activity using the following substances: catechol, 4 methyl catechol, d, l-DOPA, (+) catechin and chlorogenic acid. Km and Vmax values were 52.6 ± 0.00436 mM and 653 ± 24.0 OD400 nm/min in the case of 10 mM catechol as a substrate. Eight inhibitors were tested in this study and the most effective inhibitors were found to be ascorbic acid, l-cysteine and sodium metabisulfite. Kinetic studies showed that the thermal inactivation of Victoria grape PPO followed first-order kinetics, with an activation energy, Ea = 225 ± 13.5 of kJ/mol. Both in semipurified extract and in grape juice, PPO showed a pronounced high pressure stability. |
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| Keywords: | Grape Vitis vinifera ssp Sativa Polyphenoloxidase Characterisation Thermal and high pressure stability |
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