University of Kentucky UKnowledge University of Kentucky Master's Theses Graduate School 2007 CHARACTERIZATION OF POLYPHENOL OXIDASE AND ANTIOXIDANTS FROM PAWPAW (ASIMINA TRIBOLA) FRUIT Caodi Fang University of Kentucky,
[email protected] Right click to open a feedback form in a new tab to let us know how this document benefits ou.y Recommended Citation Fang, Caodi, "CHARACTERIZATION OF POLYPHENOL OXIDASE AND ANTIOXIDANTS FROM PAWPAW (ASIMINA TRIBOLA) FRUIT" (2007). University of Kentucky Master's Theses. 477. https://uknowledge.uky.edu/gradschool_theses/477 This Thesis is brought to you for free and open access by the Graduate School at UKnowledge. It has been accepted for inclusion in University of Kentucky Master's Theses by an authorized administrator of UKnowledge. For more information, please contact
[email protected]. ABSTRACT OF THESIS CHARACTERIZATION OF POLYPHENOL OXIDASE AND ANTIOXIDANTS FROM PAWPAW (ASIMINA TRIBOLA) FRUIT Crude polyphenol oxidase (PPO) was extracted from pawpaw (Asimina triloba) fruit. The enzyme exhibited a maximum activity at pH 6.5–7.0 and 5–20 °C, and had -1 a maximum catalysis rate (Vmax) of 0.1363 s and a reaction constant (Km) of 0.3266 M. It was almost completely inactivated when incubated at 80 °C for 10 min. Two isoforms of PPO (MW 28.2 and 38.3 kDa) were identified by Sephadex gel filtration chromatography and polyacrylamide gel electrophoresis. Both the concentration and the total activity of the two isoforms differed (P < 0.05) between seven genotypes of pawpaw tested. Thermal stability (92 °C, 1–5 min) and colorimetry (L* a* b*) analyses showed significant variations between genotypes.