Graduate Thesis Or Dissertation
 

Isolation and characterization of some oxidizing enzymes of the McFarlin cranberry

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  • Due to the scarcity of information concerning the oxidase systems in cranberries the peroxidase, catalase, and polyphenolase systems, which are used as biochemical indexes of adequacy for enzyme inactivation in other fruits and vegetables, were investigated. Enzyme extracts were prepared from acetone powders with and without phenol-binding agents such as polyethylene glycol and polyvinylpyrrolidone (PVP) and buffered PVP. The acetone-PVP combination was found to be the most effective in reducing the polyphenolic content of the enzyme extract. Highest specific activity was obtained by using a buffered PVP extract. The pH optimum of cranberry peroxidase activity is 6.0. Heat inactivation of cranberry peroxidase was determined to follow first order kinetics. There was 90% destruction at 70, 80, and 90°C requiring 9.40, 1.60, and 0.47 minutes of heat treatment, respectively. The activation energy for the thermal inactivation of cranberry peroxidase was found to be 37.2 kcal/mole. Guaicol, o-phenylene diamine (OPDA), and pyrogallol were tested for their sensitivity to cranberry peroxidase with OPDA determined as most sensitive. The pH optimum for catalase activity was found to range from 7.5 to 9.2. Kinetics for the heat inactivation of cranberry catalase was determined not to be of the first order nor zero order. Approximately 50% of the catalase activity is inactivated after heating for 17, 1.8, and O.6 minutes at temperatures of 50, 60, and 70°C, respectively. Cranberry polyphenolase activity was measured using catechol as a substrate. The product of the reaction absorped maximally at 400 mu. The pH optimum for cranberry polyphenolase activity was determined to be 7.0. Heat inactivation of cranberry polyphenolase was found to follow first order kinetics. There was 90% destruction at 50, 60, and 70°C requiring 15.85, 7.05, and 1.37 minutes of heat treatment, respectively. The activation energy for the inactivation of cranberry polyphenolase was found to be 27.7 kcal/mole.
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