الفهرس 
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Abstract
The browning of peaches during preparation for processing
and frozen storage is a serious and costly problem. The process is considered to be enzymatic in nature and due to the oxidation of phenolic compounds by oxidizing enzymes in the presence of molecular oxygen.
This study was conducted to investigate the relationships between the enzyme system and the substrates responsible for bringing about brown discoloration in freestone peaches. The enzyme, polyphenol oxidase (PPO), was prepared by acetohe precipitation and purified by ammonium sulfate fractionation and Sephadex G-l00. The enzyme solution was jnjt stable at pH 8.0 at all the temperatures used, from 220 to 31.7 C. The enzyme was not very stable at room temperature, 22° C., losing 93.3% of its activity in 6 days. The frozen solutions stored for 12 weeks at -17.8° C. and -31.7° C. showed a loss in activity of 20 and 16. 6%, respectively.