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KMID : 0903620010420020184
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Journal of the Korean Society for Horticultural Science
2001 Volume.42 No. 2 p.184 ~ p.188
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Changes of Phenolic Compounds and Occurrence of Skin Browning , and Characterization of Partially Purified Polyphenol Oxidases in Oriental Pear Fruits
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Lim Yeoun-Su
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Abstract
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The major phenolics found in oriental pears were chlorogenic acid followed by epicatechin and 4-hydroxymethyl benzoic acid in general. Other phenolics were also detected at a relatively low level. Both the levels of total phenolic content and chlorogenic acid significantly decreased during storage in skin browning sensitive cultivar ´Niitaka´ but this trend was not found in ´Kamchun´ pears which is tolerant. Fruit suffered from skin browning contained less amount of total phenolics and chlorogenic acid but the activity of polyphenol oxidase (PPO) was significantly higher compared to sound fruit. Three isozymes of PPO were found through DEAE-cellulose chromatography in ´Niitaka´ pears. Maximum reaction rates of the respective isozymes were at pH 7.0 and 30℃ for PPO C, pH 5.5 and 40℃ for PPO A, and pH 7.5, and 30℃ for PPO B. And there was difference in substrate specificity between isozymes, thus, PPO A showed relatively higher specificity to epicatechin, B and C to chlorogenic acid. Also, the activities of isozyme B and C were remained at high level even at low temperature. Results indicated that the oxidation of chlorogenic acid by PPO B and C is strongly involved with the incidence of skin browning in oriental pears.
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