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KMID : 1007519960050020152
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Food Science and Biotechnology
1996 Volume.5 No. 2 p.152 ~ p.155
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Rapid Measurement of the Enzymatic Browning of Pear Juice by the Addition of L - DOPA
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Kim, Woo Yeon
Hwang, In Gil/Yoon, Kwang Ro
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Abstract
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Discoloration of pear juice is caused by the action of polyphenol oxidase in pear and chemical browning reactions. The objective of this study was to establish a method to assess the potential for the discoloration in pear juice during processing and storage. The pear extracts tested in this experiment did not show the enzymatic or nonenzymatic discoloration for 48 hr at 4℃. However, the enzymatic browning of pear extracts was triggered rapidly in the presence of 9.3 mM L-DOPA (3,4-dihy-droxyphenylalanine). The triggered browning reactions of pear extracts in the presence of L-DOPA were inhibited not only by the addition of ascorbic acid to 0.2 mM but also by the adjustment of pH to 3. Pear pulp including the flesh and stone cells showed higher polyphenol oxidase activity, whereas pear epidermis layers seemed to contain more phenolic compounds. Therefore, removal of epidermis layers might be helpful for the additional reduction of the discoloration of pear extracts.
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