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Browning |
Walker (1962) measured actual and potential browning in apples. Potential browning was determined by adding excess substrate to avoid a limiting-substrate factor. He stated that the degree of browning was related to the content of chlorogenic acid, which Bradfield et al. (1952) reported to be the phenolic substrate for polyphenol oxidase in apples. Guadagni et al. 91949) reported a linear relationship between the amount of oxidizable phenols and change in optical density of the filtrate of frozen peaches. Less than half of the oxidizable phenols reminaed after the peach filtrate had been allowed to brown for 15 minutes, and browning no longer occurred at a rate proportional to the original activity of the enzyme. Guadagni et al. concluded that total browning at the end of 60 minutes was more dependent on the original phenolic content than on enzyme activity.
Weurman and Swain (1955) reported that browning in apples decreased 75 percent during the period of ripening from 37 days to 170 days from petal drop, but they concluded that activity of the enzyme was a more important factor than concentration of phenolic substances. Harel et al. (1966) contended that both enzyme and substrate are factors influencing extent of browning. Because the concentration of both substrate and enzyme changes as the fruit develops, their relative importance probably changes also.
Updated: Wednesday, June 20, 2007.
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