Major phenolic compounds of white grapes grown in New York were isolated individually, and polyphenoloxidase was added to each to measure their relative rates of browning (A420nm) in a model system. A browning index (BI) was established for individual phenolic compounds, such as cis- and trans-isomers of caffeoyl and coumaroyl tartrates, catechin, epicatechin, procyanidin B2 and B3, catechin-gallate, and catechin-catechin-gallate, based on their maximum absorbances, and then the browning potential (BP) values for each grape cultivar were calculated. For some grape cultivars, there was a high correlation between calculated BP values and the observed degree of browning.
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Lee et al. (1988) studied this question.