Abstract
ortho-Diphenol compounds, such as chlorogenic acid, caffeic acid and catechin, are closely related to enzymatic browning in plant foods. A spectrophotometric assay of chlorogenic acid oxidase was performed on the basis of difference spectra. An enzyme solution prepared from seeds of sweet pepper (Capsicum annuum L.) was used. The enzyme showed a strong activity for chlorogenic acid oxidation at about pH 4 and was inactivated at a pH of less than pH 2. As enzymatic oxidation proceeded, a negative peak in the difference spectra appeared at 325 nm. The peak height (_??_E325) reached maximum after 5min and did not vary for about 60min. The _??_E value was directly proportional to the concentration of chlorogenic acid. Therefore, the content of chlorogenic acid in food was estimated by measuring the _??_E value. Several sample solutions were analyzed by this method and by the Zucker and Ahrens colorimetric method based on the Hoepfner reaction. Highly accurate results were obtained by our method and the recovery was quite good.
