1985 Volume 54 Issue 1 Pages 109-115
Extensive browning due to rind-oil spot was found in peels of Murcott(Citrus reticulata×Citrus sinensis) and Funadoko(Citrus funadoko hort. ex. Y. Tanaka) which were stored for three months at room temperature. Absorption spectra and difference spectra of extracts of injured and healthy sections of these fruit peels were measured. In Murcott, the difference spectra of these extracts showed a negative peak at 325nm and were in good agreement with spectra obtained when extracts of healthy sections were oxidized by polyphenol oxidase. Similar difference spectra were found in the enzymatic oxidation of chlorogenic acid. Chromatographic determination indicated that the extract of healthy sections contained chlorogenic acid analogues, but the analogues were not detected in the extracts from injured sections. In Funadoko, the difference spectra of the extracts of healthy and injured sections showed negative peaks at 325nm and 265nm. The peak at 325nm was similar to that found in Murcott peel extract. The peak at 265nm was also found in difference spectra obtained when extracts from healthy sections were oxidized by ascorbic acid oxidase, and the spectra were in good agreement with those for the enzymatic oxidation of L-ascorbic acid.
From the above results, it seems that the oxidation of chlorogenic acid analogues and L-ascorbic acid plays an important role in the browning due to rind-oil spot.