Abstract
In order to get a clue explaining the change of the absorption spectrum of apple juice due to browning, spectra were determined on a model system of apple enzyme and pyrogallol, catechol or chlorogenic acid. In the case of pyrogallol, 2 shoulders at 275mμ and 370mμ and smaller one at 420mμ were observed at the first stage and then flattened except that at 275mμ. However, the maximum increase of the optical density was observed at 300mμ throughout the reaction. With catechol, distinct peak was formed between 380mμ and 390mμ in a short time, probably dependent to quinone forming, and then diminished. However, the peak of catechol at 275mμ was changed into shoulder. Thus, the change of the optical density having the maxima at 290mμ and 250mμ and the minimum at 275mμ was observed, although the peak at 380mμ had been seen in the beginning of the browning. In the case of chlorogenic acid, the peak was first formed at 400mμ and then flattened. The maximum increase of the optical density was determined at 400mμ which was then moved to 380mμ. Incidentally, in the UV range, 2 peaks of chlorogenic acid at 325mμ and 293mμ were disappeared and the new one was formed at 250mμ which was decreased again. Thus, the highest increase of the optical density was observed at 260mμ and the maximum decrease at 300mμ. By comparing the changes of these spectra, it was suggested that the browning of apple juice, at least, could not be attributed only to chloragenic acid.
