Abstract
This study was performed to know the relation between changes of components of Japanese radish and changes of its crisp palatability in the manufacturing processes of pickled one (takuan zuke). Changes of carbohydrates of Japanese radish, especially pectin and activities of some enzymes related to their degradation in the first ten days of the salting were investigated. The results obtained were as follows:
1. Moisture was decreased and ash was increased during this period. But the amounts of crude fiber, crude fat, crude protein, nitrogen-free extract, starch, pectin, soluble total sugar and reducing sugar were hardly changed.
2. Main components of the radish pectin were soluble ones in 0.5% ammonium oxalate and 0.05N hydrochloric acid. It was observed that the former was decreased and the latter was increased during the salting.
3. Polygalacturonase activity was decreased and could not be detected after 3 days of the salting. α-Amylase activity was not changed.
4. Pectin methylesterase activity was markedly increased after 2 days of the salting and quickly decreased after 5 days. Methoxyl contents in radish pectins were decreased and this tendency was notable in 0.05N hydrochloric acid soluble-pectin.
5. By chromatography of 0.05N hydrochloric acid-soluble-pectin on DEAE-cellulose, the retention volume of pectin from the 10 days salted radish needed more 50ml than that from the fresh radish by 50ml.
6. Viscosity of 0.05N hydrochloric acid soluble pectin was markedly increased.
7. Calcium content was increased.
From these results, it was presumed that the increase of viscosity of the radish pectin along with the decrease of methoxyl group content and the increase of the degree of cross-linkage of the pectin resulting from the increase of calcium content were causes of the change of the crispness of the Japanese radish during the salting.
