大根の真空調理に伴う品質変化

抄録

Quality changes in vacuum-packaged Japanese radish during cooking were studied in relation to the difference of cooking temperatures (65,70,80 or 100°C) and the degree of vacuum (30 or 100Torr) in packaging. The cooking of Japanese radish packaged under reduced and normal pressures and the non-packaged cooking were used as cooking methods.
Japanese radish was softened in the cooking at 70°C or higher temperatures, but not completely softened at 65°C. Japanese radish cooked at 100°C or 80°C showed no changes in surface colour. However, at 70°C, browning occurred in the cooking of Japanese radish packaged under normal and 100 Torr pressures, but not 30 Torr pressure and in the non-packaged cooking.
There were no apparent differences observed in the hardness of Japanese radish and the degree of vacuum during cooking at 70 or 80°C. However Japanese radish remained hard with lowering of the degree of vacuum and hardest under the normal pressure at 100°C.
The content of total ascorbic acid in Japanese radish showed no difference with the change of vacuum at 100°C. On the other hand, in the cooking at the temperature below 100°C, the content of Japanese radish packaged at 30 Torr showed a higher content of ascorbic acid than that of the usual cooking. The higher the degree of vacuum was, the lower dehydroascorbic acid content became at 100°C.
There were no considerable differences between sugar content and the degree of vacuum in the cooking of packaged Japanese radish. However, the sugar content of the usual cooking was lower as compared with that of the cooking of packaged Japanese radish at all the temperatures.
These results described here indicate that the cooking at 80°C or higher temperatures and under reduced pressures is better for keeping quality of Japanese radish.