Changes in chemical composition and peroxidase activity of turnip (Brassica rapa) during processing and frozen storage

Chemical composition content and peroxidase enzyme activity of raw, canned and frozen turnip roots were determined. The peroxidase activity determined in the roots of raw turnip was 134x105 EU/100 g fresh weight and 170x105 EU/g protein. There were significant changes in the activities of peroxidase of canned and frozen turnip roots, as well as in the contents of protein. The peroxidase activity of canned turnip roots was practically undetectable while there was residual activity after blanching and freezing. Peroxidase is one of the most heat-stable enzymes in plants. This study shows that heat treatment of 3 min at 95°C is preferred for POD activity inactivating compared with other heat treatment. In addition, conserving process inactivated of POD activity, too.