Gi-Nahm Kim

Prevention of Browning in Potato with a Heat-treated Onion Extract

The inhibitory effect of an onion extract on browning of potato was investigated. The addition of the heated onion extract to potato exhibited a marked inhibitory effect on potato polyphenol oxidase and the formation of a brown color. The inhibitory effect of the onion extract was dependent upon its heating temperature. The addition of both glycine and glucose increased the inhibitory effect of the onion extract toward potato polyphenol oxidase.

Acid and Heat Stability of the Anticoagulative Activity of an Onion Extract

An onion extract possessed anticoagulative activity apparently by inhibiting thrombin, and it was dependent upon the concentration of onion extract added. Boiling the onion extract at 100°C for 30 min made no difference to its anticoagulative activity compared to that of fresh onion. The anticoagulative activity of the onion extract was also retained after an acid treatment by incubating at pH 2.0 for 4 hrs. However, dialyis of the extract substantially eliminated the anticoagulative activity. Therefore, the anticoagulant in the onion extract seems to have been a heat- and acid-stable substance of low molecular weight.

The Novel Assay Method for Thrombin by Weighing Fibrin Clot

This study was performed to establish a simple and rapid method for measuring thrombin activity based on weight of fibrin clot formed. The new method was based on the weight measurement of fibrin clot after enzymatic reaction of thrombin with fibrinogen. The fibrin formation depended upon the activities of thrombin used, temperature, incubation time, and centrifugation time. The fibrin formation was increased proportionally up to 1.0 unit/ml of thrombin activity, 4.0mg/ml of fibrinogen concentration, and 5 min of incubation time at 37. The fibrin clot formed was stable by centrifugation at 3,000g for 5min. This simple assay based on weight of fibrin after centrifugation would be useful for identifying natural food anticoagulants by inhibiting thrombin.