Stabilization and partial purification of a protease from ginger rhizome (Zingiber offinale Roscoe)

Ginger protease (GP) or zingibain is of interest as a meat tenderizing agent. The objective of this research was to investigate food-compatible methods for stabilizing GP during storage or enzyme fractionation. Crude GP extracted from fresh ginger had a half-life (t(1/2)) of 2.1 (+/- 0.16) d at 5 degrees C decreasing to 20 min at 30 degrees C. Addition of ascorbate (0.2% w/v) increased the t(1/2) for GP from 2 to 20 d at 5 degrees C. Dithiothreitol or Ethylenediaminetetraacetic acid (EDTA) had no effect on GP stability. Acetone powder preparations from ginger yielded GP with t(1/2) of 18 mo at 5 degrees C. Crude GP extracted from acetone powder was sufficiently stabilized to allow fractionation by ion exchange chromatography without the addition of toxic or expensive additives. GP was partially purified 252-fold with a recovery of 61%. The nomimal molecular weight of GP was 34.8 kDa compared with 25.1 kDa for papain. This work shows that the stability of GP can be greatly improved, increasing its attractiveness as a commercial product. Some possible routes of GP deactivation and stabilization are discussed.