Characterization of active components in food-grade proteinase inhibitors for surimi manufacture

Commonly used food-grade inhibitors, beef plasma protein (BPP), egg white, and potato powder, were characterized for their inhibitory activity toward proteinases. BPP and egg white had the highest rate of cysteine and serine proteinase inhibition, respectively. Egg white, containing specific serine proteinase inhibitors, reduced trypsin activity by as much as 99%. Active inhibitory components in the proteinase inhibitors were detected by inhibitory activity staining on sodium dodecyl sulfate (SDS)-substrate gels. Egg white and potato powder contained more serine proteinase inhibitor bands than cysteine proteinase inhibitor bands. No specific cysteine proteinase inhibitory component was found in BPP. Serum albumin was detected on both papain and trypsin inhibitory activity-stained gels of BPP but was not inhibitory to the proteinases. A high molecular weight protein band (HMP) of BPP was also detected on both inhibitory activity-stained gels, but the protein was postulated to be polymerized plasma components resistant to proteolysis.