Chicken egg white is generally used in the industry because of its excellent effect to improve physical property of surimi products. The effects of egg white are believed to be derived from its inhibitory activity on surimi endogenous proteases which reduce gel forming ability. However, there are no detailed investigations about inhibitory effects of egg white on the proteases. The effect of ovalbumin (OVA), which is the main protein of egg white, on trypsin activity was investigated in the present study. N-OVA was purified from fresh chicken egg white by ammonium sulfate fractionation and anion-exchange chromatography (Q-sepharose). S-OVA and I-OVA were prepared by heating N-OVA solution at pH10, 55°C for 24h and at 97°C for 30min (pH was not controlled) respectively. To investigate the effect of OVA on the trypsin activity, casein-trypsin mixture solution was heated with or without OVAs at 40°C and the content of peptide generated from casein was measured. SDS-PAGE of casein was also conducted. The amount of peptide from casein was decreased in the presence of OVAs, regardless of OVA types. SDS-PAGE showed all types of OVA inhibited casein degradation. Those suggest that all types of OVA have inhibitory effect on the trypsin activity.
Keywords : Surimi, Ovalbumin, Proteases, Egg white