Cysteine proteinase inhibitor from chicken plasma: Fractionation, characterization and autolysis inhibition of fish myofibrillar proteins

Cysteine proteinase inhibitor (CPI) from chicken plasma was fractionated by using polyethylene glycol (PEG-4000) or ammonium sulfate (AS). Addition of PEG, at the level of 200–400 g/l based on the original volume of plasma protein, was more effective to fractionate CPI than was using AS. Highest inhibitory activity and purification-fold were obtained in the PEG precipitate II (CPI fraction). The CPI fraction was stable in the temperature ranges of 40–90 °C for 10 min but extended incubation time at 90 °C markedly decreased the inhibitory activity of the CPI fraction. The fraction was stable in the broad pH ranges tested (3–10). NaCl concentrations of 0.5–3% did not affect the inhibitory activity of the CPI fraction. The CPI fraction effectively prevented the degradation of mince and washed mince from Pacific whiting; however, lower efficacy in inhibiting autolysis of the arrowtooth flounder mince and the washed mince was observed, suggesting differences in initial proteolytic activity between the two species. Therefore, the CPI fraction from chicken plasma could be an alternative food grade inhibitor for the surimi industry.