Serine protease inhibitors from squid ovary: extraction and its effect on proteolysis and gel properties of surimi

Abstract

Serine protease inhibitors from squid ovary (SOSPI) were extracted using different extraction media and conditions. Optimal condition included 0.45 M NaCl for 1 h. After heat treatment at 70°C for 10 min, the highest specific activity was obtained. Based on Sephadex G-75 gel filtration and activity staining, the major SOSPIs were present as monomer with molecular weight of 9.10 and 10.27 kDa. Impact of SOSPI on autolysis of bigeye snapper surimi was studied. Myosin heavy chain was more retained with coincidentally lower trichloroacetic acidsoluble peptide content as the level of SOSPI increased. When SOSPI at various levels (0.5-3%) was added into surimi, the highest breaking force of both kamaboko and modori gels containing 1% SOSPI was obtained. However, SOSPI had no effect on deformation of kamaboko gel but slightly increased the deformation of modori gel. SOSPI increased water holding capacity of both kamaboko and modori gels in a dose dependent manner, as indicated by the lowered expressible moisture content. SOSPI had no effect on the whiteness of both gels. Thus SOSPI can be used as the protein additive in surimi for increasing breaking force.

Proteolysis and Its Control Using Protease Inhibitors in Fish and Fish Products: A Review

“…In WPC, an unidentified PI with an apparent MW of 101 kDa was detected and exhibited inhibitory action against papain and trypsin (Weerasinghe, Morrissey, Chung, & An, ). Recently, Singh and Benjakul () extracted and partially purified a serine PI from squid (Loligo formosana ) ovary.…”

“…The total inhibitor activity and specific activity were increased by 58% and 62%, respectively, when the defatted roe was extracted using 10 mM phosphate buffer (pH 7) as the medium. Recently, a serine PI was retrieved from squid ovary using 0.45 M NaCl for 1 hr, and it exhibited the maximal specific inhibitory activity compared to the water extract (Singh & Benjakul, ). It has been demonstrated that chloride ions increase the solubility of PIs, by enhancing the electrostatic repulsion after binding to the positively‐charged groups of the protein (Singh & Benjakul, ).…”

“…Recently, a serine PI was retrieved from squid ovary using 0.45 M NaCl for 1 hr, and it exhibited the maximal specific inhibitory activity compared to the water extract (Singh & Benjakul, ). It has been demonstrated that chloride ions increase the solubility of PIs, by enhancing the electrostatic repulsion after binding to the positively‐charged groups of the protein (Singh & Benjakul, ). When extraction time exceeded the optimal, protein content in the extract from squid ovary was increased, resulting in a diminished specific activity (Singh & Benjakul, ).…”

“…It has been demonstrated that chloride ions increase the solubility of PIs, by enhancing the electrostatic repulsion after binding to the positively‐charged groups of the protein (Singh & Benjakul, ). When extraction time exceeded the optimal, protein content in the extract from squid ovary was increased, resulting in a diminished specific activity (Singh & Benjakul, ).…”

Comparative study on the effect of duck and hen egg albumens on proteolysis and gel property of sardine surimi

“…[21] Five cylindrical samples were cut into 2.5 cm height and 2.5 cm diameter and equilibrated at room temperature (25°C-28°C) before analyses. Sample was perpendicularly pressed by a spherical plunger of 5 mm diameter into the cut surface of gel at a constant depression speed (60 mm/min).…”