Proteinase inhibitory activity of sarcoplasmic proteins from threadfin bream (Nemipterus spp.)

Abstract

Thailand is the second largest surimi producer in the world and 50% of surimi is produced from threadfin bream. During surimi processing, sarcoplasmic proteins are removed through water washing and discarded in the waste stream. This study was aimed at investigating the proteinase inhibitory activity of sarcoplasmic proteins. Sarcoplasmic proteins from threadfin bream (TBSP) exhibited inhibitory activity toward trypsin but did not inhibit papain and chymotrypsin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis under non-reducing condition stained by trypsin inhibitory activity revealed three protein bands of molecular mass of 95, 41 and 37 kDa. Inhibitory activity of TBSP reached a maximum when subjected to 45 degrees C and completely disappeared at 60 degrees C. The breaking force and deformation of lizardfish surimi gel with added TBSP and pre-incubated at 37 degrees for 20 min increased with additional levels of TBSP (P < 0.05). Trichloroacetic acid-oligopeptide content of lizardfish surimi gel with added TBSP decreased with the addition of 4 g kg(-1) TBSP (P < 0.05). Retention of myosin heavy chain (MHC) increased when TBSP concentration was increased. TBSP effectively protected MHC from proteolysis at 37 degrees C to a similar extent as egg white powder, but efficacy of TBSP was not observed at 65 degrees C. TBSP could be applied to reduce proteolytic degradation of lizardfish surimi or other surimi associated with trypsin-like proteinase, rendering an improvement in surimi gelation set at 37-40 degrees C.