Pig plasma protein: potential use as proteinase inhibitor for surimi manufacture; inhibitory activity and the active components

Abstract

The inhibitory activities of pig plasma protein (PPP) against proteinases and autolysis were studied. Using casein as a substrate, it was shown that PPP exerted inhibitory activity against Pacific whiting (PW) proteinase, papain and trypsin. At levels of 10 and 20 mg ml−1, PPP showed higher inhibitory activity than beef plasma protein (BPP) or egg white against PW proteinase (P < 0.05). The inhibitory activity was proportional to the concentration of PPP used up to 10 mg ml−1. PPP and BPP showed marked inhibition of autolysis of PW surimi at concentrations of 10–30 mg g−1. Egg white showed lower inhibition than PPP or BPP against autolysis of surimi (P < 0.05). Myosin heavy chain (MHC) in Pacific whiting surimi was better retained when higher concentrations of PPP were used, while no changes in actin were observed. Inhibitory activity staining on sodium dodecyl sulphate (SDS) substrate gels incubated with papain or trypsin indicated that residual protein bands with apparent molecular weights of 60 000–63 000 may be the active inhibitory components in PPP. These bands were found in PPP and bovine plasma fraction IV-1, although only under non-reducing conditions. © 2000 Society of Chemical Industry