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

The inhibitory activities of pig plasma protein (PPP) against proteinases a nd autolysis were studied. Using casein as a substrate, it was shown that P PP exerted inhibitory activity against Pacific whiting (PW) proteinase, pap ain and trypsin. At levels of 10 and 20 mg ml(-1), PPP showed higher inhibi tory activity than beef plasma protein (BPP) or egg white against PW protei nase (P < 0.05). The inhibitory activity was proportional to the concentrat ion 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 show ed lower inhibition than PPP or BPP against autolysis of surimi (P < 0.05). Myosin heavy chain (MHC) in Pacific whiting surimi was better retained whe n higher concentrations of PPP were used, while no changes in actin were ob served. Inhibitory activity staining on sodium dodecyl sulphate (SDS) subst rate gels incubated with papain or trypsin indicated that residual protein bands with apparent molecular weights of 60 000-63 000 may be the active in hibitory components in PPP. These bands were found in PPP and bovine plasma fraction IV-1, although only under non-reducing conditions. (C) 2000 Socie ty of Chemical Industry.