スケトウダラの坐りにおけるミオシンの酵素架橋重合に及ぼす塩の影響

Abstract

Salted surimi pastes were prepared either with each of NaCl, KCl, and NH4Cl, or with a mixture of the two salts at pH 7.0 and a constant ionic strength (I=0.6) in the presence or absence of monodansyl cadaverine (MDC). They were incubated at 25°C for several hours (suwari gel) and then heated at 90°C for 20 min (cooked gel). The gels produced were analyzed by measuring the breaking strength and amounts of cross-linked myosin heavy chain and incor-porated MDC as a probe of transglutaminase activity. The breaking strength of the directly heated gels containing NaCl and KCl at various ratios was almost constant, whereas those of the suwari and cooked gels increased in propor-tion to the increasing ratio of NaCl to KCl. A similar NaCl-dependent increase was found in the amounts of cross-linked myosin heavy chain and incorporated MDC. The breaking strength of suwari and cooked gels was strongly depressed by a small amount of NH4Cl (in the mM range) contained in NaCl at a total ionic strength of I=0.6 with a con-comitant decrease in the amounts of cross-linked myosin heavy chain and incorporated MDC.