Thermostability and freeze denaturation of grass prawn (Penaeus monodon) muscle proteins

The thermostability of actomyosin (AM) and freeze denaturation of muscle proteins from grass prawn were investigated. A comparison of the inactivation rate constant (KD) of AM Ca-ATPase at 0-45 degrees C showed that thermostability of AM decreased with an increase of incubation temperature. From the Arrhenius plot of KD, the AM at zone I (0-25 degrees C) was more stable than at zone II (25-45 degrees C). The AM was stable around pH 7.6, which was almost the same as for other shellfishes. The stability of KD at 35 degrees C of this species was lower than that of milkfish, tilapia hybrid, tilapia, and carp. Except for the extractable AM, the total SH and Ca-ATPase activity of AM decreased significantly immediately after freezing and further decreased during 6 months of frozen storage at -10, -20, -30, and -40 degrees C (p 0.01). The KD lowered as frozen storage temperature decreased; however, there was no significant difference between -30 and -40 degrees C (p 0.01)