Change of muscle proteins in Nile tilapia fillets during iced storage

We extracted different solubility proteins and structure proteins from Nile tilapia (Oreochromis niloticus) fillets during iced storage to investigate the change of their muscle proteins. The degradation of total soluble, water soluble, high-salt soluble and low-salt soluble proteins was analyzed by SDS-PAGE. The high-salt soluble protein content declined from 84.99 mg · g^-1 to 49.47 mg · g^-1; water-soluble protein declined from 72.27 mg · g^-1 to 18.37 mg · g^-1; low salt soluble protein dropped from 11.15 mg · g^-1 to 3.39 mg · g^-1. In the three different structures of proteins, the decline of myofibrillar protein content is most obvious (decreased from 122.10 mg · g^-1 to 48.65 mg · g^-1, P < 0.05), and the content of myosinogen decreased from 37.79 mg · g^-1 to 26.57 mg · g^-1 (P < 0.05), while myostromin had no obvious change (P>0.05). The decrease of myosin heavy chain, actin, tropomyosin and some other protein bands in SDS-PAGE patterns indicates degradation of these proteins. Some new bands appeared at the last phase of storage.