Effect of Cryoprotectants on Suppression of Protein Structure Deterioration Induced by Freeze-thaw Cycle in Pacific White Shrimp

This study aimed to elucidate the changes in Pacific white shrimp (Litopenaeus vannamei) myofibrillar protein as influenced by multiple freeze-thaw cycles as well as the stabilization effects of sucrose and trisodium citrate on shrimp myofibrils. Shrimp myofibrils in 0.1 M NaCl, 20 mM Tris-HCl (pH 7.5) were mixed individually with sucrose and citrate at concentrations of 0.05 M and were evaluated for Ca²⁺-ATPase activity, salt solubility, total and reactive sulfhydryl, and surface hydrophobicity during three freeze-thaw cycles. Sucrose and citrate had strong cryoprotective effects against freeze denaturation by retaining higher Ca²⁺-ATPase activity and salt-soluble myosin and actin, by slowing the reduction of reactive sulfhydryl (SH) and by exposing less hydrophobic groups at the surface of the protein compared with the no-additive sample. Results indicated that both cryoprotectants had suppressive effect against protein denaturation and helped stabilize white shrimp myofibrillar protein during the freeze-thaw process. This study suggests that sucrose and citrate stabilized the protein structure by retarding the unfolding of protein; thus, the native protein could be protected during frozen storage.