Changes in the myosin secondary structure and shrimp surimi gel strength induced by dense phase carbon dioxide.

Dense phase carbon dioxide (DPCD) could induce protein conformation changes. Myosin and shrimp surimi from Litopenaeus vannamei were treated with DPCD at 5-25MPa and 40-60°C for 20min. Myosin secondary structure was investigated by circular dichroism and shrimp surimi gel strength was determined using textural analysis to develop correlations between them. DPCD had a greater effect on secondary structure and gel strength than heating. With increasing pressure and temperature, the α-helix content of DPCD-treated myosin decreased, while the β-sheet, β-turn and random coil contents increased, and the shrimp surimi gel strength increased. The α-helix content was negatively correlated with gel strength, while the β-sheet, β-turn and random coil contents were positively correlated with gel strength. Therefore, when DPCD induced myosin to form a gel, the α-helix of myosin was unfolded and gradually converted to a β-sheet. Such transformations led to protein-protein interactions and cross-linking, which formed a three-dimensional network to enhance the gel strength.