Studying on effects of boiling on texture, microstructure and physiochemical properties of sea cucumber body wall and its mechanism using second harmonic generation (SHG) microscopy

The structural foundation of texture changes in sea cucumber body wall (SCBW) during boiling was investigated using second harmonic generation (SHG) microscopy for the first time. The results from SHG signal imaging, light microscopy, scanning electron microscopy and transmission electron microscopy indicated the hierarchical structures of collagen in SCBW underwent progressive destruction with the prolongation of boiling time, including the depolymerization of collagen fibres, the uncoiling and disaggregation of collagen fibrils, the destruction of collagen microfibrils, the loosing of triple helix structure of collagen, and the degradation and gelatinization of collagen, which contributed to the progressive decline in texture indicators including shear force and hardness. SHG analysis also indicated that although collagen macromolecules such as collagen fibres, collagen fibrils and collagen microfibrils could be observed in 0.5 h-boiled and 2 h-boiled SCBW, monomeric collagen, the basic structural components of those macromolecules, has been already damaged.