(-)-Epigallocatechin gallate protected molecular structure of collagen fibers in sea cucumber Apostichopus japonicus body wall during thermal treatment

摘要

During thermal tenderization of sea cucumber body wall, protein oxidation always happens which disrupts its structural integrity. In this study, we investigated the effects of (-)-epigallocatechin gallate (EGCG, at 0, 5, 50, 125, 250 mu g/mL) to protect the structure of heated collagen fibers (CFs) in sea cucumber Apostichopus japonicus body wall. Many disintegrated collagen fibrils and fibril bundles were observed in samples with no EGCG by scanning electron microscope, while the integrity of CFs was protected in samples with 125 mu g/mL EGCG. Electron paramagnetic resonance results indicated heat-induced center dot OH in heated CFs were neutralized by EGCG, up to 83% in samples with 250 mu g/mL EGCG. Chemical analysis of the soluble fragments in heated CFs showed plenty of proteins and glycosaminoglycan were released in heated CFs, and the addition of EGCG into the samples reduced their dissolution. Analysis of differential scanning calorimetry and thermogravimetry indicated EGCG could enhanced the thermostability of CFs. Fourier transform infrared spectroscopy results showed EGCG at 125 mu g/mL prevented the conversion of alpha-helixes to beta-sheets, and affected N-H bending coupled with C-N stretching. In conclusion, EGCG could protect the structure of CFs in a dosage dependent way, and 125 mu g/mL was the most effective.