Optimization of Preparation Process of Polypeptide Metal Chelates from the Scales of American red fish (Sciaenops ocellatus)

In this paper, the preparation of polypeptides and the synthesis of polypeptide metal chelates from American red fish（Sciaenops ocellatus ）scales were studied and optimized. Polypeptides were prepared from the scales of American red fish. The molecular weight of the peptides was analyzed by gel chromatography. Polypeptide metal chelates were synthesized by water system method and the metal chelating rate was determined by EDTA complexometric titration method. L₉(3⁴) orthogonal test was used to optimize the processing conditions of polypeptide metal chelates. The binding of polypeptide to metal was verified by detecting polypeptide and metal chelate by infrared spectroscopy. The molecular weight of polypeptide was about 1~6 kDa by gel chromatography analysis. The preparation conditions of polypeptide zinc chelate were obtained by orthogonal experiment, that is, the mass ratio of zinc chelate was 2:1, pH5.5, temperature 55℃, time 60 min. The optimal chelating conditions were mass ratio 2:1, pH6.0, temperature 35℃ and time 55 min. Under the optimized condition, the chelate ratio of zinc and copper were 78.21% and 91.24% respectively. The infrared absorption spectra showed that Zn²⁺, Cu²⁺ and -NH₂ were successfully combined. The results showed that the chelation rate was significantly improved under the condition of this process, and it was rich in metal ions, low cost and promising market prospect, which would be conducive to the high-value application of marine fishery processing by-products and promote the technological upgrading of fishery processing industry.