Comparison of the Physical and Chemical Properties of Collagens Extracted from Tortoise Shell using Three Methods
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Abstract:
The basic and mineral compositions of the ventral and dorsal shells of tortoise (Chinemys reevesii) were analyzed, and collagens (ASC, PSC, and H-PSG) were extracted from shell samples using acid, enzymatic, and hot-water assisted enzymatic methods. Subsequently, the physical and chemical properties of the extracted collagens were characterized through ultraviolet spectrometry, infrared spectrometry, SDS-PAGE, amino acid analysis, and scanning electron microscopy. The results indicated that tortoise shells had high protein (22.06%~22.50%), calcium (16 004.25~16 592.50 mg/100 g), and phosphorus (6 014.25~6 188.25 mg/100 g) contents. ASC, H-PSG, and PSC yields were 0.45%~0.51%, 4.38%~4.75%, and 1.47%~1.56%, respectively. The maximum absorption peaks of ASC, H-PSG, and PSC extracted from ventral and dorsal shell samples appeared at 220~226 nm. The infrared spectra and SDS-PAGE patterns showed that ASC and PSC were both type Ⅰ collagen with high purity and a relatively intact triple-helix structure, but H-PSG had degenerated into gelatin and had been partially hydrolyzed to collagen peptide. ASC, H-PSG, and PSC extracted from the ventral and dorsal shell samples had essentially the same amino acid composition, with abundant glycine (18.19%~24.10%) and proline (12.52%~15.05%). In terms of microstructure, ASC exhibited a superior three-dimensional network structure compared to H-PSG and PSC. In conclusion, the collagens extracted from the ventral and dorsal shells of tortoise using the same methods showed no significant difference in composition or properties; however, different extraction methods affected the yield, composition, and structure of collagens extracted from tortoise shells.