| Collagen is one of the structural protein in animal tissues and the content of collagen is 25% in fish skin. With the development of China’s aquatic processing industry, a large amount of waste (50-60%) will be produced and the waste contains lots of collagen. Because conventional extraction collagen methods are usually time consuming, solvent consuming, energy dissipation and result in large amounts of collagen tissue residues, as well as the degradative collagen product. In this work, we firstly studied the effects of ultrasound on the separation crude protein of fish skin and the structure of fish skin collagen fiber. Then, we researched the ultrasound-aided method to extract the biologically active fish collagen, which was combined the ultrasonic pulse interval way and effects of extraction temperature, so as to establish a new and green ultrasonic extraction method. Otherwise, we established the three extraction equipment and contrasted their extraction effects, including the effects of structural and structural properties of collagen.1. There are about 3.55% crude protein in fish skin.The release of crude protein was maximum (37.37 mg/g) under the HIU2s oof 3s on tultrasonic pulse way, and the migrated amount of collagen was 0.63 mg/g. SEM showed, the loose of fish skin and the extension of collagen fiber were convenient for the subsequent collagen extraction. Meanwhile, the position of amide linkage in collagen fiber remained unchanged. Furthermore, the primary structure of subsequent collagen was intact.2. Ultrasound-aided extraction can significantly increase the extraction yield of collagen: after 30 min ultrasonic extraction, the yield of collagen was 28.32%,8.0% higher than that using conventional stirring method for 12 h. The yield of collagen increased with the increasing of ultrasonic pulse time. Ultrasound aided extraction can promote the solubility of collagen polymer chain (SDS-PAGE patterns showed) and the primary structure of collagen was intact.3. There existed differences in the solubility、viscosity and thermal stability of collagen under different ultrasonic pules ways while extracting:the solubility of collagen extracted by the pulse of HIU1s off 4s on was 10.43% higher than that the way of HIU4s off 1s on;the order of collagen viscosity under 4 ways of ultrasonic pulse were:HIU2s off 3s on>HIU1s off 4s on>HIU4s off 1s on;while the denatured temperature of collagen extracted by the pulse of HIU4s off 1s on was lower (33.5℃)than that the ways of others. UV, FTIR and CD spectra analysis showed that the helical structure of collagen remained intact except that collagen extracted under the ultrasonic pulse ofHIU 4s off 1s on.It indicated that, after extracted by the way of HIU4s off 1s on, part of triple helix in collagen were destroyed.4. Three extraction reactors:3 HIU combining with pump stirring treatments for 30 min ((P-H)30min)at 4,15, and 30℃,3 pump stirring treatments for 30 min (P30min) at 4,15, and 30 ℃, and continuous stirring for 12 h (S12h) at 4,15, and 30 ℃, were employed to extract fish skin and contrasted the effects on collagen properties. All treatment containing HIU ((P-H)30min) enhanced yield, solubility, and viscosity of collagen. With the extraction temperature increasing, the solubility and viscosity of collagen were increased. While DSC spectra indicated that, collagen extracted by the treatment of (P-H)30℃ 30mim gained decreased denatured temperature (33.5 ℃) and a less enthalpy (16.68 J/g).5. The functionality of collagen extracted under 3 different methods showed that, the oil absorption capacity of collagen extracted by the treatment of (P-H) decreased, but its emulsification and emulsion stability were better than that of others. While the gel performance of collagen extracted by the treatment of (P-H)30℃ 30min was relatively week.6. SDS-PAGE patterns showed there were no changes in primary structure of collagen. HIU combining with higher extraction temperature (30 ℃) induced the partial separation of the chains and the loss of the triple-helix conformation of collagen, and resulting in a lower denatured temperature and a less enthalpy. |
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