Study On Preparation Of Channel Catfish Skin Gelatin And Functional Properties

Fish skin is a main by-product of fish processing, which contains large amount of collagen and can be produced good quality gelatin to enhance the value. This dissertation focused on using Channel Catfish skin to produce gelatin, which not only reduces environment pollution but also enlarges the raw material of gelatin and develops a new foodstuff.The gelatin processing from Channel Catfish skin was studied. The fish skin was treatmented using sodium hydroxide and sulfuric acid, and then was prepared with hot water extraction. The main dependent variable was gel strength,viscosity and yield, the optimal processing conditions were as follows: sodium hydroxide 0.3% (w/v), sulfuric acid 0.4% (w/v), treatment time 120 min, extracting temperature 45℃and time 6h. Under these conditions,the obtaining gelatin were 672.2g gel strength, 9.46 mPa·S viscosity and 65.21% yield respectively.In order to removing the fishy flavor Channel Catfish skin gelatin, the removing methods have been studied. The flavor components of Channel Catfish skin gelatin was analysed by headspace solid phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS).The removing fishy flavor with active carbon,β-cyclodextrin and yeast was compared. The results showed that the flavor components of channel Catfish skin gelatin were mainly aldehydes and ketones. The four components of Hexanal, Heptanal, 2,4-heptadienal and 2,6-nonadienal may contribute most to the fishy flavor. The three methods of active carbon,β-cyclodextrin and yeast all can remove the fishy flavor. But the active carbon was the best one,the fishy flavor was removed.The amino acid composition and structure of Channel Catfish skin gelatin were studied.In fish skin gelatin, there were large amount of glycine,alanine,proline and hydroproline. SDS-PAGE electrophoresis and intrinsic viscosity determination showed that the molecular weight distribution of fish skin gelatin was more centralized than pig gelatin.The average visco-molecular weight of fish skin gelatin was 78,996,Surface hydrophobicity( S 0) was 2.985 and the pI was about 8. Channel Catfish skin gelatin was consisted of tri-helix and single-helix configuration by FT-IR and X-ray analysis.Filming properties of Channel Catfish skin gelatin was studied.A transparent and bright film was formed with 6% gelatin and 1/6 glycerol,which had good mechanical properties, oxygen barrier properties and low vapor barrier properties. Fish skin gelatin and pullulan were blended to make film,and the properties of their blended film depended on the gelatin ratio in blends.When the ratio of gelatin to pullulan was 3:1,the oxygen barrier property of the blend film increased.