Extraction And Enzyme Modification Of Silver Carp Scale Gelatin And Physicochemical Stability Of Fish Oil-loaded Emulsion

Extraction of gelatin from by-products of aquatic processing,can effectively improve the utilization of the aquatic processing by-products but also can make up for the sold mammals commercial gelatin infectious diseases and religious problems of the defects.Because of its molecular structure with hydrophobic and hydrophilic regions,gelatin can be adsorbed to the oil-water interface to form and stabilize emulsion.Emulsions are widely used in various food systems,but they are thermodynamically unstable systems.Studying and improving the physicochemical stability of emulsions can expand their applications in food industry.In addition,as a nutrient delivery system,the analysis of digestion behavior of emulsion is also a research hotspot.In this paper,gelatin source,extraction method,enzymatic modification of gelatin on the molecular structure and physical and chemical stability of gelatin emulsion and in vitro digestion behavior analysis.The specific work is as follows:(1)The molecular weight distribution,structure,function and emulsification properties of silver carp gelatins extracted by three different methods were studied and discussed.The gelatins from silver carp scales were extracted by acetic acid method,hot water method and gastric protease method.SDS-PAGE,ATR-FTIR and AFM were used to characterize the gelatins from silver carp scales.Turbidity,WHC,FBC,EAI and ESI of silver carp gelatins extracted by three different methods were measured.Silver carp scale gelatin obtained by three different extraction methods was used to stabilize fish oil emulsion and characterized by digital camera and optical microscope.The results show that acetic acid-extracted gelatin(AAG),hot water-extracted gelatin(HWG),and pepsin enzyme-extracted gelatin(PEG)showed similar and four clear bands in sodium dodecyl sulfate-polyacrylamide gel electrophoresis pattern,whereas they showed different βchain amounts and β-sheet percentages.The water-holding capacity values(g water / g of gelatin)were: AAG(16.8 ± 1.1)> HWG(14.0 ± 0.7)≈ PEG(13.5 ± 1.6).The fatbinding capacity values(g oil / g of gelatin)were: AAG(11.8 ± 0.3)> HWG(9.5 ± 1.3)>PEG(5.3 ± 0.4).Emulsion droplet sizes and creaming index values decreased with the increase of gelatin concentrations for all the fish oil-loaded emulsions stabilized by three types of gelatins.Compared with PEG,AAG and HWG show similar and higher emulsion stability at high gelatin concentration(10 mg/m L).The analysis route of silver carp gelatin-stabilized emulsion is“extraction method-protein molecular weight distribution-protein molecular structure-molecular interaction-emulsibility-droplet structure-emulsion stability”route.(2)A transglutaminase(TG)modification method was developed to modify bovine bone gelatin(BBG),porcine skin gelatin(PSG),and cold-water fish skin gelatin(CFG)to change their physicochemical,functional,and emulsion stabilization properties.The results demonstrated that TG modification increased the molecular aggregation behaviors and change the physicochemical and functional properties of three types of gelatins.Further,TG-modified aquatic gelatin showed comparable foaming properties and higher emulsifying properties to mammalian gelatins,which suggested it could be potential mammalian gelatin replacer.Finally,TG-modified gelatins decreased the droplet sizes and increased creaming stability for fish oil-loaded emulsions.All these results suggested TG modification was an efficient method to improve the emulsifying properties of gelatins.Further,these results also showed significant differences among these three types of gelatins with and without TG modification.(3)To study the effects of antioxidant types on the stabilization and in vitro di gestion behaviors of silver carp scale gelatin-stabilized fish oil-loaded emulsions.Vita min C(VC)and vita min E(VE)had no obvious effects on the appearance,droplet size distribution,and droplet stability.In addition,both VC and VE could inhibit the phase separation of the emulsions at room temperature.VC slowed the liquid-gel transition of the emulsions at room temperature.The emulsion creaming stability decreased with the increase of VC concentrations,whereas increased with the increase of VE concentrations.Lipid oxidation of emulsion groups at room temperature were: VC < VE< Control < Pure oil.In addition,low temperature storage induced low lipid oxidation of the emulsions.Free fatty acids were mainly released from the silver carp scale gelatin-stabilized emulsions in the simulated intestinal fluid.Moreover,compared with the control group,VC could increase the FFA release percentages from the emulsions,whereas VE could decrease the FFA release percentages.All the results suggested that VC and VE had different effects on the stabilization and in vitro digestion behaviors of silver carp scale gelatin-stabilized fish oil-loaded emulsions.(4)The effects of gelatin type and antioxidant type on the stability and in vitro digestion behavior of curcumin-loaded fish oil emulsion were studied.Gelatin type and antioxidant type have different effects on droplet appearance,size distribution and stability.VC slowed down the liquid gel transition of the emulsion at room temperature.The oxidation of VC and VE emulsion lipids at room temperature is VC < VE< Control<Pure oil.In addition,low temperature storage can induce low fat oxidation of the emulsion.VC and VE can improve the retention rate of curcumin.In simulated intestinal fluid,the emulsion mainly released free fatty acids and curcumin.Compared with the control group,VC can increase the release rate of FFA in the emulsion,while VE can reduce the release rate of FFA in the emulsion.In addition,enzyme crosslinked gelatin showed excellent emulsion stability and curcumin protection properties.These results indicate that the type of gelatin and the type of antioxidant have different effects on the stability and in vitro digestion behavior of curcumin fish oil emulsion.In conclusion,the source and molecular structure of gelatin affect the stability of fish oil emulsion,and enzymatic modification can improve the stability of gelatin-borne fish oil emulsion.The addition of antioxidant can affect the physicochemical stability of emulsion.Different types of gelatin and different types of antioxidant have different effects on the protection of curcumin in emulsion system.This study deepened the research on the influence of “gelatin source-extraction method-molecular structurefunctional properties-emulsion droplet structure-emulsion stability”,and analyzed the possible influence of antioxidants in the emulsion system.It provides reference for emulsion stability study and nutrient digestion behavior.