| In recent years,the researches on emulsions has been received more and more attention.Especially,Pickering emulsions and high internal phase emulsions(HIPEs)have been widely used in various fields such as food,medicine,cosmetics,and so on.At the same time,the choice and applications of emulsifiers have also received widespread attention.Emulsifiers are preferred to safe,biodegradable,renewable,and widely sourced bio-sourced particles,including polysaccharides,proteins,and lipids.In this paper,the collagen fiber extracted from cowhide was used as an emulsifier and mixed with algae oil,and then the Pickering emulsion was prepared by ultrasonication.Then,the volume fraction of the internal phase was increased by high-speed centrifugation and glutamine transaminase(TGase)cross-linking to increase the range of applications of the emulsions.In the study,Pickering emulsion was prepared with acid-soluble collagen fiber extracted from bovine hides as an emulsifier.The factors determining the stability of emulsion were investigated,such as collagen fibers concentration(0.01-1.5 wt%),salt ion concentration(0.1-1.0 wt%)and pH(2.0-10.0).The results showed that the length of the collagen fibers was 600-900 nm and its isoelectric point was 7.5.The emulsion was stabilized by 0.1 wt%collagen fibers.In morphology,the particle size of the emulsion was gradually reduced with the rise of the collagen fibers concentration.Besides,the droplets of 0.3 wt%collagen fibers emulsion remained evenly distributed after centrifugation.The stability of the emulsion gradually improved as the increase of the collagen fibers concentration.The results of rheological analysis displayed that the emulsion was in a gel-like state,and the elastic modulus(G’),the viscous modulus(G")and the yield stress were enhanced as the increased concentration of collagen fibers.What’s more,the acidic condition was favorable for the emulsion to keep stability and the addition of salt ions enlarged the particle size of the emulsion.The medium-high internal phase emulsions were prepared by centrifugation at 10,000 g for 15 min and then,the effect on the emulsion was investigated after heating at 90℃ for 40 min.The results showed that the medium-high internal phase emulsion of a certain concentration of collagen fiber(≥0.3 wt%)had a better gel-like morphology as well as stronger stability,and kept homogeneous after centrifugation.The viscoelasticity,the yield stress and the volume fraction of the internal phase enhanced,meanwhile the latter grow up to 60%compared with the Pickering emulsion.High internal phase emulsions(HIPEs)with the internal phase volume fraction of 72%were prepared by adding different dosage of transglutaminase(TGase).The dosage of TGase was 5,10,20,30,40 U/g collagen fibers,and HIPEs was investigated after heat treatment at 90℃ for 40 min.Microscopy results exhibited that the unheated particle size of HIPEs droplets reduced significantly with the rise dosage of TGase and the particle size had not change when the TGase reached to 20 U/g collagen fibers.The particle size of emulsion was increased after heating.As the dosage of TGase more than 30 U/g collagen fiber,the particle size of heated HIPEs was almost the same as the unheated.HIPEs also exhibited a gel-like state after TGase treatment.In addition,their viscoelasticity and yield stress were better than MIPEs,and HIPEs and MIPEs maintained uniform states during storage for 14 d.In summary,collagen fibers can be used as a novel food-based emulsifier,and the Pickering emulsion and(medium)high internal phase emulsion prepared by it have broad the application prospects in food,especially as a potential fat substitute... |
PDF Full Text Request