Modification Of Whey Protein-polysaccharide Films By Two-stage Heating And Its Application

In the face of resource exhaustion,environmental pollution and other problems,we are forced to look for pollution-free,recyclable,sustainable and degradable materials to replace traditional packaging materials.The original intention of this experiment is to explore the replacement of plastic products with protein-polysaccharide based films in order to reduce environmental pollution and provide the basis for green development.It has to be admitted that there is still a long way to go.Although natural macromolecule whey isolated protein,Pullulan polysaccharide,can form film independently,it has defects in mechanical properties and barrier properties,which hinder the application and development of edible film to a certain extent.The film prepared in this experiment is a composite film composed of pullulan polysaccharide,whey protein isolate and sodium caseinate,which can complement the shortcomings of independent substrate film.On the basis of previous studies,this experiment expands and explores in depth.In the experiment,the film substrate is dechained at low temperature at 35,40,45,50,55℃ in one section and irreversibly denatured at 85℃ in the second section to improve the film preparation process.The mechanical properties and barrier properties of the films were compared,and the mechanism of hydrophobicity and color change was analyzed.The experimental results show that the oxygen resistance and mechanical properties of the films modified by two sections of heated crosslinking are improved compared with those of unmodified crosslinking and one section of heated crosslinking,and the uniformity of the films is enhanced by infrared spectroscopy and scanning electron microscopy.In summary,the film heated at 45-85℃ has the highest physicochemical and mechanical properties.In the middle stage of the experiment,on the basis of two stages of heating in the early stage of the experiment,it was found that the denatured film at 45-85℃ had good barrier properties and mechanical properties.Based on this,the edible film under these conditions was compounded with kraft paper.After drying,the paper-based protein-polysaccharide film was modified by Maillard.The purpose of this experiment is to prepare high barrier and high strength composite membrane by impregnating the mixture solution of whey protein isolate,sodium caseinate and Pululan polysaccharide with kraft paper.Maillard reaction(MR)was used to further optimize the film forming properties.In this experiment,three kinds of films were prepared,which were the composite of undenatured protein solution with paper base,the composite of denatured protein solution with paper base,and the composite of denatured protein solution with paper base after Maillard high temperature treatment.The mechanical properties,barrier properties,color and water resistance s of the films was measured.The experimental results show that the elongation at break is the highest when the film is heated in two stages(45-85℃)and subjected to Maillard reaction.The highest tensile strength,the best oxygen barrier;Hygroscopicity enhanced,water vapor barrier performance enhanced;the surface hydrophobicity of the film is enhanced,and the oil phobicity is reduced.In the third stage of the experiment,two heated films were loaded with blueberry anthocyanin with antioxidant activity to prepare active films to explore the effect of blueberry anthocyanin on the properties of the films.Based on the excellent antioxidant properties of blueberry anthocyanin(BA),active films were constructed with whey protein isolate(WPI),Pullulan polysaccharide(PUL)and sodium caseinate(SC)as the carrier by casting method.The effects of BA addition on mechanical properties,barrier properties and surface microstructure of the composite films were analyzed.The experimental data show that when the additive amount is 0.9%,the film has the maximum elongation at break and tensile strength,the best oxygen blocking property,the water vapor blocking property,and the highest DPPH free radical scavenging rate of the film is 87%.Infrared spectroscopy and scanning electron microscopy analysis showed that BA had good compatibility with the substrate and significantly improved the roughness of the surface of the film.The active film containing 0.9% BA could effectively improve the oxidation and spoilage rate of beef,which had a good application prospect.