Effect And Application Of Cellulose Nanocrystals Cooperated With Calcium Chloride On The Film-forming Properties Of Pea Protein Isolate

In recent years,with the increasing awareness of environmental protection and food safety,it is urgent to develop renewable and degradable biopolymer based food packaging materials.Pea protein isolate（PPI）has attracted wide attention in the field of food packaging because of its wide source,rich nutrition and good film formation.However,PPI-based films have some inherent shortcomings such as poor mechanical properties,low barrier ability,insufficient water resistance and strong water sensitivity,which greatly limit their application in the field of food packaging.Based on this,this study intends to prepare PPI-based films with cellulose nanocrystals（CNC）and Ca Cl₂ as reinforcers,investigate the effect of the synergistic effect of CNC and Ca Cl₂ on the functional characteristics of PPI-based films and the mechanism of action,and evaluate the preservation effect of different PPI-based films packaging on strawberry.In order to provide technical support for the development and practical application of new protein based gel membrane.The main research contents and results are as follows:1.Influence of CNC and Ca Cl₂ on the functional characteristics of PPI-based films:the simultaneous addition of 0.5%CNC and 4.5m M Ca Cl₂ had a synergistic effect on the tensile strength of PPI-based films;CNC or/and Ca Cl₂ improved the elongation at break and oxygen/water vapor barrier properties of the film,improved the transparency and surface color of the film,and enhanced the surface hydrophobicity and water resistance of the film,but had no significant effect on the film thickness and water content.The degradation rate of PPI-based film was more than 20%after 30 days of burial under natural conditions.2.Influence of CNC collaboration with Ca Cl₂ on physicochemical properties of PPI-based films:CNC or/and Ca Cl₂ made the cross section structure of the films more uniform,dense and ordered,but had no obvious effect on the surface structure;CNC and/or Ca Cl₂ improved the viscoelasticity of the film forming solution,induced the transition of free water to immovable water,improved the thermal stability of PPI-based films,and synergically enhanced the crystallization strength of the films at 20.17°.Fourier transform infrared（FTIR）results showed that hydrogen bond interaction existed between cellulose chains and protein molecules.3.The effect of CNC collaboration with Ca Cl₂ on the molecular properties of PPI-based films:CNC and/or Ca Cl₂ induced protein secondary conformation to shift fromα-helix toβ-folding;CNC molecules interacted with pea 7S（hydrogen bonds:Asn 229,Ser 216;Van der Waals force:Gly 96,Arg 95,Glu 94,etc.）and 11S(hydrogen bond:Gln 417,Thr 437,Arg 147,etc.;Van der Waals Force:Ala 379,Ser 148,Lys 357;C-h bond:Amino acid residues of Asn 378 globulin bind at specific sites,and the complex of CNC-Ca²⁺-11S globulin shown good binding stability.Hydrogen bond（CNC contribution）,disulfide bond(Ca²⁺contribution),ionic bond（co-contribution）and hydrophobic interaction（co-contribution）in the film forming system were important factors for synergistic improvement of film functional properties.4.Packaging application of PPI-based films:the weight loss rate,hardness,total soluble solids and color of strawberries packaged by PPI-based films had been improved to varying degrees,and the CNC/Ca Cl₂ composite film had effectively improved the storage quality of strawberries.