Antioxidant Active Packaging Films Development Based On MCM-41 Mesoporous Silica Materials And Controlled Release Profiles Investigation

Fat oxidation influences both food quality and safety.With controllable and predictable release properties,these days,controlled released antioxidant active packaging has attracted wide attention among researchers instead of traditional antioxidant packaging.However,controlled release technologies now being applied in food packaging materials still have problems like material-selection limitation and limited slow release effect.Mesoporous silica materials have excellent properties such as high specific surface area and pore volume,adjustable pore size and modifiable surface,which give them bright prospects in the field of controlled release packaging.But as this stage,the release rate of active compound in controlled release packaging materials developed using mesoporous materials is not slow enough.Besides,the how the controlled release assemblies would influence the packaging and controlled release properties of active films are still not clear.In this work,antioxidant active packaging materials have been developed using MCM-41 mesoporous silica material as controlled release adsorbent,natural antioxidant α-tocopherol has been chosen as active compound,and low-density polyethylene has been adopted as film matrix.Factors including loading rate of α-tocopherol in α-tocopherol/MCM-41 assembly,addition amount of the assembly in polymer matrix,pore size and organic group of MCM-41 have been considered when developing active films.Packaging properties have been investigated from the aspects of morphology,crystallinity,mechanical and physical properties of active films.How these factors may influence the packaging properties of films and the mechanism have been investigated.Moreover,migration profiles of α-tocopherol from active films into fatty food simulant have been studied by migration tests,and molecular dynamics simulation has also been adopted to investigate controlled release mechanisms of MCM-41 on α-tocopherol.Main research contents and conclusions are as decribed below:(1)α-Tocopherol/MCM-41 assemblies and active films preparation and investigationOrthogonal tests have been designed to investigate the influence of processing conditions on loading amount of α-tocopherol in the assemblies.Properties of MCM-41 before and after loading have been investigated.Active films have been made by flat extrusion with LDPE resins incorporated with assemblies.The influence of active compound loading rate on release properties of active films has been studied,as well as the antioxidant properties of active films.Results showed that concentration of α-tocopherol in solvent was the main factor that may influence the loading rate,and α-tocopherol have been adsorbed successfully into mesoporous channels.Thermal stability property of α-tocopherol has been inproved through adsorption.Ordered structures of mesoporous silica materials have been maintained even after loading.As compared with directly α-tocopherol addition,the release of α-tocopherol in active film showed 62% decreased in diffusivity,and 57% prolonged release period.Antioxidant activity and slow release effect of active film both have been proven effective.(2)Infulence of additon amount of the assembly on properties of active filmsActive films have been prepared by incorporating with different amount of antioxidant assemblies.Packaging properties and release profiles of different films have been investigated.Loading amount have been found have influence on morpholy,crystallinity,tensile properties,transmittance and barrier properties of packaging films.On the one hand,as the addition amount increased,crystallinity and tensile strength decreased,transmittance,oxygen and water vapor permeabilities increased.On the other hand,mesoporous materials showed dual controlled release effect.Migration properties of active compound were not only influenced by pore channels of the adsorbent,but also slowed down as the migration path became more tortuose.(3)Infulence of pore size and organic group of adsorbent on properties of active filmActive films loading with different pore size and modified groups of MCM-41 have been prepared.MCM-41 before and after loading with α-tocopherol have been investigated thoroughly.Packaging properties and release profiles active films have also been studied.Results showed that MCM-41 with different pore size and organic groups have been synthesed successfully.α-Tocopherol has also been adsorbed onto the pore channels of the adsorbent.As to the films incorporated with different pore sizes of MCM-41,it has been found that the specific surface area of assemblies has prominent negative influence on crystallinity of films.And the tensile strength increased as the pore size of MCM-41 enlarged.The release rate of active compound increased as the pore size of MCM-41 increased on the whole.Modification with different organic groups inhenced the interactions between the assemblies and polymer matrix thus caused the packaging properties improved obviously.As the akly chain got longer,the release rate of α-tocopherol decreased.Amine group lead to the slowest release rate of α-tocopherol,as compared with directly addition,the diffusivity of α-tocopherol decreased 87%.(4)Molecular dynamics(MD)simulation study of α-tocopherol diffusionα-Tocopherol model and MCM-41 models with different pore size and surface groups have been build.MD simulation have been conducted to investigate the controlled release mechanisms of MCM-41 on α-tocopherol.Results showed that modification with organic groups changed the motion mode of α-tocopherol.As the pore size increased,the mobility of α-tocopherol increased.Diffuse of α-tocopherol in modified MCM-41 was influenced by both pore size and organic group.The essence of different controlled release effect could be attribute to interaction energy changes between the adsorbate and adsorbent.MD simulation results could be used to predict the migration profiles of α-tocopherol in active films.