Preparation And Properties Of Active Packaging Film With Antibacterial Nanofiber Particle Emulsify Pickering Emulsion

In the process of food storage and transportation,spoilage is the major factor causing food waste and food quality reduction.Reducing food spoilage and ensuring food quality and safety have become a major and urgent task.Active packaging prevents food spoilage by releasing functional ingredients such as antibacterial or antioxidant,thus maintaining or improving the quality and safety of food.Under the background of green packaging,it is great practical significance to develop multi-functional active packaging materials,based on green technology,by utilizing biomass materials and natural antibacterial agents.In this study,oil-in-water Pickering emulsion was stabilized by using surface-carboxylated cellulose nanocrystal（TOCNC）grafted with polyethyleneimine（PEI）as solid particle（TOCNC-PEI）and oregano essential oil as oil phase.Subsequently,Pickering emulsion was added to cellulose nanofibril（CNF）suspension as film matrix,and then the bio-based active packaging film with antibacterial and antioxidant properties was prepared by casting.The research contents and results were as follows:（1）Preparation and properties of TOCNC-PEI antibacterial nanofiber particle:surface-carboxylated cellulose nanocrystal（TOCNC）was obtained by oxidization of microcrystalline cellulose（MCC）with TEMPO and subsequent homogenization,with the degree of oxidation（DO）of 0.24 mol/mol and particle size of 98.3±1.64 nm.TOCNC-PEI₈₀₀,TOCNC-PEI₁₈₀₀ and TOCNC-PEI₂₅₀₀₀were prepared by grafting PEI with different molecular weight to TOCNC,and all particles have an obvious antibacterial effect against L.monocytogens and E.coli.With the increase of the molecular weight of PEI,the particle size was gradually decreased;the Zeta potential was gradually increased.TOCNC-PEI₂₅₀₀₀ has a smaller particle size,the highest of Zeta potential and the most stability of suspensions system compared TOCNC-PEI₈₀₀and TOCNC-PEI₁₈₀₀,no flocculation was produced in the suspensions,and the minimum inhibitory concentration（MIC）against L.monocytogens and E.coli were 0.50 mg/m L.（2）Pickering emulsion with antibacterial properties was stabilized by TOCNC-PEI:The preparation of oil-in-water Pickering emulsion,TOCNC-PEI₂₅₀₀₀ was used as the particle and oregano essential oil was used as the oil phase.The stability,morphology,antioxidation and antibacterial properties of the Pickering emulsion with the oil-water mass ratio from 1:9 to5:5 and the concentration of particle at 1.1-1.4 wt%were studied.When the concentration of particle at 1.3 wt%and the oil-water mass ratio was 4:6 and 5:5,the droplet size was smaller,the encapsulation rate was higher,the emulsion system was more stable,DPPH free radical scavenging rate of the emulsion with the oil-water mass ratio of 5:5 reached 79.96±0.09%,and the MIC against L.monocytogens and E.coli were 1.56μL/m Land 1μL/m L,respectively.When the oil-water mass ratio was 4:6 and the particle concentration was 1.3 wt%and1.4 wt%,the droplet size was smaller and the encapsulation rate was higher.With increasing the concentration of TOCNC-PEI₂₅₀₀₀,the antioxidation and antibacterial of Pickering emulsion remained almost unchanged.（3）Preparation and properties of active packaging film based Pickering emulsion:Bio-based active packaging films were prepared by adding antibacterial and antioxidant Pickering emulsion to CNF suspensions and then casting.With the increase of oil phase proportional in emulsion,the barrier property of packaging film to water vapor and light,as well as the antioxidation and antibacterial properties were gradually improved.In addition,the film with an oil-water mass ratio of 5:5,the barrier performance of water vapor and light was best,while its mechanical property,thermal stability and oxygen barrier property were slightly lower,but the DPPH free radical clearance rate was 33.34±0.17%,the inhibition rate against L.monocytogens reached 92.48±0.87%,showed good antioxidant and antibacterial properties.