Preparation And Properties Of Hypocrellin /CNF/PLA Antibacterial Packaging Film

With the improvement of people's life quality,the freshness and safety of food have attracted the attention of consumers.Food is easy to spoil during storage and transportation,which leads to a series of foodborne diseases.Antibacterial packaging materials were developed to keep the quality and safety of foods by inhibiting the growth of pathogenic bacteria.Therefore,the development of antimicrobial packaging film by using natural antimicrobial agents and biomass materials can inhibit the growth of food pathogens extend the shelf life of food,ensure food safety,and protect the natural environment.Nano-cellulose film has excellent mechanical properties and barrier property.The mechanical properties,barrier properties and antibacterial properties of PLA film can be improved by coating CNF layer with natural antibacterial agent hypocrellin on the surface of PLA film.In this paper,CNF/PLA antibacterial packaging film was prepared by coating hypocrellin loaded CNF on the surface of PLA film with excellent antibacterial and barrier properties.It provides theoretical and practical reference for the application of biomass-based degradable materials in food.The following is the main content and results of this study:(1)The effects of different p H(p H=2,p H=7,p H=12),light(fluorescence,UV light,dark),oxygen concentration(oxygen,nitrogen,air),and temperature(4?,25?,38?)on the retention rate and antibacterial properties of hypocrellin solution were studied.The chemical structure of hypocrellin was relatively stable under the acid and neutral conditions.The light,temperature,and oxygen concentration had a little effect on the retention rate of hydpocrellin.Hypocrellin has a good antibacterial activity,and the minimum inhibitory concentration is 4?g/m L against Listeria.M.Light reduced the antibacterial property of hypocrellin solution,but temperature and oxygen had a little effect on the antimicrobial property of hydpocrellin.(2)The adsorption effect of CNF to hypocrellin was studied by the static experiment.The results showed that hypocrellin can be effectively adsorbed on the surface of CNF.The adsorption equilibrium was reached after 120 min,and the adsorption capacity was 2.47±0.12 mg/g.This CNF-loaded with hypocrellin was used to prepare HA/CNF antibacterial film.The effect of different hypocrellin content on the mechanical properties,barrier properties and antibacterial properties of HA/CNF film were studied.The results showed that the bacteriostatic rate of the film filmagainst Listeria.M was 95%,when the content of hypocrellin reached 0.3%(w/w).Considering the mechanical properties and cost,the best dosage of hypocrellin was 0.3%(w/w)and the inhibition rate of the resulting film was more than 90%.The inhibition rate of HA/CNF film was higher than 85%after 28 days storage at 25?in light.(3)Low temperature Plasma-treatment improved hydrophilicity of PLA and the adhesion strength between PLA and CNF during the preparation of CNF/PLA film.The optimum conditions were defined as plasma treatment time of 40 s,discharge voltage of 125 V,and electrode distance of 4.5 cm.The contact angle of the PLA film was 42.4°,and the peel strength between the PLA film and CNF was 39.5 N/m at the optimum condition.When CNF was coated on the PLA film with a thickness of 19.5?m,the prepared CNF/PLA film exhibited good mechanical and barrier performance,with the tensile strength of89.40 MPa,the elongation of 4.8%,the modulus of elasticity of 3357 MPa,the oxygen transmission of 160 cc/m~2·d,the transmittance of 43.21%,and the water vapor transmission of 90.3 g/m~2·d at 38?,RH 90%.(4)Cheese was vacuum-packed with PE,PLA and CNF/PLA films,respectively.The Cheese samples were stored at 4?for 21 days and then went for quality testing such as total bacterial count,Thiobarbituric acid reactive substances(TBARS),Peroxide value(POV),carbonyl content,chroma,and texture.The results showed that the total bacterial count of cheese packed in PE film group and PLA film group was more than 7.00 log CFU/g,and CNF/PLA film group was less than 4.00 log CFU/g after 21 days storage at 4?.CNF/PLA antibacterial film can inhibit the growth of Listeria.M on the cheese,delay the oxidation of protein and fat,and slow the change of color and texture of cheese.