Study On Nanocellulose/Starch Active Packaging Film Based On Tea Polyphenol-Chitosan Nano-Sustained Release System

Foods deterioration may occur during storage and transportation due to some unfavorable factors such as microorganisms and oxygen,which causing the waste of resources and even endangering human health.Traditional packaging is limited in their ability to extend the shelf life of food and control “White pollution”.Therefore,a new packaging form called active packaging has been proposed to extend the shelf life of foods by releasing antibacterial agents or antioxidants while maintaining the quality of the food.In this study,a kind of composite bioactive packaging film with long-lasting antimicrobial and antioxidant properties was prepared by using starch as film-forming substrate,nanocellulose as a reinforcing agent,and tea polyphenols loaded chitosan nanoparticles as antibacterial agent and antioxidant,which satisfied the packaging requirements in transparency and strength at the same time.Firstly,the nanocellulose was separated from the three kinds of non-wood fibers(bamboo,cotton linters and sisal)by TEMPO oxidation combined with high pressure homogenization,and the three kinds of nanocellulose were further mixed with starch in different proportions to form a film.The effects of raw material and addition amounts on the properties of the starch film were compared.The study found that the three kinds of nanocellulose had similar morphology and structure,but different sizes and crystallinity.The addition of nanocellulose increased the mechanical and barrier properties of the starch film,but reduced elongation at break and thermal stability.Among them,4 wt% of bamboo nanocellulose had the best reinforcing effect on starch.The tea polyphenols loaded chitosan nanoparticles were prepared by ionotropic gelation method.The effects of chitosan and sodium tripolyphosphate ratio,tea polyphenol concentration and chitosan solution pH on the encapsulation efficiency,drug loading capacity,zeta potential,particle size and polydispersity coefficient(PDI)of nanoparticles were investigated.The results showed that the best utilization of tea polyphenols could be achieved with a weight ratio of 2:1(CS:TPP)at pH 4.0 and a tea polyphenols concentration of 0.01 g/ml.At this time,more uniform and stable nanoparticles with a diameter of about 200 nm could be obtained.The release behavior of the nanoparticles demonstrated that the nanocarrier could delay the release rate and increase the release cycle of tea polyphenols.Finally,a composite active film used for food packaging was prepared by impregnating the optimized nanocellulose/starch membrane into tea polyphenols loaded chitosan nanoparticle solution.Tests show that the tensile strength and transparency of the composite film with the addition of tea polyphenol-chitosan nanoparticles were greatly improved,and the elongation at break was significantly reduced.The active composite film showed good oxidation resistance in the antioxidant test and some antibacterial effects against Escherichia coli in the antibacterial experiment.