Preparation And Application Of N-Succinyl Chitosan Immobilized Nisin And Perilla Frutescens Essential Oil

In this paper,nisin-N-succinyl chitosan bacteriostatic agent(NNSC)was prepared by immobilizing nisin(Nisin)and perilla essential oil(PEO)onto N-succinyl chitosan(NSC).And perilla essential oil-nisin-N-succinyl chitosan bacteriostatic agent(PEO-NNSC).NSC,NNSC and PEO-NNSC were characterized by FT-IR,XRD and TG,and their antibacterial and toxicological properties were explored.The process of PEO-NNSC was carried out by homogenizing method instead of ordinary stirring in the dispersion solution system.The N-succinyl chitosan-based composite film was prepared by flow method.The microstructure,mechanical properties,water vapor barrier properties,optical properties and preservation performance of strawberry,white fungus and stalk mushroom were studied.The specific research contents are as follows:(1)Preparation of bacteriostatic agents NNSC and PEO-NNSC.FT-IR analysis showed that the chitosan had an N-acylation reaction,and nisin changed the structure of N-succinyl chitosan,and a hydrogen bond was formed between the perilla oil and NNSC.XRD analysis showed that the N-acylation reaction of chitosan made the molecular arrangement more disordered,the crystallinity decreased,and the water solubility increased.The addition of nisin and perilla essential oil to N-succinyl chitosan continued to decrease the crystallinity.The thermogravimetric analysis(TG)of NSC,NNSC and PEO-NNSC showed that PEO-NNSC had the lowest thermal stability.The results of bacteriostatic experiments showed that PEO-NNSC had the best antibacterial effect against Staphylococcus aureus,Escherichia coli and Salmonella.Cytotoxicity experiments confirmed that NSC,NNSC and PEO-NNSC are non-toxic and harmless,and can be used in food preservation.(2)The PEO-NNSC was optimized by homogenization process,and the products of NSC,NNSC and X-NNSC(using N-succinyl chitosan as carrier to immobilize nisin and perilla essential oil)were prepared by the flow method.It is a composite film of perilla essential oil concentration %,X = 0.5,1,1.5,v/v).It was found that nisin and perilla oil can improve the mechanical properties,water vapor barrier properties and optical properties of the film.FT-IR analysis shows new interactions in the composite.SEM analysis showed that perilla essential oil increased the roughness of the biocomposite film,indicating that PEO has good dispersion in the NSC matrix.X-ray diffraction measurements showed that the addition of Nisin and PEO decreased the crystallinity of the film.In addition,the composite membrane with Nisin and PEO added has good antioxidant activity against S.aureus,E.coli,S.entertidis and P.tolaasii has good antibacterial activity,and the optimized antibacterial effect of PEO-NNSC is significantly increased.(3)Antibacterial and fresh-keeping experiments were carried out on strawberry,white fungus and slider mushroom by NSC,NNSC and 1.5-NNSC coating liquid.The results show that the 1.5-NNSC coating can maintain the color and hardness of strawberry,reduce the weight loss rate,prevent the rapid decay of strawberry,and also inhibit the microbial growth of Tremella fuciformis and S.chinensis.In short,biocomposites with Nisin and PEO have good prospects for food preservation as biodegradable and environmentally friendly packaging materials.