Preparation Of Octenyl Succinate Cassava Starch Ester Antibacterial Film And Its Application In Sweet Cherry Preservation

At present,most of the films used in the market are made of petroleum-based compounds.Petroleum-based packaging films were easy to cause a lot of pollution,and they were still non-renewable.At present,the search for environmentally safe and renewable packaging film has become a hot issue.Cassava starch,as an environmentally friendly and abundant substance,makes it an excellent choice to replace petroleum-based films.In this paper,the research and development of cassava starch products were deeply developed to realize the high-value utilization of cassava,which opened up a new application for new bio-based packaging film and provided a theoretical reference in the field of food preservation.In this study,tapioca octenyl succinate was used as raw material,and the properties of the blended film of tapioca octenyl succinate（OSCS）/chitosan（CS）/nano-ZnO were optimized by response surface methodology.Then,the blended film andε-polylysine（ε-PL）were made into an antibacterial film of tapioca octenyl succinate.The particle size potential change of the film-forming solution and the mechanical,barrier,optical and color aspects of the antibacterial film were studied,and scanning electron microscopy and Fourier infrared spectroscopy were used.Finally,the antibacterial effect and cytotoxicity of the antibacterial film were evaluated,and it was initially applied to cherry preservation to explore the preservation effect.The main results and conclusions of this study are as follows:Through the single factor response surface,it was determined that the optimum preparation process of octenyl succinic cassava starch ester/chitosan/nano-ZnO blended film was as follows:the mass ratio of octenyl succinic starch ester to chitosan was 1:1（m/m,m being the dry mass of starch and chitosan）,the addition of nano-ZnO was 1.9%（m/M,m being the dry mass of starch and chitosan）,and the addition of glycerol was 49%（m/M,m being the dry mass of starch and chitosan）,the comprehensive score of performance optimization of the blended film is 0.6033.The octenyl succinic acid tapioca starch ester antibacterial film solution was detected by a laser particle size analyzer,and it was found that the film-forming components formed a compound through electrostatic and covalent interaction at the film solution stage,with excellent stability.The antibacterial film was found to have good mechanical properties using a universal electronic testing machine,the surface hydrophobicity of the film was found to be improved using an interface tensiometer,and the swelling rate was tested to have excellent deformation resistance,the film tested by ultraviolet spectrophotometer had ultraviolet blocking effect.FT-IR and fluorescence microscope showed that the antibacterial film of octenyl succinate cassava starch ester was formed by hydrogen bonding and Schiff base reaction.After the film was formed,the diffraction peaks of octenyl succinate cassava starch ester at2θ=15°,17°,18°and 23.5°and chitosan at 2θ=9°,11°,14°,17°and 21°disappeared,indicating that the four materials were well mixed.Scanning electron microscope showed that the structural density of octenyl succinic cassava starch ester antibacterial film increased with the increase ofε-PL content.Thermogravimetric analysis showed that the addition ofε-PL improved the thermal stability of the composite film to some extent.The final weight loss rate of octenyl succinic cassava starch ester antibacterial film was lower than that of the whole starch film,and the weight loss rate of the whole starch film was 82.87%,and the weight loss rate of the octenyl succinic cassava starch ester antibacterial film were about72%.The structure of the octenyl succinic cassava starch ester antibacterial film had higher thermal stability.The antibacterial effect of octenyl succinic cassava starch ester antibacterial film was comprehensively evaluated by bacteriostatic circle and bacteriostatic rate.It was found that whenε-PL was 8%,it had excellent antibacterial performance.At the same time,it was observed by scanning electron microscope that OSCS/CS/ZnO/8%ε-PL film would cause bacteria to deform,collapse,cells fester,the surface became rough,bacteria reunited with each other,and the cell membrane was no longer complete.OSCS/CS/ZnO/8%ε-PL film with the best bacteriostatic effect was screened for cytotoxicity and sweet cherry preservation experiments.The experimental results showed that OSCS/CS/ZnO/8%ε-PL film had good cell compatibility and preservation effect.When used for cherry preservation,OSCS/CS/ZnO/8%ε-PL film effectively reduced cherry rot,stem dryness and weight loss,and kept the surface.By the eighth day of cherry storage,the rot rate of CK group and PE group reached 86.7%and 93.3%respectively,while the rot rate of OSCS/CS/ZnO/8%ε-PL film group was only 40%.On the 8th day,the drying index and weight loss rate of cherry stalks in CK group reached 286.7%and 36.0%respectively,while those in OSCS/CS/ZnO/8%ε-PL film group were only 233.3%and 24.4%respectively.It can also maintained the surface color of cherry,increase the soluble solid content to 17.8*Brix,and preserve the anthocyanin content.The anthocyanin content of OSCS/CS/ZnO/8%ε-PL film is 7.03(OD₅₃₀-OD₆₀₀)g^-1 FW at 8 days,which is the highest in the same period.The decomposition of flavonoids was inhibited,and the highest flavonoid content in OSCS/CS/ZnO/8%ε-PL film reached 16.73 OD₃₂₅·g^-1·FW at 6 days.Compared with other groups,the treatment with OSCS/CS/ZnO/8%ε-PL membrane had lower MDA content,and there was a significant difference（P<0.01）.