Sterilization Process Simulation And Optimization Of Aseptic Packaging Materials For Liquid Food Gable-top Carton

Aseptic carton packaging is one of the aseptic food packaging forms,with the advantages of easy forming,strong barrier,high mechanical strength,and good heat sealing.At present,the packaging structures that have been applied in engineering are mainly triangle,pillow,brick,diamond,and gable-top cartons.To further expand the application of gable-top cartons,the engineering community has tried to use gable-top cartons in the packaging of products with long shelf life and room temperature preservation in recent years.However,its complex carton structure molding makes the existing sterilization process unable to meet the product packaging requirements.Therefore,it is urgent to research the sterilization process of the pre-formed structure and packaging materials based on the gable-top carton aseptic filling machine.In this way,the safety and reliability of the sterilization process are guaranteed,and the basis and guarantee for the production of long-shelf-life packaging liquid products are provided.Based on the aseptic filling production process of the gable-top carton,the subject carries out the simulation and process optimization of the hydrogen peroxide（H₂O₂）aerosol and mixed steam sterilization process on the inner surface of the carton.Analyze the hydrodynamic mechanism of the sterilization process and obtain the optimized process parameters by simulations.At the same time,research and establish a microbial challenge test method,calculate and verify the sterilization efficiency of packaging materials,and further optimize the packaging material sterilization process of actual filling equipment.The main research contents and research results are as follows:（1）Simulation and process optimization of carton inner surface sterilization process based on H₂O₂ solution atomized aerosol.A numerical simulation method for the sterilization process of packaging materials was established based on the principle of air-assisted atomization aerosol.Firstly,the numerical model of air-assisted nozzle atomization was established.The Euler-Lagrange model was used to set the continuous phase and dispersed phase.And the droplet diameter distribution and spray shape under different atomization times and air pressure conditions were obtained.The dependability of the model was verified by comparing the atomization shape under actual conditions.Secondly,spray atomization sterilization process simulation was carried out to analyze the uniformity of aerosol coverage of sterilizer and compare the difference between different specifications of cartons.The results showed that 250m L carton had the problems of over-sterilization on the bottom surface and large residual solution covering,while 1000 m L carton had the matter of insufficient sterilization on the bottom surface and small solution contact area.Finally,the paper box sterilization process was optimized by adjusting the atomizing air pressure,atomizing air pressure,and atomizing parameters of the nozzle,which provided a basis for the sterilization parameter setting of the packaging material H₂O₂ aerosol of the gable-top carton filling machine.（2）Simulation and process optimization of carton inner surface sterilization process were based on H₂O₂ mixed steam.The compositional conditions of H₂O₂ mixed steam were analyzed by the relevant theory of fluid mechanics.The gas-liquid equilibrium diagram of the mixture with different components was obtained combined with the vapor pressure relationship of H₂O₂,water,and air mixture,and the phase transition temperature during the vaporization and condensation of H₂O₂ was analyzed.Carry out the simulation of the sterilization process of H₂O₂ mixed steam sprayed into gable-top cartons of different specifications to obtain the fluid motion law and motion speed,mass fraction of various components,and temperature in the carton.The experimental verification of the effectiveness of the simulation analysis was carried out.The actual sterilization efficiency of the packaging material was obtained after artificial inoculation of contaminated microorganisms on the packaging material surface,and the actual sterilization efficiency of the packaging material was obtained after sterilization under simulated conditions.The results showed that the simulation results were consistent with the actual results.Taking the 1000 m L roof box as an example,the influence of the H₂O₂ mixed steam temperature,outlet height,and outlet diameter on the sterilization efficiency was further analyzed,to provide a basis for optimizing its sterilization process.（3）Process optimization of sterilization was based on two test methods for sterilization efficiency of gable-top cartons.The effects of hydrogen peroxide solution concentration,vaporized hydrogen peroxide vapor temperature,vaporized hot air pressure,and UV time on sterilization efficiency were investigated experimentally.The response surface test was designed according to the Box-Behnken principle,the regression model of the sterilization efficiency of packaging materials was established,and the optimized parameters of the sterilization process were obtained and verified by experiments.The microbial challenge test method was used to determine the sterilization efficiency of packaging materials.Bacillus stearothermophilus spores were used as challenge test microorganisms to inoculate the inner surface of gable-top carton packaging materials quantitatively and evenly.The plate count method and the Most Probable Number（MPN）method were used to count the residual spores on the material surface after sterilization.And the sterilization efficiency was characterized by the Log Cycle Reduction（LCR）of inoculated spores.