Study On Preparation And Freshness Preservation Of Bamboo Cellulose Reinforced Composite Membranes

In order to solve the problems of current packaging materials that are difficult to degrade,often release toxic substances and exist environmental pollution,it has become an inevitable trend to develop a safe,green,non-toxic packaging material.Natural cellulose has the characteristics of biodegradability,high mechanical properties,high economic value and reproducibility,and is often used as a reinforcing material.Both chitosan and carboxymethyl cellulose have the characteristics of non-toxic edible,good biocompatibility,and are usually applied in the production of membrane materials.China's bamboo resources are abundant and the planting area is wide,but the utilization rate of bamboo processing residues is extremely low.Therefore,this project uses bamboo processing residues as raw materials to prepare nearly-nano-scale bamboo cellulose,and uses it as a reinforcement material to pass through solutions.Two composite reinforced packaging membranes were prepared by mixed casting with chitosan and carboxymethylcellulose.To investigate the effect of bamboo cellulose on the properties of the two membranes,to study its effect on preservation of cherry tomatoes,and to explore the application and value of this kind of environment-friendly composite packaging in the preservation of fresh fruits and vegetables.The main research contents and conclusions are as follows:(1)Bamboo fiber was prepared by the method of sulfuric acid hydrolysis combined with ultrasonic method using the remaining processed bamboo material as raw material.The response surface optimization method was used to analyze the three factors of sulfuric acid mass fraction,acid hydrolysis temperature and acid hydrolysis time for bamboo fiber production.The effect of the rate,and using a scanning electron microscope(SEM)and Fourier infrared spectrometer(FT-IR)on the characterization of bamboo cellulose.The analysis shows that the optimum preparation conditions of bamboo cellulose are:the mass fraction of sulfuric acid is 48%,the acidolysis temperature is 44?,and the time is 3.27h.Under the above conditions,the yield of bamboo cellulose was 56.07%.SEM analysis showed that the shape of bamboo cellulose was rod-shaped,with a diameter of about 500 nm,a length of about 500-600 ?m,a long major diameter,and a certain nanometer size.By FT-IR,it was found that the preparation of bamboo cellulose using the above method retained the characteristic functional group structure of cellulose.(2)Bamboo cellulose was used as a reinforcing material to prepare two kinds of composite membranes with chitosan solution and carboxymethyl cellulose solution by blending casting method.The appearance of the two membranes was compared and the physical properties(moisture permeability,light transmission,mechanical properties)were measured.Through analysis,the chitosan membrane was light yellow,the carboxymethyl cellulose membrane was colorless,and the surface roughness of the composite membrane increased with the increase of the content of bamboo cellulose.The addition of bamboo cellulose will significantly reduce the moisture permeability of the two composite membranes and reduce their light transmission.The mechanical properties test showed that the addition of bamboo cellulose will increase the mechanical properties of the chitosan membrane,which will reduce the elongation fracture rate of the carboxymethyl cellulose membrane,and increase the tensile strength and tensile modulus.Downward trend.(3)The preservative properties of the prepared membrane were studied.The effect of two composite enhancement membranes and a single chitosan,carboxymethylcellulose coating on physiological changes during storage over a period of 15 days was studied.The results showed that four kinds of coating treatments could reduce the weight loss rate of cherry tomatoes,delay the decrease of the hardness,and change the color of cherry fruits,and effectively inhibit the soluble solids,organic acids,reducing sugars and vitamin c in cherry tomatoes.The drop prolonged the storage time of the cherry tomatoes and achieved a good preservation effect.By comparison,the fresh-keeping performance of chitosan-bamboo cellulose composite enhanced cling membrane compared to that of two single solution coatings and carboxymethyl cellulose-bamboo cellulose composite reinforced membrane better.