Preparation Of Nano-selenium Composite Packaging Material And Its Application In Fruit And Vegetable Preservation

Nano-selenium has the advantages of low toxicity and high bioactivity.Currently,nano-selenium has been widely used in the fields of animal production,biological medicine and plant nutrition,but there are few studies on the application of nano-selenium in food packaging materials.This study used anoxygenic phototrophic bacteria(Rhodobacter sphaeroides YL75)as materials to explore the optimal parameters for preparing biological nano-selenium by microbial synthesis method.In view of the physiological and pharmacological effects of bio-derived nano-selenium,this study applied bio-derived nano-selenium to food packaging materials,and explored the optimal parameters for preparing plastic film food packaging materials with nano-selenium and the migration and change rules of selenium in packaging materials.The application effect of nano-selenium composite packaging material in litchi,F.velutipes,tomatoes and pickled radish was explored.The main results were as follows:1.Study on preparation of nano-selenium by microbial synthesis:Taking the conversion rate of selenium as an index,four factors were emphatically optimized,and the order of influence degree was initial pH of culture medium,culture time,Na2SeO3 addition,inoculation amount.The optimum parameters of these four factors were 2.5 mmol/L Na2SeO3,5 days culture time,initial pH 7.0 and 15%inoculum size,respectively.The selenium conversion rate was 93.02%.The nano-selenium particles were spherical or nearly spherical with an average diameter of about 100 nm.2.Preparation and properties of nano-selenium composite packaging material:The response surface methodology was used to optimize the addition of nano-selenium,nano-titanium dioxide and attapulgite,and the optimal addition of nano-powder masterbatch was determined to be nano-selenium 9.69%,nano-titanium dioxide 11.93%and attapulgite 8.18%.Oxygen permeability of nano-selenium composite packaging material prepared by by adding the masterbatch to polyethylene plastic particles(mass ratio:3:77)was lower than that of common packaging material(pure polyethylene plastic film)(p<0.05),longitudinal tensile strength was higher than that of common packaging material(p<0.05),and the antibacterial performance against Escherichia coli and Staphylococcus aureus was better than that of common packaging material(p<0.05).3.Study on migration behavior of nano-Se particles in nano-selenium composite packaging material in food simulants:Under the same migration temperature and time,migration order of nano-selenium particles in four food simulants was n-hexane,10%ethanol,4%acetic acid,distilled water.Migration mechanism of nano-selenium particles belonged to Fick diffusion,and diffusion coefficient increased with increase of migration temperature,while distribution coefficient decreased.Diffusion coefficient of selenium in n-hexane in nano-selenium composite packaging material was the largest and distribution coefficient was the smallest.4.Analysis on effect of keeping litchi,F.velutipes,tomato and pickled radish fresh with nano-selenium composite packaging material:Results of principal component analysis showed that,nine indexes,such as good fruit rate,quality loss rate and Vc of litchi,could be reduced to simplification.Dimension reduction was the first and second principal components which represent 95.325%comprehensive information of litchi fruit quality index.Fresh-keeping effect of nano-selenium composite packaging material on litchi fruits was better than that of common packaging material.Principal component analysis was used to analyze comprehensive changes of 8 indexes such as mass loss rate and titratable acid of tomato fruits in the early,middle and late stages of red ripening during storage at room temperature with nano-selenium composite packaging material.Two important principal components representing 90.183%comprehensive information of tomato fruit quality index in early red ripening stage,one important principal component representing 80.547%comprehensive information of tomato fruit quality index in middle red ripening stage and one important principal component representing 86.100%comprehensive information of tomato fruit quality index in late red ripening stage were determined.Storage period of tomato fruits in the early,middle and late stages of red ripening was about 12 days,9 days and 6 days respectively by principal component analysis,which was basically consistent with the actual storage test results.Compared with ordinary packaging material,nano-selenium composite packaging material had lower rot degree and browning degree of F.velutipes stored,which could effectively inhibit increase of respiratory intensity,MDA,cinnamyl alcohol dehydrogenase,POD etc.,as well as accumulation of lignin in vivo.Compared with ordinary packaging material,nano-selenium composite packaging material were more conducive to delaying the deterioration of pickled radish at 5,15,25 and 35?storage temperatures.Arrhenius equation,which took crispness,color difference and total bacteria quantity of pickled radish as quality evaluation indexes,had high fitting accuracy(R~2>0.95)with relative error of prediction value within 10%,and could well predict shelf life of pickled radish under different storage temperatures.In conclusion,nano-Se particles with an average particle size of 100 nm were biosynthesized by YL75,and nano-Se particles were used to prepare nano-selenium composite packaging material to explore effects of this packaging material on storage quality of fruits and vegetables.The study found that oxygen permeability,longitudinal tensile property and antibacterial property of nano-selenium composite packaging material,etc.were better than those of common packaging material.Nano-selenium composite packaging material has a beneficial effect on preservation of fruits and vegetables.What's more,this study could provide reference for development and application of nano-selenium in food packaging materials.