| With the development of social science and technology and the improvement of human living standards,the use of packaging materials has also increased year by year,of which food packaging materials account for about two-thirds of the total.As most of the packaging materials are difficult to degrade,overuse not only causes"white pollution," but also increases the consumption of non-renewable resources such as petroleum and coal to some extent.Therefore,there is an urgent need to find a non-toxic and biodegradable food packaging film to replace the non-degradable petrochemical products currently used in large quantities.In this paper,according to the characteristics of carrageenan,its feasibility in food packaging and preservation of fruits and vegetables is studied.In this thesis,the composition of the selected Eucheuma was firstly analyzed,in which the moisture content was 13.62%and the ash content was 23.02%,indicating that the mineral content was abundant,while the protein and fat content was less,only 4.92%and 0.74%..The carrageenan was extracted by ultrasound-assisted method.The yield of carrageenan was 43.62%.The content of sulfate ester in the extracted carrageenan was 23.61%.In order to further determine the elements and content contained in carrageenan,elemental analysis was performed on the extracted carrageenan,in which the contents of H,C,N,O,and S were 6.18%,27.63%,0.03%,58.75%,and 6.26%respectively.,indicating that the polysaccharide structure and sulfate group and a very small amount of protein are mainly contained in the carrageenan;the analysis of the infrared spectrum of the carrageenan and the infrared spectrum of the commercially available kappa carrageenan are analyzed and compared,and the determination is made.Carrageenan is mainly K-carrageenan.Based on this caramel,an edible and biodegradable carrageenan food packaging film was prepared and the film was modified by CaCl2,MC and PEG400.The experimental results showed that the solid-liquid ratio was 1:75 and the concentration of CaCl2 solution was 0.5 mmol/L.When the contents of MC and PEG400 were both 0.5%,the mechanical properties of the blend membrane were the best,with a tensile strength of 34.21 MPa and a tensile elongation at break of 84.32%;SEM,FTIR,TG,and DMA.A variety of other means of characterizing the film change mechanism;SEM results show that the elongation of the blend film elongation increases;from the FITR can be seen that the blend film and no new substances are generated,so the judgment of the mixture of three substances is Physical mixing,carrageenan structure has not been destroyed;TG analysis showed that the addition of MC,PEG400 increased the thermal stability of the carrageenan base film;DMA data show that the Tg of the carrageenan-based blend film is 25 ?;It does not contain water-blocking substances,so WVP is large.In order to further improve the air permeability of the carrageenan-based blend membranes,the PVA-carrageenan-based bilayer membranes were investigated and their properties were characterized.The results showed that the 2.0%PVA membrane fluid concentration was 2.0%for all aspects of the performance of the composite membrane.All are good.The mechanical properties of the film were little different from those of the monolayer film of carrageenan.The tensile strength was 41.05 MPa,and the elongation at break was 80.21%.The composite SEM images at different temperatures showed that the composite film had a composite temperature of 60?.The spectrum shows that the interaction between the composite membranes is mainly hydrogen bonding and electrostatic interactions;the WVP of the composite membrane is reduced to 148.60 g/m2·Day compared to the monolayer membrane,and the oxygen permeability coefficient can be 5.29 cc/m2 · Day,this value can meet the requirements of some food packaging. |
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