Study On Galactomannan-based Food Packaging Film

Today,discarded plastic packaging waste poses a serious threat to the survival of life on Earth,and the development of degradable plastic alternatives is imminent.In this paper,the galactomannan(GM)as raw material,acetic anhydride(AA)as hydrophobic modifier,deacetylated chitin(DE-Ch N)as enhancer,nano zinc oxide(Nanometer zinc oxide,nano-Zn O)as a functional modifier were prepared for the fabrication of the GM-based food packaging film.At the same time,the application of galactomannan-based food packaging film in preservation was also explored.The effects of AA,DE-Ch N,and nano-Zn O additions on the mechanical properties of GM film materials,oxygen and water vapor transmission rate,ultraviolet transmission,hydrophobicity,cell compatibility and antibacterial properties were studied.The microstructure,molecular structure and thermal stability of GM before and after modification were characterized and analyzed by a variety of detection and characterization methods.Through the above performance test,the optimal addition amount of AA,DE-Ch N and nano-Zn O in GM were determined.In addition,the application of nano-Zn O and GM composite film to the preservation of fruits were also studied.(1)Since the GM chain contains a large number of hydroxyl groups,the composed films were hydrophilic,which can furtherly be obtained through AA esterification.By measuring the degree of esterification and hydrophobicity of GM after reaction,the optimal addition amount of AA in the esterification reaction was determined.When the reaction ratio of AA to GM was 1.5:1(w/w),the degree of esterification was the highest,and the water contact angle was increased by47%compared to the original GM film.The tensile strength was also maximized,which was42%higher than the original GM film.The esterified GM film maintained the original thermal stability and was non-toxic to RAW 264.7 cell(Mouse monocyte macrophages).Moreover,the oxygen barrier performance of the GM film was better than the high-density polyethylene(HDPE)plastic film on the market.(2)The mechanical properties of the GM film alone are poor;but the mechanical properties of the GM film can be improved by adding DE-Ch N.The effects of different DE-Ch N additions on the mechanical properties,hydrophobicity and antibacterial properties of GM membranes were studied.When the addition amount of DE-Ch N was 60%(W/W,GM dry weight),the maximum tensile strength of the obtained DE-Ch N and GM composite film was increased by 245%,and the hydrophobicity was increased by 48%,and it had no toxicity to macrophages.The composite film also showed good antibacterial properties against Escherichia coli and Bacillus subtilis.(3)In order to prepare antibacterial GM films,nano-Zn O was used as a functional modifier to study the mechanical properties,hydrophobicity,water vapor,oxygen transmission rate,and ultraviolet transmission rate and thermal stability of GM-based film with different nano-Zn O content.When the addition amount of nano-Zn O was 10%(W/W,GM dry weight),the obtained nano-Zn O/GM composite film showed excellent hydrophobicity,with a contact angle of 108~o,which is 48%higher than the original GM films,and absorbed 99%or more of UVA and UVB.The minimum tensile strength of the composite film(25MPa)was higher than that of the HDPE plastic film(17MPa),and its oxygen barrier performance was better than that of the polyethylene(PVC)plastic film.The composite membrane also showed good antibacterial properties against Escherichia coli and Bacillus subtilis.It also had antibacterial effect on the preservation of fruits.Therefore,combining nano-Zn O with renewable and sustainable packaging materials to prepare packaging materials with antibacterial properties will provide a new way for food aseptic packaging.GM functional packaging materials based on renewable biomass show great development potential as a sustainable alternative to petrochemical sources of plastics.