Study On The Modified Membranes Of Konjak Glucomannan And Application In The Fresh-Keeping Of Longan

Nowdays plastic membranes are becoming main fresh-keeping ones,but they are non-degradable and have toxic and side effects to the health in humans.The study on the paper products and degradable plastic has achieved great progress,but they are too far to practicable use.There we should seek degradable and safety materials with the excellent performance of plastic.The polysaccharide membrane could be a good alternative and could be paid more attention.In this study konjak glucomannan material was used as a substrate,nano-CaCO₃ as an inorganic filler to improve the modified membrane,various properties of fresh-keeping membranes were examined.The best membrane forming technique was achieved:Key data to confirm the critical technique and parameters of the membraneing in laboratory were offered as follows:(1)Compared with unpured konjac powder membrane,the pure konjac powder membrane has better tensile strength.It also has better folding ability.The reason is that intermolecular hydrogen bonds number is enhanced.(2)Nano- CaCO₃ was treated with anionic surfactant detergent to prepare KGM/ nano- CaCO₃ dioxide modified membranes,the membranes were characterized by FTIR.The result showed that there was hydrogen bonding intrractions between KGM and CaCO₃ dioxide nanoparticles.Nano- CaCO₃ was prepared and used to modify thin membranes,the effect of nano- CaCO₃ adding amounts on membranes' permeation and mechanical properties were studied.The results showed that nano- CaCO₃ could disperse into membranes symmetrial;as the amount of nano- CaCO₃ increased,the mechanical properties increase firstly and then decrease,but the gas permeation rate decreased gradually.(3)From comprehensive analysis,compared to the KGM membrane the tensile strength of the modified membrane increases 75%,the breaking elongation increase 46%,the tearing strength increase 30%.And the gas permeation rate decreased gradually when KGM 0.8g,glycerin 1.0ml,nano- CaCO₃ 0.2g.(4)The membrane forming technology of modified membrane was studied.The dynamic equation of tensile strength:Y=66.78799+5.04480X₁-12.48120X₂+4.52821X₃-3.88635X₁²-3.88812X₂² +3.26000X₁X₃+2.92750X₂X₃,the dynamic equation of the breaking elongation:Y=66.78799+5.04480X₁-12.48120X₂+4.52821X₃-3.88635X₁²-3.88812X₂² +3.26000X₁X₃ +2.92750X₂X₃the dynamic equation of water vapor transmission rate:Y=5.39303+0.35901X₁-1.12013X₂+0.42341X₃-0.28403X₁²-0.37241X₂² +0.34292X₁X₃ (5)Abstraction,mechanical action and delete thermal effect intensify spatial networks structure,improve tensile strength and water vapour permeability properties,but decrease elongation.The tensile strength was 98.68MPa,elongation 21.34%and the tearing strength was 98.68MPa when the output power was 30W and the treatment time was 15 min.(6)Comparing the effects of several membrane materials,it showed that modified membrane can reduce the physiological reaction,avoid anaerobic respiration.During the storage period,the sound fruit rate reached 86.4%,water loss rate,respiration were reduced significantly and the dissolvable substance delete,total acid delete,Vc could be well protected.The activities of PPO,POD,SOD were also be effectively restrained.The commercial value was enhanced.