Fabrication Of Moistureproof Konjac Glucomannan Films With Fruit-cuticle-like Property

Seeking alternative renewable petroleum resources is extremely urgent because extensive use of synthetic polymer packaging materials has caused serious problems of environmental pollution.In recent years,in view of more attention has been paid to konjac glucomannan(KGM)gradually,the research and development of KGM film-based material has become an essential direction in the field of green packaging.However,since KGM films are high in hygroscopic property and low in waterproof property,it is unable for them to meet the moistureproof demand of food in the storage and packaging.Hence the application and development of KGM packaging films are restricted.Based on imitating the water-resistant fruit cuticle,the moisture-resistant coated films were prepared by applying shellac/stearic acid coating onto both sides of dKGM films.The main research conclusions are divided into the following parts.The surface microstructure of fruit cuticles had much to do with the shape of epidermis cell,surface structure of cell and multicellular structures formed in epidermis.And the diversity of cuticles microstructure varied from fruit species.In the process of enzymolysis of fruit cuticle,the wax material outside cuticle was easily destructable and hard to observe.Shellac adhered to the surface of KGM films significantly reduced the WVP of KGM films,indicating that bilayer films was credited with moistureproof property.However,bilayer surface was still easier to be wetted by water.In addition,tensile strength(?b),elongation at break(?b)and elastic modulus(E)of bilayer films were reduced in different levels.That's partially because the adhesion between KGM film and shellac were physical adhesion which was not strong enough.When stearic acid content in the coating layer increased 20 to 40 wt%,the moisture resistivity,contact angle,and the tensile strength,modulus and elongation at break of the coated films were much higher than those of dKGM and dKGM-SSAO films.The shellac in coating layer contributed to improving optical transmittance of the coated films,while stearic acid in coated films played an important role in enhancing surface hydrophobicity,mechanical properties.Finally,the regression analysis showed that there was a positive linear correlation between water content of wheat flour and the storage time both for the coated films and PE films.It was worth noting that the rate of increasing water content of wheat flour sealed with coated films and PE fillms were 0.127 and 0.139,respectively.In addition,the water content of wheat flour sealed with the coated films exceeded the national standard(no more than 14.5%)in the 10th days,while the PE film in the 13th days,proving that the coated films with certain moisture resistance had potential to storage food,which was comparable to PE films.