Preparation And Application Of Deacetylated Konjac Glucomannan/Black Rice Dietary Fiber Composite Film

Konjac glucomannan(KGM)is a natural polysaccharide with the highest viscosity extracted from Amorphophallus konjac.It is widely used in food packaging because of its biodegradability and excellent film forming performance.However,KGM film is easy to absorb water and has low mechanical strength,which limits its application in food preservation.Generally,the properties of KGM films can be improved by mixing KGM with natural or synthetic polymers,or by modifying KGM.In this study,the KGM/BRDF composite film was prepared by adding black rice dietary fiber(BRDF)to the KGM as the skeleton material,and then the KGM/BRDF composite film was modified by removing the acetyl group,so as to modify the KGM/BRDF composite film.The modified composite film was applied to the preservation of blueberries.The main research contents and results are as follows:Preparation and characterization of KGM/BRDF composite membrane.With KGM and BRDF as raw materials,oregano essential oil was loaded with vermiculite.On the basis of single factor test,the preparation process of KGM/BRDF composite membrane was optimized by orthogonal test,that is,0.37 g of KGM,0.074 g of BRDF,0.60 g of glycerine and 0.074 g of vermiculite were added to 100 mL distilled water.Under this condition,the tensile strength of KGM/BRDF composite membrane was 11.15±0.19MPa,elongation at break 36±1.3%,water solubility 42±1.4%The water vapor transmission coefficient is 0.59±0.07 g·mm/m~2·h·k Pa,and the transparency is 2.7 mm.When the content of oregano essential oil is 12μL/mL,the compound membrane solution can inhibit the proliferation of Staphylococcus aureus and Escherichia coli;The results of infrared scanning spectrum showed that the intermolecular hydrogen bond interaction in the composite membrane was enhanced;SEM results showed that BRDF increased the crosslinking degree of the composite membrane,formed a dense network structure,and the pores in the cross section disappeared.Preparation and characterization of Da-KGM/BRDF composite membrane.The KGM was deacetylated to obtain Da-KGM.The Da-KGM/BRDF composite membrane was prepared by tape casting and blending with BRDF.The preparation process of the Da-KGM/BRDF composite membrane was optimized by response surface methodology,that is,0.2%Da-KGM0.37 g,BRDF 0.074 g,glycerin 0.50 g,vermiculite0.074 g were added to every 100 mL of distilled water.Under this condition,the tensile strength of the composite membrane is 12.67±0.13 MPa,the elongation at break was30±1.7%,the water solubility was 37±1.2%,and the water vapor transmission coefficient was 0.35±0.03 g·mm/m~2·h·k Pa.The results of infrared scanning spectrum showed that KGM was deacetylated successfully,and the intermolecular interaction of Da-KGM/BRDF composite membrane was enhanced compared with Da-KGM film.The scanning electron microscope results show that compared with the KGM/BRDF composite film,the cross section of the Da-KGM/BRDF composite film is smoother and more uniform,forming a denser network structure.Da-KGM/BRDF composite film and KGM/BRDF composite film for the preservation of blueberries.Taking PE film as control,Da-KGM/BRDF composite film and KGM/BRDF composite film were used for the preservation of blueberries.The results showed that Da-KGM/BRDF composite film treatment group had lower decay rate and weight loss rate of blueberries,less loss of soluble solids,vitamin C and total acid content,less mildew,shrinkage and softening of blueberries,and could maintain good color and low decay rate.The preservation effect was better than that of KGM/BRDF composite film.