Preparation Of Coconut Residue Nano Cellulose Composite Film And Its Application In Mango Preservation

Cocos nucifera L.is one of the pillar industries in Hainan.Coconut residue is the main leftover of coconut processing,which is often discarded(waste or even pollute the environment)or processed into feed(with low added value).In order to develop the utilization way of coconut residue and improve the benefit of coconut industry,this paper takes coconut residue cellulose as the research object,mainly studies the extraction process,nano treatment process,preparation of composite fresh-keeping film with coconut residue nano cellulose and its application in mango fresh-keeping,and the structure and composition of coconut residue cellulose were analyzed by modern instrument.The main results are as follows:(1)Comparative analysis of cellulose characteristics of coconut residue in four different oil extraction methods.Four different oil extraction methods,supercritical,subcritical,cold pressing and organic solvent extraction,were used to extract coconut residue as raw materials.Cellulose was obtained by subtraction.The structure was characterized by physical and chemical analysis(swelling power SWC,water holding WHC),as well as by scanning electron microscopy,infrared spectroscopy and X-ray diffraction.The results showed that there was no significant difference between the four degreasing methods in the yield of coconut residue cellulose,no significant difference in physical and chemical properties,and similar structure(loose appearance).Moreover,four different oil extraction methods will not cause great damage to the structure of coconut residue cellulose,so it can be concluded that the residual coconut residue of four different oil extraction methods can be used to extract cellulose.(2)Optimization of extraction process and determination of properties of nano-cellulose(CNC)from coconut residue.Taking the coconut residue cellulose purified by alkali pretreatment as the raw material,through the single factor and orthogonal experiments,aiming at the main factors such as sulfuric acid concentration,hydrolysis time(t),hydrolysis temperature(T),etc.,the extraction process of coconut residue cellulose by acid hydrolysis was studied and optimized,and the optimal technological conditions were obtained as follows:the concentration of H2SO4 is 65%,the time of sulfuric acid hydrolysis is 120 min,the temperature of sulfuric acid hydrolysis is 45 ?,and the yield of CNC is 56.72%.Coconut residue cellulose and original cellulose extracted by sulfuric acid hydrolysis retain the basic structure of original cellulose,so they also retain the basic characteristics of cellulose.Through physical and chemical analysis(SWC,WHC)and structural characterization(transmission electron microscope,Fourier infrared spectrum,x-ray diffraction),the CNC and standard nanocellulose hydrolyzed by sulfuric acid were compared and analyzed.The results show that the crystal structure and physical and chemical properties of CNC and standard nanocellulose are consistent,and the size of CNC reaches nanometer level by tem analysis.(3)Preparation and characterization of nano-cellulose composite membrane.Chitosan(CS)was used as matrix.Glycerin,apple polyphenol and nano cellulose(CNC)were added.The surface morphology of the composite membrane was observed by naked eye and scanning electron microscope.The mechanical properties,water vapor transmittance and oxygen resistance of the composite membrane were measured.The experimental results show that:with the increase of the amount of CNC added,the water vapor transmittance of CNC composite membrane decreased gradually.The peroxide value of oil decreased first and then increased with the increase of the amount of CNC in the cellulose composite membrane.When the amount of CNC was 4 g /100 ml,the oxygen resistance of the nanocellulose composite membrane was the strongest.The tensile strength,modulus and elongation at break of chitosan film without CNC were 45.4 MPa,1126 MPa and 5.22%,respectively.The tensile strength and elongation at break of the composite film increased from 0% to 4%,from 39.2 MPa to 45.4 MPa and 3.45% to 4.91%,respectively.(4)The effects of chitosan membrane,chitosan polyphenol membrane,chitosan CNC membrane and chitosan CNC polyphenol membrane on the surface morphology,hardness,weight loss rate,titratable acid content,soluble solids and respiratory intensity of mango were analyzed.The results showed that the titratable acid content(TTA),soluble solid content(SSC)and hardness of the four composite films decreased gradually during the storage of mango,among which the decline rate of mango in the experimental group of chitosan CNC polyphenol film preservation was the slowest,and the weight loss rate of mango in the experimental group of the composite film preservation was the lowest,and the respiratory intensity was the weakest,and the preservation effect was the best.