Preparation And Characterization Of Nanocellulose From Ginkgo Husk And Its Application In Edible Film

Ginkgo(Ginkgo biloba L.)originated in China.In 2015,the yield of ginkgo nut was 180 million tons,accounting for about 70% of the total yield in the world.The husk was usually burned directly or buried in the soil as agricultural waste,destroying the environment and wasting resources.Ginkgo husk shell has a high cellulose content(44.34%),which can be used as a potential source of nanocellulose.In this paper,ginkgo husk shell was used as raw material to prepare ginkgo husk shell nanocellulose,and the process optimization and characterization and its application in edible film were analyzed.The research results are as follows:1.Here the ultrasonic-assisted sulfuric acid hydrolysis method was used to prepare the nanocellulose from ginkgo husks,and the sulfuric acid mass fraction,reaction temperature and reaction time were used as influencing factors to conduct single factor and orthogonal experiments to obtain the optimal preparation conditions.Ginkgo husk nanocellulose prepared by conventional sulfuric acid hydrolysis method as a control,the effects of ultrasound-assisted processing on the nanocrystalline cellulose nut shell were analyzed by scanning electron microscope(SEM),transmission electron microscopy(TEM),Zeta potential and dynamic light scattering(DSC),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),Thermogravimetric analysis(TGA),etc.The results showed that the optimal preparation conditions of ginkgo husk nanocellulose are sulfuric acid content of 48%,reaction temperature of 60℃,reaction time of 25 min and the yield was 37.01%.The ginkgo nut shell nanocrystalline cellulose prepared by ultrasonic-assisted and normal sulfuric acid hydrolysis was long rod-shaped,and the length and diameter were 40-220 nm and 3.5-7.5 nm,respectively.However the range of length and diameter of nanocrystalline cellulose prepared by ultrasound-assisted method was relatively concentrated.The crystallinity of the nanocrystalline cellulose prepared by ultrasound was88%,which is higher than that of normal sulfuric acid hydrolysis nanocrystalline cellulose(75%).The nanocrystalline cellulose prepared by the two methods demostrated low zeta potential and good thermal stability.2.The effect of the addition amount of ginkgo husk shell nanocellulose on the film-forming properties of the edible film of lauric acid monoglyceride and soy protein isolate.The results show that in the range of 0%～1.0% nanocellulose addition,the tensile strength of edible film increases firstly and then decreases with the increase of nanocellulose.When the addition amount was 0.8%,the tensile strength reached the maximum value of 8.63 MPa.The elongation at break decreased firstly and then tended to be stable,and reached the minimum(36.00%)when the addition amount was 0.4%.Compared with the control group,the water vapor permeability(WVP)and the water solubility of the edible film gradually decreased,but the light transmittance,brightness(L*)and whiteness(W)increased.Through the analysis of fourier transform infrared spectroscopy(FT-IR),differential scanning calorimetry(DSC)and scanning electron microscopy(Scanning electron microscopy,SEM)of edible film found that edible membranes were mainly combined with each other through intermolecular hydrogen bonds and hydrophobic interactions.With the increase of nanocellulose,the melting onset temperature of the edible film has decreased.The surface of the edible film was relatively flat,and the internal gap is small.The cross-sectional structure was dense and there was no obvious cavity.3.Analysis of static rheology and dynamic rheology of the edible film liquid containing nanocellulose from ginkgo husk.The results show that in the range of 0% to 1.0% nanocellulose addition,with the increase of nanocellulose addition,the shear stress of the composite edible film liquid of different components gradually increased.With the increase of the shear rate increase,the shear stress continued to increase.Under the same shear rate,the shear stress of the control component was lower than the component containing nanocellulose.The composite edible membrane fluid is a shear thickened swelling plastic fluid.The dynamic rheological results of the composite edible membrane fluid showed that the addition of nanocellulose can increase the viscoelasticity of the edible membrane fluid to a certain extent.