Study On Preparation And Related Properties Of Smart Material Based On Mulberry Anthocyanins

Litchi（Litchi chinensis Sonn）is a plant in the family Amitaceae.Every year,more than one fifth of the total output of Litchi is produced in the world.Due to the limited preservation technology,it cannot bring economic value and causes huge economic losses.Intelligent packaging is a new type of packaging technology,which can perceive the content quality（such as maturity,freshness,etc.）through the identification of packaging material properties（such as color,etc.）under the condition of not destroying packaging.This experiment will chitosan（CS）and hydroxyethyl cellulose（HEC）of the membrane substrates,adding mulberry anthocyanins（MA）as a natural tracer,the preparation of the inner membrane liquid,add nano titanium dioxide（Nano-TiO₂）as a bacteriostatic agent,liquid preparation of outer membrane,in combination with flow extended to 3D printing technology,the preparation of antibacterial,keeping fresh,intelligent color as one of the double layer antibacterial chromogenic materials,through experiments to explore the basis of the material properties and the antibacterial fresh litchi fruit and freshness indicator effect,the main results were as follows:（1）In order to evaluate the properties of MA and its practical value as a freshness indicator in smart packaging materials,its ultraviolet spectrum characteristics,p H response and environmental stability were tested.The results show that the color of the MA solution changes from red to light red,blue and yellow-green when the p H value changes from 2 to 12,and the maximum absorption peak of UV-Vis spectrum gradually shifts to red.The changes of temperature,illumination and p H conditions have effects on the stability of MA.（2）In order to improve the stability of MA,CS/HEC mixed matrix was selected as the film substrate.Through the investigation of its apparent viscosity and 3D printing suitability,the optimal ratio of substrate was determined as CS:HEC=3:3（CH）,the CH viscosity was moderate,the printing process was consistent,not easy to break and clog,the printing image was of high stability,not easy to collapse and diffusion.Through the optimization of printing parameters,the optimal printing parameters of CH were determined step by step as follows:nozzle diameter 0.5 mm,printing pressure 30 k Pa,nozzle height 0.6 mm,and printing rate 30mm/s.（3）Nano-TiO₂ was added to CH to prepare the outer film by the flow method,and MA was added to CH.The inner film with different filling rates was printed on the outer film by 3D printing technology to prepare the double layer antibacterial chromogenic materials.Scanning electron microscopy and infrared spectroscopy showed that the intermolecular binding between the substances showed good compatibility.Nano-TiO₂ was evenly distributed in CH,and no agglomeration occurred.Of different double layer antibacterial chromogenic materials performance testing,the results show that the inner membrane fill rates affect overall performance,the inner membrane when the filling rate is 45%（CHMT-45%）,material performance is the best,the material thickness of 79.81 microns,the WVP of 4.73×10^-12g·cm/（cm²·s·Pa）,the tensile strength of 29.52 MPa,the elongation at break of 21.01%,on escherichia coli and staphylococcus aureus have strong inhibitory effect,under the different temperature,are showing strong color stability.（4）In order to explore double layer antibacterial chromogenic materials applied in the field of fruits and vegetables preservation and fresh instructions,to select the best CHMT-45%applied to the preservation of litchi fruit and intelligent color,the experimental results show that the double layer antibacterial chromogenic material can to a certain extent,extend the shelf life of litchi fruit,and to a certain extent determine litchi fruit freshness,the intelligent materials research and development has a certain reference value.