Study Of Rheological Behavior And Printability Of Chitosan-inorganic Pigments Based Edible Inks

Printing production and processing capacity in China have entered the forefront of the world.Traditional printing inks are mostly made of chemical raw materials,and thus have many problems.These harmful inks will affect human’s health（ink workers and printing workers）,affect the quality of packaging items（such as food）,and affect the environment of the air when inks are drying with volatile substances.The research and development of green inks is particularly important.There is some research about chitosan（with edible property,film-forming capacity and degradability）based edible inks that often use organic colorant.The research on chitosan molecular weight,inorganic pigment types and additive types for preparing edible ink is small.This thesis used the common chitosan（to reflect the universality of chitosan being applied in edible inks）and prepared chitosan-inorganic pigments based edible inks（fundamental-color and ordinary-color inks）:chitosan-iron oxide red based edible ink,chitosan-iron oxide yellow based edible ink,chitosan-TiO₂based edible ink,by green mechanical way（wet milling）.The effect of inorganic pigment contents on performance of primary edible inks was explored.The best ink formulation ranges were determined by Response Surface Method（RSM）.The main interaction among components in edible inks was hydrogen bond.These inks proved to be stable under different storage time and temperature.The rheological properties（viscosity,linear viscoelastic region,modulus,creep-recovery,etc.）of these chitosan-inorganic pigments based edible inks were explored.Microcosmic¯oscopic and physicochemical properties of chitosan-inorganic pigment based edible inks were firstly determined by SEM,BET,XRD,thermal analysis,etc.Then the rheological properties of these chitosan-inorganic pigments based edible inks were recorded by rheometer,and analyzed by experiment and by fitting&simulation of Matlab.The models included Cross equation,Burger’s model,etc.This procedure indicated the relationship between the ink structure（surface properties,structured level,elastic bonds,elastic strength）and printing（viscosity recover rate,printing resolution,dot gain）,predicted the print quality,and provided the theoretical basis for process design,manufacture and application of edible inks.Combined with rheological study,the obtained inks were then applied to flexographic printing and screen printing respectively.The best formulations for chitosan-inorganic pigments edible inks were determined:chitosan-iron oxide red based edible ink（the mass ratio of chitosan-3,edible iron oxide red pigment,acetic acid,ethyl alcohol,Tween 80 and soybean oil was 2:27.5:0.81:29.8:0.1:0.1）,chitosan-iron oxide yellow edible ink（the mass ration of chitosan-4,edible iron oxide yellow piment,and compositive additive was 5:11:1.45）,and chitosan-TiO₂ based edible ink（the mass ration of chitosan-4,TiO₂,and methylcellulose was 3:4.1:1）.The printing quality of these inks on the substrate proved to be excellent,which met the national standards and industry standards.This proved that these inks had good adaptability for flexographic printing and screen printing and were suitable for food decoration printing.The preparation&discussion methods of these edible inks could be applied to make new edible inks with other fundamental colors and other ordinary colors.The experiment showed that the prepared inks have wide application value in the field of ink,printing and food,with excellent market prospect.