Preparation And Performance Characterization Of Polysaccharide Based Food Contact Materials

Polysaccharide is a kind of natural macromolecular compound,which is a polymer combining glycosidic bond with aldose or ketose.They exist in algae,higher plants,fungi,and animals,and are the most common biopolymers in nature.Polysaccharide have been used as bio-polymeric materials such as sodium alginate,pectin,carrageenan,agar,chitosan,etc,which are one of the sustainable materials used in the study of edible coating and composite film in recent years.Most polysaccharide raw materials have excellent film forming,safety and non-toxic,biodegradable and so on.Among them,sodium alginate solution has good biocompatibility and can form a stable three-dimensional network structure by cross-linking with Ca²⁺,which is used as the theoretical basis of this experiment to carry out experimental research.In this paper,food contact materials are prepared with polysaccharide raw materials.Using the good film formation and water resistance of calcium alginate,the compound film is combined with other polysaccharide raw materials to prepare the seaweed glue composite film,which can be applied to edible straws.Considering the poor mechanical properties of pure calcium alginate film,it can be compounded with paper to prepare seaweed glue composite paper,which can not only improve the mechanical properties of the film,but also solve the problem of low wetness of paper.For paper straws,it can also reduce the"paper"taste problem of paper straws.Using a single factor experiment enhance the mechanical properties and water resistance of the straw materials of seaweed glue straw materials.The criterion of judgment of materials are tensile strength,elongation at break,swelling degree and water solubility as the criteria for determining the material’s optimal ratio,and improving the water resistance.The orthogonal experiment selects the high-G sodium alginate as the raw material to optimize.For food-contact paper,sodium alginate solution is used as impregnation solution and CaCl₂as crosslinking agent.The paper studies the enhancement effect on the wet strength of paper,and measure paper’s other properties.For enhancing the other properties besides wet strength and enlarging the application range of paper,chitosan emulsified wax was selected in the experiment to prepare the impregnation solution,which acted on the surface of paper to reduce the moisture absorption,improve the stiffness of paper,dry tensile strength and other properties.The main findings are as follows:1、The experiment adopts solvent evaporation method,sodium alginate,pectin,starch,agar,sucrose and glycerol are used as raw materials,CaCl₂solution is used as crosslinking agent.The experiment use single factor experiment to prepare films.The final ratio was as follows:water of 100 g,sodium alginate of 3 g,agar of 2 g,pectin of 0.5g,starch of 1 g,glycerol of 3 g,CaCl₂ of 5%,crosslinking time of 7 min,the final composite film thickness is 0.417mm,tensile strength is 38.88MPa,elongation at break is 31.05%,water solubility is 27.12%and the swelling degree is 129.54%.The composite film formed by this condition has good mechanical properties,but the water resistance is poor,and it loses strength and swelling degree after soaking in water.2、The experiment selectes high-G sodium alginate as raw material,and optimize the raw material ratio of edible alginate composite film by single factor test and response surface method.The final ratio is:water of 100 g,sodium alginate of 1.75 g,agar of 2 g,pectin of 0.5 g,starch of1 g,glycerol of 5 g,CaCl₂ of 4%,crosslinking time of 5 min.The final measured composite film thickness is 0.317 mm,tensile strength is 23.16 MPa,elongation at break is 30.08%,water solubility is 31.07%,and swelling degree is 101.11%.Under this condition,the composite film has good mechanical properties and water resistance,which can maintain the integrity after soaking in hot water,and the swelling degree of the film decreases obviously.3、The experiment selectes pure wood pulp paper as the base paper and sodium alginate of high G segment as raw material to prepare the impregnation solution.The impregnated paper was crosslinked by CaCl₂ solution to prepare composite paper with certain wet strength.When the concentration of sodium alginate is 0.3%and CaCl₂ is 3%,the optimum wet strength index of the paper is 10.17 N·m·g^-1,the amount of glue is 1.01 g·m^-2,the bending resistance is 429 times,and the breaking resistance is 5.52 KPa·m²·g^-1.For the alginate hydrophilicity,the dry tensile strength and stiffness of the prepared paper are poor,and the Cobb value is low.4、The experiment uses palm wax and beeswax in cationic and chitosan as raw materials to prepare the chitosan-beeswax-palm wax emulsion.The prepared seaweed gum composite paper was impregnated with the wax emulsion,and then heat treated to melt the wax particles and cover the fiber surface or pores.The study found that the paper after sizing and heat treatment at 80℃has good liquid resistance,and futher enhance the wet tensile index of the paper.At the same time,it improves the dry tensile index,stiffness,Cobb value and other properties of paper.Taking beeswax:Palm wax ratio of 7:3 mixed wax emulsion,comparing the physical properties of the paper after heat treatment at 80 with unglued paper,the results show that the Cobb value of the paper has been reduced from 56.94 g·m^-2to 11.80 g·m^-2,the straightness of the paper is 0.503 m N·m,and the dry tensile index is 101.62 N·m·g^-1.