Preparation And Properties Of Edible Packaging Films

Edible packaging film has a wide range of uses in food storage,transportation,etc.,and its role is to protect food from mechanical damage,control its physical,chemical and microbial activities.This thesis studies the preparation method of edible packaging film,systematically determines and quantifies various parameters and physical properties such as swelling degree,solubility,barrier property,tensile strength,elongation at break,water resistance and transparency of edible packaging film.And the application of edible packaging film in the preservation of fruits and vegetables.The test contents and results of this paper are as follows:1、Preparation of bleachable shellac edible film and study of its film forming properties.The bleached shellac was used as the research material,and its solubility in different concentrations of sodium bicarbonate solution,sodium carbonate solution and ethanol solution and the effect of different film-forming media on its film-forming properties were mainly explored.The results show that the higher the solvent concentration,the greater the solubility of bleached shellac.Under the same conditions,the solubility characteristics of bleached shellac in sodium carbonate solution and sodium bicarbonate solution are similar,and its solubility in ethanol solution is better than that in alkali solution.Much bigger.The bleached lac film obtained by low concentration alkali solution,ie 1.5% NaHCO3 solution,1.0% Na2CO3 solution and absolute ethanol,has a higher comprehensive score.The film-forming properties of bleached shellac film in different film-forming media are quite different: the alkali solution bleaching shellac film can be completely dissolved in water,but the solubility of anhydrous ethanol bleached shellac film is 0.02%,almost insoluble in water;alkali The larger the concentration of the solution,the larger the pH value of the membrane fluid,the greater the membrane permeability,the deeper the color,the smaller the transparency,the more brittle,the less smooth,the worse the mechanical properties;the higher the concentration of the aqueous ethanol solution,the smoother the membrane formed.The solubility and swelling degree are lower;the absolute ethanol membrane has a gas permeability of 0.99 um/(Pa·s)and a tensile strength of 0.4 MPa,which are all smaller than the alkali solution membrane;and the elongation elongation of the anhydrous ethanol membrane is 386.75%.,much larger than the alkali solution film.2、Preparation and application of oxalic acid/malic acid modified chitosan edible packaging film.Chitosan was cross-linked with oxalic acid and malic acid to improve the water resistance and mechanical properties of the chitosan edible packaging film.The infrared spectrum,viscosity and contact angle of the modified packaging film werecharacterized.Mode and mechanical properties,swelling degree and solubility,barrier properties,opacity and antibacterial properties,etc.,when the amount of oxalic acid added is0.6% or the amount of malic acid added is 0.8%,the water resistance of chitosan modified packaging film is obtained.The degree of swelling is significantly improved,the degree of swelling is at least 61%,the solubility is at least 12.2%,the elongation at break is up to73.4%,and the breaking strength is up to 5.1 MPa.The obtained two sets of modified packaging films were applied to the prune preservation.After the coating,the prune had a good change in appearance,and the weight loss rate and the respiratory intensity were significantly reduced.3、Preparation and application of blueberry edible packaging wrap film.Study agar and gelatin as film-forming substances,add glycerin,L-tartaric acid and natamycin to make blueberry edible packaging film with excellent antibacterial,anti-oxidation,water retention and anti-corrosion properties,and study the ratio of agar to gelatin.The effect of membrane gel temperature change and glycerol percentage,tartaric acid content and natamycin on membrane water retention performance,thereby optimizing the various properties of the membrane.The results showed that when the compounding ratio of agar and gelatin was 1:1,the film forming effect of the film liquid was better.Through the experiment of response surface,the optimal formula of blueberry edible packaging wrap film is 0.5g agar,0.5g gelatin,0.10 g glycerin,0.11 g tartaric acid,0.01 g natamycin,and the film is prepared by the formula.It can be used for fresh-keeping of blueberry coatings,and its preservation time can be extended by more than 6 days.