Method for preparing antibacterial edible films

[0040] Example 1

[0041] Using a stirring ball mill as the reaction device, a mechanical solid phase activation method is used for the ball milling reaction. Pullulan and ε-polylysine are used as raw materials. The mass ratio is 5:1.5, the mechanical activation time is 5 minutes, and the temperature is 25°C. , The stirring speed is 415r/min, and the grinding medium is a stainless steel grinding ball with φ5-10mm to prepare pullulan and ε-polylysine complex. Prepare the film-forming solution according to the ratio of the mass concentration of pullulan and ε-polylysine complex of 2g/100mL, gelatin of 5g/100mL, and glycerol of 1g/100mL: Gelatin was dissolved in distilled water at 80-90°C, and after cooling to 50-60°C, the complex of pullulan and ε-polylysine was added to dissolve, and glycerin was added after cooling to room temperature, stirred uniformly, and stirred magnetically for 10 minutes. The obtained film-forming solution is poured into a polypropylene petri dish, placed at room temperature to form a film for 8-10 hours, and dried in a natural environment to uncover the film to obtain the antibacterial edible film. After uncovering the film, equilibrate in a constant temperature and humidity test box at 40°C and a relative humidity of 50-55% for 2 days for subsequent testing of film properties (see Table 1).

[0042] Example 2

[0043] The stirring ball mill is used as the reaction device, and the mechanical solid phase activation method is used to carry out the ball milling reaction. Chitosan and ε-polylysine are used as raw materials. The mass ratio is 5:1.8, the mechanical activation time is 10min, and the temperature is 25℃. The stirring speed is 415 r/min, and a complex of chitosan and ε-polylysine is prepared. The film-forming solution was prepared according to the ratio of the mass concentration of the complex of chitosan and ε-polylysine of 2g/100mL, the mass concentration of gelatin of 5g/100mL, and the mass concentration of glycerol of 2g/100mL: first gelatin Dissolve in distilled water at 80~90℃, add the complex of chitosan and ε-polylysine to dissolve after cooling to 50~60℃, add glycerin after cooling to room temperature, stir evenly and magnetically stir for 10min. The film-forming solution is poured into a polypropylene culture dish, placed at room temperature to form a film for 8-10 hours, and dried in a natural environment to uncover the film to obtain the antibacterial edible film. After uncovering the film, equilibrate in a constant temperature and humidity test box at 40°C and a relative humidity of 50-55% for 2 days for subsequent testing of film properties (see Table 1).

[0044] Example 3

[0045] The stirring ball mill is used as the reaction device, and the mechanical solid phase activation method is used to carry out the ball milling reaction. The dextran and ε-polylysine are used as raw materials. The mass ratio is 5:2, the mechanical activation time is 8min, and the temperature is 25℃. The stirring speed is 415 r/min, and a complex of dextran and ε-polylysine is prepared. Prepare the film-forming solution according to the ratio of the mass concentration of the complex of dextran and ε-polylysine of 3g/100mL, the mass concentration of gelatin of 5g/100mL, and the mass concentration of glycerol of 1g/100mL: gelatin Dissolve in distilled water at 80-90°C, add the esterified compound of dextran and ε-polylysine after cooling to 50-60°C to dissolve, add glycerin after cooling to room temperature, stir evenly, and magnetically stir for 10 minutes. The film-forming solution is poured into a polypropylene culture dish, placed at room temperature to form a film for 8-10 hours, and dried in a natural environment to uncover the film to obtain the antibacterial edible film. After uncovering the film, equilibrate in a constant temperature and humidity test box at 40°C and a relative humidity of 50-55% for 2 days for subsequent testing of film properties (see Table 1).

[0046] Determination of the properties of edible films prepared in Examples 1 to 3

[0047] The film thickness is in accordance with GB/T6672-2001, and the thickness of each film is measured with a thickness gauge, and 13 points are uniformly taken (one point passes through the center of the film), and the average value is used as the film thickness value. The measurement of film thickness provides a basis for the determination of film performance indicators.

[0048] The mechanical properties of the film are measured according to the ASTM D882-01 method using a physical property tester to determine the tensile strength (TS, Tensilestrength) and the elongation at break (E, Elongationatbreak), the initial distance between the two probes is set to 40mm, and the pulling speed is set to 1mm /s. Its calculation refers to formulas 2-1 and 2-2.

[0049] TS=F/S2-1

[0050] E=(L 1 -L 0 )/L×100%2-2

[0051] In the formula: TS——tensile strength, MPa;

[0052] F——Maximum tensile force when the membrane is broken, N;

[0053] S——cross-sectional area of ​​membrane, m 2;

[0054] E——Elongation at break, %;

[0055] L 0 ——The length of the film sample, mm;

[0056] L l ——The length of the film at break, mm.

[0057] The water solubility of the film is cut into a 2cm×2cm film sample, and placed in a beaker filled with water at 90℃. It can be found that the film shrinks first and then disperses in the water in the form of many fine particles. The particle shape is the end point of the water dissolution time of this test, and the sample dissolution time (ST, Solubletime) is recorded.

[0058] The Water Vapor Permeability (WVP) test of the film is based on the principles and procedures of the water vapor permeability test method for plastic films and sheets, and the GB-1037-70 method is improved. The pseudo-cup method is adopted under the temperature condition of 25℃. Put anhydrous CaCl in the glass 2 (CaCl 2 Before use, it should be crushed to a particle size of 2mm, and dried in an oven at 200°C for 2h, and added to the glass after cooling) to make the added CaCl 2 Measure to 5mm of the cup mouth. Choose a uniform, non-porous, wrinkled film, measure its thickness with a micrometer, and then seal the film with melted paraffin and weigh it. Put the weighed glass cup into a desiccator with deionized water at the bottom at a temperature of 25°C (keep a relative humidity of 100%) to maintain a certain vapor pressure difference between the inside and outside of the membrane, and then take out the glass at regular intervals. Weigh, and calculate the water vapor transmission coefficient (WVP) value from this. Calculated according to the method of Aydindi and Kaya:

[0059] WVP=Δm×d/A×Δt×Δp

[0060] Where: WVP——water vapor transmission coefficient, g·m·(m 2 ·S·Pa) -1

[0061] Δm——increment of stable mass, g

[0062] A——The area of ​​the membrane, m 2

[0063] Δt——measurement time interval, s

[0064] d——the thickness of the film, m

[0065] Δp——The difference in water vapor pressure on both sides of the sample, Pa

[0066] Oxygen Barrier of the membrane is measured. Put 20.0g of fresh peanut oil in a container with a capacity of 250mL, cover the mouth of the container with different membrane samples and seal it, and then store it in a 60℃ incubator for 10 days. The peroxide value of peanut oil was determined by sodium thiosulfate titration method. According to the Peroxide Value (PV) of fats and oils, the oxygen barrier properties of edible film samples were evaluated. Determination of oil peroxide value: Weigh 2.00g~3.00g sample, put 30mL in a 250mL iodine bottle, add 30mL of chloroform-glacial acetic acid mixture to completely dissolve the sample, add 1.00mL saturated potassium iodide solution, tightly stopper Cap the bottle and shake it gently for 0.5 min. Place it in a dark place for 3 minutes, take out and add 100 mL of water, shake it, and titrate with sodium thiosulfate standard solution immediately. When it is light yellow, add 1 mL of starch indicator solution, continue titrating until the blue disappears as the end point, record the consumption, and Make a blank control.

[0067] X 2 =(V 2 -V 3 )×C 2 ×12.69/m 2

[0068] Where: X 2 ——Peroxide value in the sample, g/100g;

[0069] V 2 ——The volume of sodium thiosulfate standard solution consumed by the sample, mL;

[0070] V 3 ——The volume of sodium sulfate standard solution consumed by reagent blank, mL;

[0071] C 2 ——Concentration of sodium thiosulfate standard solution, mol/L;

[0072] m 2 ——The amount of the sample to be titrated, g.