Preparation method of gallic acid mediated soybean protein isolate-hawthorn pectin composite film

Abstract

The invention discloses a preparation method of a gallic acid mediated soybean protein isolate-hawthorn pectin composite film, and belongs to the technical field of food packaging. The method comprises the following steps: 1, preparing a soybean protein isolate suspension; 2, gallic acid is introduced into the suspension liquid; step 3, adding hawthorn pectin under a water bath condition; step 4, adding glycerol into the mixed solution, and carrying out vacuum-assisted ultrasonic degassing to obtain a membrane solution; and step five, preparing the gallic acid mediated soybean protein isolate-hawthorn pectin composite film. The composite membrane is prepared by covalent crosslinking of gallic acid mediated soybean protein isolate and hawthorn pectin, and the performance of the membrane can be effectively improved. The composite film prepared by the method has good ductility and barrier ability and is biodegradable, the problem of environmental pollution is effectively solved, and a feasible scheme is provided for replacing traditional plastics. By measuring the tensile strength, the elongation, the light transmittance and the water vapor transmission coefficient, the composite film prepared by adding 1.0 g of gallic acid has the best performance.

Description

Technical Field

[0001] The present invention relates to a preparation method of gallic acid-mediated soy protein isolate-hawthorn pectin composite film, belonging to the technical field of food packaging. Background Art

[0002] Plastics are high molecular organic materials with synthetic resin as the main component, added with various additives, which can be molded into a certain shape under certain temperature and pressure and can maintain the established shape at room temperature. Because of their light weight, corrosion resistance and certain toughness, they are widely used in the packaging field. However, since it is difficult to degrade in the natural environment and is extremely easy to accumulate to form "white pollution", causing serious damage to the soil and ecological system, it is extremely urgent to develop new biodegradable packaging materials. Compared with traditional plastic packaging materials, the packaging materials prepared by the present invention can be naturally degraded, have excellent barrier and antibacterial properties and good biocompatibility. The basic raw materials are soy protein isolate and hawthorn pectin, and the raw material resources are rich, which is conducive to large-scale production.

[0003] Soy protein isolate is a high-quality protein extracted from soybeans, with a rich amino acid composition. The film prepared with it has high bioavailability and is safe and reliable, but its barrier ability is limited. In the present invention, hawthorn pectin, a kind of polysaccharide, is added as a thickener, which enhances the flexibility and barrier ability of the film. And hawthorn pectin contains various polyphenols such as catechins and active substances such as chlorogenic acid, endowing this film with natural antioxidant and antibacterial effects.

[0004] Gallic acid, also known as pentagallic acid, is an organic compound with multiple phenolic hydroxyl groups, having strong antioxidant and reactive activities. The phenolic hydroxyl groups of gallic acid form hydrogen bonds or covalent bonds with groups such as amino and carboxyl groups in soy protein molecules, and then interact with hydroxyl and carboxyl groups in hawthorn pectin molecules, thereby connecting soy protein and hawthorn pectin together and playing a role in mediating their combination. This mediating effect can optimize and complement the properties of soy protein and hawthorn pectin, thereby improving the properties of the film.

[0005] The composite film prepared by the present invention through gallic acid-mediated soy protein isolate-hawthorn pectin can effectively improve the antioxidant and antibacterial properties of the film, has good biocompatibility and strong barrier ability and is biodegradable, reducing environmental pollution while ensuring the extension of the food storage period. Summary of the Invention

[0006] The purpose of the present invention is to prepare a composite film with natural antibacterial, antioxidant ability and good biocompatibility through gallic acid-mediated soy protein isolate-hawthorn pectin, break the barrier of traditional plastic films, and produce a new type of food packaging material with excellent barrier ability and biodegradability.

[0007] The object of the present invention is achieved by the following technical solutions:

[0008] A preparation method of gallic acid-mediated soy protein isolate-hawthorn pectin composite film, the method comprising the following steps:

[0009] (1) Take 3.0 g of soy protein isolate powder, add it to 100 mL of deionized water, stir well to form a suspension, and adjust the pH of the suspension to 9.0 with 0.1 M NaOH solution; (2) Add solid gallic acid to the suspension, stir magnetically for 30 min, and adjust the pH of the mixed solution to 7.0; (3) Place the solution obtained in step (2) in a dialysis bag and dialyze it in deionized water for 48 h; (4) After stirring the dialyzed solution at 70 °C for 2 h, add 2.0 g of hawthorn pectin to completely dissolve it; (5) Add 2.0 mL of glycerol as a plasticizer under magnetic stirring at 70 °C to obtain a Pickering emulsion; (6) Remove bubbles by vacuum-assisted ultrasonic treatment for 20 min to obtain a composite film solution; (7) Take 25 mL of the film-forming solution and pour it evenly into a petri dish with a diameter of 15 cm to cast a film, and dry it at 25 °C for 3 d; (8) Peel the dried film and store it at 25 °C and a relative humidity of 50% for 48 h. Description of the Drawings

[0010] Figure 1 . A preparation flow chart of gallic acid-mediated soy protein isolate-hawthorn pectin composite film;

[0011] Figure 2 . Tensile strength and elongation at break of the composite film under different gallic acid addition amounts;

[0012] Figure 3 . Water vapor transmission coefficient and light transmittance of the composite film under different gallic acid addition amounts. Detailed Embodiments

[0013] The following further illustrates the present invention with specific embodiments, but the present invention is not limited by the embodiments. The main raw materials, reagents and experimental equipment used in the following embodiments are as follows:

[0014] Main raw materials and reagents: soy protein isolate powder, solid gallic acid, hawthorn pectin, glycerol, NaOH solution, deionized water;

[0015] Experimental equipment: constant temperature water bath, oven, constant temperature and humidity chamber.

[0016] Example 1:

[0017] (1) Weigh 3.0 g of soy protein isolate powder and add it to 100 mL of deionized water. Stir well to form a suspension, and adjust the pH of the suspension to 9.0 with 0.1 M NaOH solution. (2) Add 0.5 g of gallic acid solid to the suspension, stir magnetically for 30 min, and adjust the pH of the mixed solution to 7.0. (3) Place the solution obtained in step (2) into a dialysis bag and dialyze it in deionized water for 48 h. (4) After stirring the dialyzed solution at 70 °C for 2 h, add 2.0 g of hawthorn pectin to dissolve it completely. (5) Add 2.0 mL of glycerol as a plasticizer under magnetic stirring at 70 °C to obtain a Pickering emulsion. (6) Remove the bubbles by vacuum-assisted ultrasonic treatment for 20 min to obtain a composite film solution. (7) Take 25 mL of the film-forming solution and pour it evenly into a petri dish with a diameter of 15 cm to form a film by casting, and dry it at 25 °C for 3 days. (8) Peel off the dried film and store it at 25 °C and a relative humidity of 50% for 48 h.

[0018] Example 2:

[0019] (1) Weigh 3.0 g of soy protein isolate powder and add it to 100 mL of deionized water. Stir well to form a suspension, and adjust the pH of the suspension to 9.0 with 0.1 M NaOH solution. (2) Add 1.0 g of gallic acid solid to the suspension, stir magnetically for 30 min, and adjust the pH of the mixed solution to 7.0. (3) Place the solution obtained in step (2) into a dialysis bag and dialyze it in deionized water for 48 h. (4) After stirring the dialyzed solution at 70 °C for 2 h, add 2.0 g of hawthorn pectin to dissolve it completely. (5) Add 2.0 mL of glycerol as a plasticizer under magnetic stirring at 70 °C to obtain a Pickering emulsion. (6) Remove the bubbles by vacuum-assisted ultrasonic treatment for 20 min to obtain a composite film solution. (7) Take 25 mL of the film-forming solution and pour it evenly into a petri dish with a diameter of 15 cm to form a film by casting, and dry it at 25 °C for 3 days. (8) Peel off the dried film and store it at 25 °C and a relative humidity of 50% for 48 h.

[0020] Example 3:

[0021] (1) Take 3.0 g of soy protein isolate powder and add it to 100 mL of deionized water. Stir well to form a suspension, and adjust the pH of the suspension to 9.0 with 0.1 M NaOH solution. (2) Add 1.5 g of gallic acid solid to the suspension, stir magnetically for 30 min, and adjust the pH of the mixed solution to 7.0. (3) Place the solution obtained in step (2) in a dialysis bag and dialyze it in deionized water for 48 h. (4) After stirring the dialyzed solution at 70 °C for 2 h, add 2.0 g of hawthorn pectin to dissolve it completely. (5) Add 2.0 mL of glycerol as a plasticizer under magnetic stirring at 70 °C to obtain a Pickering emulsion. (6) Remove the bubbles by vacuum-assisted ultrasonic treatment for 20 min to obtain a composite film solution. (7) Take 25 mL of the film-forming solution and pour it evenly into a petri dish with a diameter of 15 cm to cast a film, and dry it at 25 °C for 3 d. (8) Peel off the dried film and store it under the conditions of 25 °C and 50% relative humidity for 48 h.

[0022] Control group:

[0023] Commercially available soy protein isolate film.

[0024] Table 1 Comparison of performance effects of each example

[0025] It can be analyzed from the table that gallic acid forms hydrogen bonds or covalent bonds with soy protein molecules, and then interacts with hawthorn pectin, thus connecting soy protein and hawthorn pectin together, playing a role in mediating their combination. The addition of gallic acid significantly improves the performance of the composite film. It can be known from the experimental data analysis that the composite film prepared by adding 1 g of gallic acid solid has the best performance.

[0026] The above has elaborated on the present invention and its specific embodiments. The actual embodiments are not limited thereto. For those of ordinary skill in the art, referring to the examples of the present invention, there will be changes in the specific embodiments and application scopes; however, without departing from the purpose of the present invention, similar embodiments should be within the protection scope of the present invention.

Claims

1. A method for preparing a gallic acid-mediated soy protein isolate-hawthorn pectin composite film, characterized in that: The composite film comprises the following steps:

1. Take 3.0 g of soy protein isolate powder, add it to 100 mL of deionized water, stir thoroughly to form a suspension, and adjust the pH of the suspension to 9.0 with 0.1 M NaOH solution; 2. Add gallic acid solid to the suspension, stir magnetically for 30 minutes, and adjust the pH of the mixed solution to 7.0; 3. Place the solution obtained in step 2 in a dialysis bag and dialyze in deionized water for 48 hours; Fourth, stir the dialyzed solution at 70°C for 2 hours, then add 2.0 g of hawthorn pectin to completely dissolve it; 5. Add 2.0 mL of glycerol as a plasticizer under magnetic stirring at 70 °C to obtain a Pickering emulsion; 6. Vacuum-assisted ultrasonic treatment for 20 min to remove bubbles and obtain a composite membrane solution; 7. Take 25 mL of the film-forming solution and pour it evenly into a culture dish with a diameter of 15 cm to form a film, and dry it at 25°C for 3 days; 8. Peel off the dried film and store it at 25°C and 50% relative humidity for 48 hours.

2. The method for preparing a gallic acid-mediated soy protein isolate-hawthorn pectin composite film according to claim 1, characterized in that: The purity of the soy protein isolate powder in step 1 is 93%.

3. The method for preparing a gallic acid-mediated soy protein isolate-hawthorn pectin composite film according to claim 1, characterized in that: The amount of gallic acid solid added in step 2 is 0.8-1.0 g.

4. The method for preparing a gallic acid-mediated soy protein isolate-hawthorn pectin composite film according to claim 1, characterized in that: The molecular weight cut-off of the dialysis bag in step 3 is 3500–5000 Da.

5. The method for preparing a gallic acid-mediated soy protein isolate-hawthorn pectin composite film according to claim 1, characterized in that: The concentration of hawthorn pectin in step 4 is 13%.

6. The method for preparing a gallic acid-mediated soy protein isolate-hawthorn pectin composite film according to claim 1, characterized in that: In step 5, 2.0-2.5 mL of glycerol was added under magnetic stirring at 70°C.

7. The method for preparing a gallic acid-mediated soy protein isolate-hawthorn pectin composite film according to claim 1, characterized in that: The power of the vacuum-assisted ultrasonic treatment in step six is ​​between 100W and 500W.

8. The method for preparing a gallic acid-mediated soy protein isolate-hawthorn pectin composite film according to claim 1, characterized in that: The drying temperature in step seven is 20°C-25°C, and the drying time is not less than 3 days.

9. The method for preparing a gallic acid-mediated soy protein isolate-hawthorn pectin composite film according to claim 1, characterized in that: In step eight, the dried film is peeled off and stored at 25° C. and a relative humidity of 50%-55% for 48 hours.

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