CN101445615B - Soyabean protein/dialdehyde starch/nano silver composite membrane, preparation method and application thereof - Google Patents

Abstract

The invention discloses a soybean protein/dialdehyde starch/nano-silver composite film with antibacterial function and a preparation method. Soybean protein/dialdehyde starch/nano-silver composite film is prepared by solution casting method, soybean protein and plasticizer glycerin are dispersed in water, then soybean protein aqueous solution is mixed with dialdehyde starch and silver nitrate solution evenly, After casting, it is baked to form a film. During the process of film formation, the aldehyde group on the dialdehyde starch and the amino group on the soybean protein have a cross-linking reaction, and at the same time, the aldehyde group reduces the silver ion in situ to form silver nanoparticles. The invention also discloses the application of the composite film as food packaging material and medical material. The soybean protein/dialdehyde starch/nano-silver composite film has good mechanical properties and antibacterial properties, and can be rapidly degraded in natural environment.

Description

Soybean protein/dialdehyde starch/nano-silver composite film and its preparation method and application

technical field

The invention belongs to the field of polymer packaging materials, and in particular relates to a packaging film with soybean protein and dialdehyde starch as the matrix—soy protein/dialdehyde starch/nano-silver composite film, which has excellent mechanical properties and antibacterial properties.

Background technique

The quality and safety of food has always been a matter of great concern to food companies and consumers. The traditional polyethylene packaging film can only temporarily isolate food contamination from external bacteria, but cannot prevent the reproduction of bacteria in the packaging system. At the same time, the degradation rate of polyethylene materials in nature is slow, and a large amount of use will also bring harm to the environment. Huge pollution. Therefore, the research and development of degradable packaging film with antibacterial function has very important practical significance.

As far as the antibacterial mechanism is concerned, the current preparation of antibacterial packaging films is mainly to directly add some substances with antibacterial function to the film-forming matrix, and the film will continuously release antibacterial substances to the food surface in contact with it. Preservation of food. Chinese patent ZL01137391.1 prepared a kind of packaging film with antibacterial function by blending zinc chloride into polyolefin raw materials; Chinese patent ZL200720116439.3 prepared a three-layer structure poly Ethylene antibacterial film, mixed with nano-silver particles with antibacterial function between polyethylene films. Compared with other inorganic particles, nano-silver particles have broad-spectrum antibacterial properties and strong antibacterial ability. The existence of nano-silver particles will affect the bacteria. Respiration and normal metabolic functions cause the cell wall of bacteria to rupture, thereby killing bacteria and achieving the purpose of antibacterial.

Soybean protein is a kind of natural polymer isolated and extracted from soybean, which has very good film-forming properties. The film made of soybean protein has many advantages such as edible, non-toxic, low oxygen permeability, and low price. It can be well degraded in nature. Because soybean protein molecules contain many hydrophilic groups such as amino groups and carboxyl groups, compared with polyolefin materials, pure soybean protein films are still insufficient in terms of strength and water resistance. Cross-linking modification is an effective method to improve the properties of soybean protein materials. Currently commonly used cross-linking agents are: formaldehyde, acetaldehyde, glutaraldehyde and transglutaminase. Chinese patent ZL02138823.7 uses formaldehyde to cross-link soybean protein to prepare a class of soybean protein fiber with excellent air permeability and dyeability; Chinese patent application CN1676015A uses transglutaminase to cross-link soybean protein. Under the action of aminoamidase, some peptide bonds in soybean protein molecules are broken to form amino and carboxyl groups. At the same time, the enzyme can promote the formation of new peptide bonds between amino groups and carboxyl groups in protein molecules. The generation of peptide bonds enhances the interaction between protein molecules. Therefore, the comprehensive performance of the material can be greatly improved.

Due to the high toxicity and volatilization of small molecule aldehydes, and the high price of transglutaminase and the difficulty of obtaining large quantities, the application of protein films in the fields of food packaging and medical materials is greatly limited.

Contents of the invention

In order to solve the deficiencies of the above-mentioned prior art, the primary purpose of the present invention is to provide a soybean protein/dialdehyde starch/nano-silver composite film with antibacterial function. The present invention first synthesizes a kind of starch with aldehyde groups on the molecular chain—dialdehyde starch. Dialdehyde starch was used as a cross-linking agent to modify soybean protein by cross-linking, and at the same time, the aldehyde group on dialdehyde starch was used to reduce Ag ⁺ into nano-silver particles in situ, and the method of solution casting to form a film was used to prepare soybean protein/dialdehyde Aldehyde starch/nanosilver composite film. The composite film has excellent mechanical properties and antibacterial properties, and can be rapidly degraded in nature.

The purpose of the present invention is achieved through the following technical solutions, a preparation method of soybean protein/dialdehyde starch/nano-silver composite film, comprising the steps:

(1) Soluble starch is oxidized by sodium periodate to obtain dialdehyde starch:

Dissolve 10 g of soluble starch in 100 mL of NaIO solution with a concentration of 0.2 mol/L to 0.8 mol/ _L , adjust the pH to 2 to 4 with acid, then react at 0 to 30 ° C for 2 to 6 hours in the dark, and use Precipitate with acetone, wash with deionized water until neutral, and obtain dialdehyde starch after freeze-drying.

(2) Soybean protein/dialdehyde starch/nano-silver composite film was prepared by solution casting method.

Disperse soybean protein and plasticizer glycerol in water at 60-90°C to obtain soybean protein aqueous solution. After cooling to room temperature, dissolve dialdehyde starch in soybean protein aqueous solution, and then drop silver nitrate solution under stirring Add it to the soybean protein aqueous solution, and control the amount of silver to be 0.5% to 5% of the soybean protein mass to obtain a soybean protein casting liquid. The soybean protein casting liquid is cast in a mold, and after baking to form a film, the soybean protein/dialdehyde Starch/nanosilver composite film.

In order to better realize the present invention, in step (1), the acid is preferably 1mol/L sulfuric acid.

In step (2), the plasticizer glycerol accounts for 20-30% of the soybean protein; the dialdehyde starch accounts for 10-30% of the soybean protein. The concentration of the silver nitrate solution is 0.1mol/L. The solid content of the soybean protein casting solution is 8% to 15%; the baking film is formed by using an infrared lamp to bake the film.

The thickness of the soybean protein/dialdehyde starch/nano-silver composite film is between 0.1-0.25um, the diameter of the silver particles in the composite film is between 30nm-60nm, and the amount of the silver particles is controlled to be 0.5%-5% of the soybean protein quality. %.

A soybean protein/dialdehyde starch/nano-silver composite film is prepared by the above method.

The soybean protein/dialdehyde starch/nano-silver composite film of the present invention has good antibacterial performance, and the antibacterial rate against Escherichia coli is about 93% to 96%, and is suitable for use in the fields of food packaging materials and medical materials.

Using soybean protein as the matrix, a series of degradable food packaging films were prepared by solution casting film formation. Dialdehyde starches with different aldehyde content were used to modify the soybean protein by cross-linking. The mechanical strength and The water resistance has been significantly improved. At the same time, the aldehyde group on the dialdehyde starch is used to reduce Ag ⁺ into silver particles in situ. Scanning electron microscope observations show that the diameter of the silver particles is between 30nm and 60nm (see Figure 1).

Compared with the prior art, the present invention has the following advantages and beneficial effects:

The present invention uses a non-volatile macromolecule aldehyde crosslinking agent——dialdehyde starch to crosslink and modify soybean protein, thereby improving the mechanical properties and water resistance of the protein film, and at the same time utilizing the aldehyde group on the dialdehyde starch to Ag ⁺ is reduced into nano-silver particles in situ. The existence of nano-silver particles endows the soybean protein film with good antibacterial properties. The prepared soybean protein/dialdehyde starch/nano-silver composite film has very broad applications in the fields of food packaging and medical materials. application prospects.

Compared with the method of simply blending nano-silver particles, the present invention utilizes the aldehyde group on the dialdehyde starch to reduce Ag ⁺ into nano-silver particles in situ, which is more conducive to obtaining a uniformly dispersed nano-composite material. At the same time, compared with polyolefin packaging films, soybean protein/dialdehyde starch/nano-silver composite films can be well degraded in nature and will not pollute the environment.

The bacterial classification that soybean protein/dialdehyde starch/nano-silver composite film antibacterial performance test prepared by the present invention adopts is escherichia coli ATCC 8099, and antibacterial test is by QB/T 2591-2003 " antibacterial plastics——antibacterial performance test method and antibacterial effect ", the antibacterial rate of the film is about 93% to 96%, indicating that the soybean protein/dialdehyde starch/nano-silver composite film has excellent antibacterial properties.

Description of drawings

Fig. 1 is the scanning electron micrograph of the section of the soybean protein/dialdehyde starch/nano-Ag composite film of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Example 1

(1) Sodium periodate is used to oxidize soluble starch to obtain dialdehyde starch. Dissolve 10g of soluble starch in 100mL _NaIO4 solution with a concentration of 0.2mol/L, adjust the pH to 2 with 1mol/L sulfuric acid, and then react at 20°C in the dark for 4h, precipitate the product with acetone, and then use deionized After washing with water to neutrality, the dialdehyde starch was obtained after freeze-drying, which was marked as DAS1.

(2) Add 10 g of soybean protein, 3 g of glycerol and 150 mL of distilled water into the reaction kettle, stir and disperse at room temperature for 30 minutes, then raise the temperature to 70 ° C, stir and disperse vigorously for 30 minutes to obtain a uniform and stable soybean protein aqueous solution. Cool to room temperature (25°C-35°C), dissolve dialdehyde starch (DAS1), which accounts for 10% of the soybean protein mass, into the soybean protein aqueous solution under vigorous stirring, and simultaneously add a silver nitrate solution with a concentration of 0.1mol/L to the In the reaction kettle, the consumption of silver is controlled to be 1% of the soybean protein quality to obtain a soybean protein casting solution, the solid content of the soybean protein casting solution is 8%, and then the soybean protein casting solution is cast into a polytetrafluoroethylene mold, and the infrared The lamp is baked to form a film to obtain a soybean protein/dialdehyde starch/nano-silver composite film. The thickness of this composite film is 0.15 ± 0.02um, the diameter of silver particles in the composite film is between 30nm～60nm (as shown in Figure 1), the tensile strength of the composite film is 5 ± 0.9MPa, and the antibacterial rate to Escherichia coli 93% to 96%, the composite film can be completely degraded after being buried in the soil for 60 days.

Example 2

(1) Sodium periodate is used to oxidize soluble starch to obtain dialdehyde starch. Dissolve 10g of soluble starch in 100mL _NaIO4 solution with a concentration of 0.5mol/L, adjust the pH to 3 with 1mol/L sulfuric acid, and then react at 20°C in the dark for 4h, precipitate the product with acetone, and then use deionized Washed with water until neutral, freeze-dried to obtain dialdehyde starch, marked as DAS2.

(2) Add 10 g of soybean protein, 3 g of glycerol and 150 mL of distilled water into the reaction kettle, stir and disperse at room temperature for 30 minutes, then raise the temperature to 60 ° C, stir and disperse vigorously for 30 minutes to obtain a uniform and stable soybean protein aqueous solution. Cool to room temperature, dissolve the dialdehyde starch (DAS2) that accounts for 20% of the soybean protein mass into the soybean protein aqueous solution under vigorous stirring, and simultaneously add the silver nitrate solution with a concentration of 0.1mol/L dropwise into the reactor to control the concentration of silver. The dosage is 3% of the soybean protein mass to obtain a soybean protein casting solution, the solid content of the soybean protein casting solution is 15%, and then the soybean protein casting solution is cast into a polytetrafluoroethylene mold, and baked by an infrared lamp to form a film to obtain Soybean protein/dialdehyde starch/nano-silver composite film. The thickness of the composite film is 0.2 ± 0.02um, the diameter of the silver particles in the composite film is between 30nm and 60nm, the tensile strength of the composite film is 5 ± 0.9MPa, and the antibacterial rate to Escherichia coli is 93% to 96%. The film can be completely degraded after being buried in soil for 60 days.

Example 3

(1) Sodium periodate is used to oxidize soluble starch to obtain dialdehyde starch. Dissolve 10g of soluble starch in 100mL _NaIO4 solution with a concentration of 0.8mol/L, adjust the pH to 2 with 1mol/L sulfuric acid, and then react at 20°C in the dark for 4h, precipitate the product with acetone, and then use deionized After washing with water to neutrality, the dialdehyde starch was obtained after freeze-drying, which was marked as DAS3.

(2) Add 10 g of soybean protein, 3 g of glycerol and 150 mL of distilled water into the reaction kettle, stir and disperse at room temperature for 30 minutes, then raise the temperature to 90 ° C, stir and disperse vigorously for 30 minutes to obtain a uniform and stable soybean protein aqueous solution. Cool to room temperature, dissolve the dialdehyde starch (DAS3) that accounts for 30% of the soybean protein mass into the soybean protein aqueous solution under vigorous stirring, and simultaneously add the silver nitrate solution with a concentration of 0.1mol/L dropwise into the reactor to control the concentration of silver. The dosage is 4% of the soybean protein mass to obtain a soybean protein casting solution, the solid content of the soybean protein casting solution is 10%, and then the soybean protein casting solution is cast into a polytetrafluoroethylene mold, and baked by an infrared lamp to form a film to obtain Soybean protein/dialdehyde starch/nano-silver composite film. The thickness of the composite film is 0.2 ± 0.02um, the diameter of the silver particles in the composite film is between 30nm and 60nm, the tensile strength of the composite film is 5 ± 0.9MPa, and the antibacterial rate to Escherichia coli is 93% to 96%. The film can be completely degraded after being buried in soil for 60 days.

Example 4

(1) Sodium periodate is used to oxidize soluble starch to obtain dialdehyde starch. Dissolve 10g of soluble starch in 100mL _NaIO4 solution with a concentration of 0.5mol/L, adjust the pH to 3 with 1mol/L sulfuric acid, and then react at 30°C in the dark for 2h, precipitate the product with acetone, and then use deionized Washed with water until neutral, freeze-dried to obtain dialdehyde starch, marked as DAS2.

(2) Add 10 g of soybean protein, 2 g of glycerol and 150 mL of distilled water into the reaction kettle, stir and disperse at room temperature for 30 minutes, then raise the temperature to 70 ° C, stir and disperse vigorously for 30 minutes to obtain a uniform and stable soybean protein aqueous solution. Cool to room temperature, dissolve the dialdehyde starch (DAS2) that accounts for 20% of the soybean protein mass into the soybean protein aqueous solution under vigorous stirring, and simultaneously add the silver nitrate solution with a concentration of 0.1mol/L dropwise into the reactor to control the concentration of silver. The dosage is 5% of the soybean protein mass to obtain a soybean protein casting solution, the solid content of the soybean protein casting solution is 12%, and then the soybean protein casting solution is cast into a polytetrafluoroethylene mold, and an infrared lamp is used to bake to form a film to obtain Soybean protein/dialdehyde starch/nano-silver composite film. The thickness of the composite film is 0.15±0.02um, the diameter of the silver particles in the composite film is between 30nm and 60nm, the tensile strength of the composite film is 3 to 6MPa, and the antibacterial rate to Escherichia coli is 93% to 99.5%. It can be completely degraded after being buried in the soil for 60 days.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (10)

1. a preparation method of soybean protein/dialdehyde starch/nano-silver composite film, is characterized in that comprising the steps: (1) Soluble starch is oxidized by sodium periodate to obtain dialdehyde starch: Dissolve 10 g of soluble starch in 100 mL of NaIO solution with a concentration of 0.2 mol/L to 0.8 mol/ _L , adjust the pH to 2 to 4 with acid, then react at 0 to 30 ° C for 2 to 6 hours in the dark, and use Precipitate with acetone, wash with deionized water until neutral, and obtain dialdehyde starch after freeze-drying; (2) Prepare soybean protein/dialdehyde starch/nano-silver composite film by solution casting film-forming method: Disperse soybean protein and plasticizer glycerol in water at 60-90°C to obtain soybean protein aqueous solution. After cooling to room temperature, dissolve dialdehyde starch in soybean protein aqueous solution, and then drop silver nitrate solution under stirring Add it to the soybean protein aqueous solution, and control the amount of silver to be 0.5% to 5% of the soybean protein mass to obtain a soybean protein casting liquid. The soybean protein casting liquid is cast in a mold, and after baking to form a film, the soybean protein/dialdehyde Starch/nanosilver composite film. 2. the preparation method of a kind of soybean protein/dialdehyde starch/nano-silver composite film according to claim 1, is characterized in that: in step (1), described acid is the sulfuric acid of 1mol/L. 3. the preparation method of a kind of soybean protein/dialdehyde starch/nanometer silver composite film according to claim 1 is characterized in that: in step (2), described plasticizer glycerin is 20% of soybean protein quality ~30%. 4. the preparation method of a kind of soybean protein/dialdehyde starch/nano-silver composite film according to claim 1, is characterized in that: in step (2), described dialdehyde starch accounts for 10～30% of soybean protein quality . 5. The preparation method of a kind of soybean protein/dialdehyde starch/nano-silver composite film according to claim 1, characterized in that: in step (2), the concentration of the silver nitrate solution is 0.1mol/L. 6. The preparation method of a soybean protein/dialdehyde starch/nano-silver composite film according to claim 1, characterized in that: in step (2), the solid content of the soybean protein casting solution is 8% to 15% %. 7. the preparation method of a kind of soybean protein/dialdehyde starch/nano-silver composite film according to claim 1, is characterized in that: in step (2), described baking film-forming is to adopt infrared lamp to bake film-forming . 8. The preparation method of a soybean protein/dialdehyde starch/nano-silver composite film according to claim 1, characterized in that: the thickness of the soybean protein/dialdehyde starch/nano-silver composite film is 0.1-0.25um The diameter of the silver particles in the composite film is between 30nm and 60nm. 9. A soybean protein/dialdehyde starch/nano-silver composite film prepared by the method according to any one of claims 1-8. 10. the application of soybean protein/dialdehyde starch/nano-silver composite film described in claim 9 in the packaging material of food or medical material field.