Preparation method of high-performance soy protein emulsion film

Abstract

The application relates to a preparation method of a high-performance soy protein emulsion film, which comprises the following steps: carrying out fiberization denaturation on soy protein by adopting an acetic acid-water binary solution, so that the hydrophobic performance, film forming capacity and environmental interference resistance of the soy protein can be remarkably improved; and further starting from the protein self-assembly fiberization principle and the protein film forming theory, the protein molecules are self-assembled and fiberized in the water solution, so that a soy protein-based biological film with certain mechanical strength and flexibility is constructed, and the problems of poor mechanical performance and high solubility of the current protein-based biological film are effectively solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of food packaging, and relates to a preparation technology of edible film, in particular to a preparation method of high-performance soy protein emulsion film. BACKGROUND

[0002] Soy protein has various biological functions, such as good biocompatibility, degradability and nutritional characteristics, and has great potential in replacing petroleum-based film materials. However, soy protein often exhibits poor mechanical properties and barrier properties when constructing film materials, and the construction and stabilization of the film materials have always been a difficult problem to break through in the field.

[0003] Chinese Patent Publication No. CN113308002A discloses a preparation method of a protein edible film. Protein is used as the main raw material, and sodium chloride, potassium chloride, lysine, arginine, histidine, cysteine and ascorbic acid are dissolved to prepare a Chaotropic ion solution, and then an edible film is further prepared. However, the tensile strength of the soy protein edible film prepared by the method is only 2.2 MPa, the solubility of the film is 89.5%, the preparation process is complex and the cost is high, and the mechanical property of the film is not obviously improved.

[0004] Chinese Patent Publication No. CN111154128B discloses an antibacterial and antioxidant whey protein isolate edible film and a preparation method thereof. The whey protein isolate is used as the main film-forming matrix, and is combined with bamboo leaf antioxidant, sodium caseinate, and a plasticizer. The whey protein isolate edible film is prepared through the steps of mixing, heat denaturation, vacuum degassing, flat plate flow, drying and film stripping. However, the elongation at break of the whey protein edible film prepared by the invention is only about 32%.

[0005] In summary, the existing preparation methods of protein-based edible films still have problems such as poor performance, insecurity and high cost. Therefore, it is an urgent problem in the field of food packaging to find a preparation method of protein edible film with simple process, low cost, good performance and low biological toxicity. SUMMARY

[0006] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a preparation method of high-performance soy protein emulsion film with high ductility, high barrier property and high safety, which can effectively improve the hydrophilic and hydrophobic properties and film-forming ability of protein, thereby increasing the mechanical properties of the edible film.

[0007] The technical problem of the present application is solved by adopting the following technical scheme:

[0008] A preparation method of high-performance soy protein emulsion film, comprising the following steps:

[0009] S1, 2-4wt% soybean protein isolate powder is added into a binary mixed solvent of acetic acid and water with pH of 2.0-3.0, stirred and dissolved to obtain an acidified protein solution;

[0010] S2, the protein solution prepared in step S1 is packaged in a sealed glass container and heated in a constant temperature water bath at 65-95℃ for 1-6h, and then the solution is cooled to obtain a soybean protein isolate fibrous solution;

[0011] S3, plant essential oil is added to the soybean protein isolate fibrous solution prepared in step S2, with a mass ratio of 1:3-1:6, and then homogenized at a speed of 12000rpm for 3min using a high-speed homogenizing disperser, and then degassed in an ultrasonic machine for 3min to obtain a protein fiber emulsion;

[0012] S4, 2.0-6.0wt% polyvinyl alcohol and 10%-50% solid glycerol are added to the protein fiber emulsion prepared in step S3 according to a mass ratio of 1-5:0.4-3.2, and stirred uniformly to prepare a film-forming solution,

[0013] S5, the film-forming solution prepared in step S4 is poured into a glass tank covered with a polytetrafluoroethylene film, and a fresh-keeping film with a plurality of holes is covered on the surface of the glass tank to control the evaporation rate of the acid solvent, and dried at RH 40%, 25℃ for 24h to obtain a soy protein edible film.

[0014] Moreover, the protein in the protein powder is a globular protein, including but not limited to soybean protein isolate, bovine serum albumin, whey protein, pea protein, lysozyme.

[0015] Moreover, the concentration of the acetic acid solution is 30-50% by volume.

[0016] Moreover, the concentration of the acetic acid solution is 40% by volume.

[0017] Moreover, the plant essential oil is tea tree essential oil.

[0018] Moreover, lauric acid or benzoic acid is added to the plant essential oil.

[0019] Moreover, the added amount is 1-10wt% of the plant essential oil.

[0020] The advantages and positive effects of the present application are:

[0021] 1, the present application introduces a binary weak acid-acetic acid, and uses acetic acid treatment to induce protein denaturation, which can produce a large number of β-sheet structures, and realizes the improvement of the hydrophobicity of the protein-based biological film.

[0022] 2、The polyvinyl alcohol is added to form a double network structure to improve the flexibility and elongation at break of the edible film, and the important stability of the dispersion system, i.e., electrostatic steric hindrance and hydrogen bonding, is innovatively applied to the construction and stability of the protein fiber-based biological film, so that the flexibility and stability of the edible film are improved.

[0023] 3、The plant essential oil is added to improve the antibacterial activity and antioxidant activity of the emulsion edible film, so that the food is protected from microbial contamination.

[0024] 4、The preparation method is simple, safe, low in cost and energy consumption, controllable in operation, and suitable for large-scale industrial production and processing, so that the method has wide application space in the food, daily chemical product and other industries.

[0025] 5、The soybean protein is denatured by using an acetic acid-water binary solution, so that the hydrophobic property, film forming capacity and environmental interference resistance of the soybean protein are significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The figures are atomic force microscope images of soybean protein isolate and soybean protein isolate amyloid fibers, wherein A1 and A2 are soybean protein isolate globulin, and B1 and B2 are soybean protein isolate amyloid fibers.

[0027] Figure 2 The figures are optical microscope images and appearance diagrams of soybean protein isolate emulsion and soybean protein isolate amyloid fiber emulsion, wherein A1 and B1 are natural soybean protein isolate emulsion, and A2 and B2 are soybean protein isolate amyloid fiber emulsion.

[0028] Figure 3 The figures are scanning electron microscope images of the present application embodiment 3 and the control example 3, wherein A1 and A2 are respectively the plan view and the cross-sectional view of the prepared emulsion edible film when the mass concentration of the natural soybean protein isolate (without acid heat treatment) is 4wt%, and the volume fraction of acetic acid is 40% (v / v); and B1 and B2 are respectively the plan view and the cross-sectional view of the prepared emulsion edible film when the mass concentration of the soybean protein isolate amyloid fiber is 4wt%, and the volume fraction of acetic acid is 40% (v / v).

[0029] Figure 4 The figures are appearance diagrams of the protein emulsion edible film of the control examples 1-3.

[0030] Figure 5 Appearance of protein emulsion edible films of embodiments 1-7 of the present invention. DETAILED DESCRIPTION

[0031] The present application is further described in detail by the following specific examples, which are only illustrative and not restrictive, and cannot limit the protection scope of the present application.

[0032] The principle of the present application is that under the action of acid heat, proteins form stable amyloid fibers rich in β-sheet structure by means of non-covalent bond forces such as intermolecular hydrogen bond, hydrophobic interaction, π-π interaction, etc. This fiber structure has the characteristics of high stability and high hydrophobicity, and the fiberization deformation is irreversible, thereby exhibiting excellent material properties. For example, the fiberized denatured protein produced by whey protein at pH = 2.0, 90℃ water bath for 5h can be used to prepare a transparent, flexible biodegradable film. If a water-soluble polymer substance is added to the protein solution in advance, a plastic film can be further formed for fruit and vegetable packaging.

[0033] Acetic acid belongs to a binary weak acid, which can slowly ionize more hydrogen ions at the same pH, which helps the formation of intermolecular hydrogen bonds and promotes the flexibility of the film. Through the principle of protein fiber assembly, the present application deeply explores the regulation method of acetic acid-induced fiberization transformation to improve the film-forming ability and stability of proteins, and masters the preparation method of related high-performance protein emulsion edible films. Therefore, the establishment of this method can overcome the key limitations of water solubility and stability of protein film materials in industrial applications.

[0034] Example 1

[0035] Film formation of soybean 7S protein powder under the conditions of protein concentration of 2wt% and acetic acid volume fraction of 40%.

[0036] The method for extracting and separating soybean 7S protein components comprises the following steps:

[0037] (1) The low-temperature defatted soybean powder is dispersed in deionized water according to the solid-liquid ratio of 1:15, and the dispersion is slowly adjusted to pH = 7.5 with 2 mol / L NaOH solution, and stirred for 2h to ensure that the protein in the soybean powder is fully dissolved.

[0038] (2) Centrifugation (9000xg, 30min) at room temperature to remove insoluble substances, and the supernatant is added with NaCl to adjust the ionic concentration to 0.25mol / L, stirred uniformly and restored to room temperature, and the solution pH is adjusted to 5.4 again, and low-temperature centrifugation (9000xg, 30min) is performed again and the supernatant is collected.

[0039] (3) The collected supernatant is diluted with 2 volumes of deionized water, the pH is adjusted to 4.8 again, centrifuged (6500 x g, 20 min) and the precipitate is collected.

[0040] (4) Finally, the collected protein precipitate is redispersed with deionized water, the pH of the dispersion is adjusted to 7.5, the dispersion is stirred until completely dissolved, the redissolved protein solution is loaded into a dialysis bag (8-14 kDa molecular weight cut-off), dialyzed for 48 h with water changed once in 12 h, and freeze-dried to obtain the 7S soy protein component.

[0041] A preparation method of a high-performance edible soybean 7S protein film, comprising the following steps:

[0042] S1, accurately weigh 2 g of soybean 7S protein powder, disperse it in 100 g of a 40% acetic acid-water solution, seal the bottle opening with tin foil paper, continuously stir in a 85℃ water bath for 5 h, then cool in ice water, and obtain a soybean 7S isolated protein fibrillation solution with a mass concentration of 2 wt%;

[0043] S2, add 1.5 ml of plant essential oil (tea tree essential oil) to the soybean 7S isolated protein fibrillation solution, use a high-speed homogenizing disperser to homogenize at a speed of 12000 rpm for 3 min, then degas in an ultrasonic machine for 3 min to obtain a protein fiber emulsion, measure 2 g of polyvinyl alcohol and 0.6 g of glycerol, add them to the above solution, and stir uniformly to obtain a film-forming solution;

[0044] S3, take 30 mL of the film-forming solution and pour it into a glass tank (10 cm x 12 cm) coated with a polytetrafluoroethylene film, cover the surface of the glass tank with a preservative film pierced with a plurality of holes to control the evaporation rate of the acid solvent, dry at RH 40%, 25℃ for 24 h to obtain a soybean 7S protein edible film.

[0045] As shown in Table 1, in the case of adding only glycerol and polyvinyl alcohol as plasticizers, the thickness of the soybean 7S protein edible film of the present embodiment can reach 95.8 μm, the tensile strength can reach 8.5 MPa, the elongation at break can reach 80.57%, the moisture permeability can reach 0.6851 x 10 -3 g·mm / m 2 ·h·KPa, and the film solubility is as low as 29.8%.

[0046] Example 2

[0047] The film-forming conditions of soybean 11S protein powder under the conditions of a protein concentration of 2 wt% and an acetic acid volume fraction of 40%.

[0048] A soybean 11S protein component extraction and separation method, comprising the following steps:

[0049] (1) Low-temperature defatted soybean flour was dispersed in deionized water at a solid-liquid ratio of 1:15, and the dispersion was slowly adjusted to pH 7.5 with 2 mol / L NaOH solution and stirred for 2 h to ensure that the protein in the soybean flour was fully dissolved.

[0050] (2) Centrifuge at room temperature (9000 × g, 30 min) to remove insoluble matter. Add 1.04 g / L NaHSO3 powder to the supernatant, and adjust the pH of the supernatant to 6.4 with 2 mol / L HCl solution. Then transfer the supernatant to a 4°C refrigerator for acid precipitation overnight. The next day, centrifuge at 4°C to obtain a precipitate.

[0051] (3) The protein precipitate was washed twice with deionized water and redispersed in deionized water, placed in a dialysis bag (molecular weight cutoff of 8-14 kDa), dialyzed for 48 h, with the water changed every 12 h, and freeze-dried to obtain the 11S soybean protein fraction.

[0052] A method for preparing a high-performance soybean 11S protein edible film comprises the following steps:

[0053] S1. According to the method described in Example 1, 2 g of soybean 11S protein powder was accurately weighed and dispersed in 100 g of a 40% by volume acetic acid-water solution. The bottle was sealed with tin foil and stirred continuously in an 85°C water bath for 5 h. The mixture was then cooled in ice water to obtain a soybean 11S protein isolate fiberization solution with a mass concentration of 2 wt%;

[0054] S2, 1.5ml of plant essential oil (rose essential oil) was added to the soybean 11S protein isolate fibrillation solution, and the solution was homogenized for 3min using a high-speed homogenizer at a speed of 12000rpm, and then placed in an ultrasonic machine for degassing for 3min to obtain a protein fiber emulsion. 2g of polyvinyl alcohol and 0.6g of glycerol were measured and added to the above solution, and stirred to obtain a film-forming solution.

[0055] S3. Pour 30 mL of the film-forming liquid into a glass tank (10 cm × 12 cm) lined with polytetrafluoroethylene film. Cover the surface of the glass tank with a layer of plastic wrap pierced with several holes to control the evaporation rate of the acid solvent. Dry at RH 40% and 25°C for 24 h to obtain the soybean 11S protein edible film.

[0056] As shown in Table 1, in this embodiment, when only glycerol and polyvinyl alcohol are added as plasticizers, the thickness of the soybean 11S protein edible film can reach 96.2 μm, the tensile strength can reach 10.2 MPa, the elongation at break can reach 72.83%, and the moisture permeability can reach 0.6251×10 -3 g·mm / m 2 ·h·KPa, the film solubility is as low as 25.2%.

[0057] Example 3

[0058] Effect of mixed ratio of 7S and 11S soybean proteins as raw material on edible film properties

[0059] An edible film of soybean protein isolate was prepared according to the method described in Example 1.

[0060] A method for preparing a high-performance soy protein emulsion film, comprising the following steps:

[0061] S1, accurately weigh 1g of soybean 7S protein powder and 1g of soybean 11S protein powder (soybean protein isolate powder) respectively, disperse them in 100g of 40% acetic acid-water solution, seal the bottle mouth with tin foil paper, continuously stir in a 85℃ water bath for 5h, then cool in ice water, obtain a soybean protein isolate fiberized solution with a mass concentration of 2wt%;

[0062] S2, add 1.5ml of plant essential oil (tea tree essential oil) to the soybean protein isolate fiberized solution, use a high-speed homogenizing disperser to homogenize at a speed of 12000rpm for 3min, then degas in an ultrasonic machine for 3min to obtain a protein fiber emulsion, measure 2g of polyvinyl alcohol and 0.6g of glycerol and add them to the above solution, stir uniformly to obtain a film-forming solution;

[0063] S3, take 30mL of the film-forming solution and pour it into a glass tank (10cm×12cm) coated with a polytetrafluoroethylene film, cover the surface of the glass tank with a preservative film with several holes to control the evaporation rate of the acid solvent, dry at RH 40%, 25℃ for 24h to obtain a protein edible film.

[0064] As shown in Table 1, this embodiment investigates the effect of the mixed ratio of 7S and 11S soybean proteins as raw material on the edible film, and the results show that the mixed ratio of the two proteins has an enhancing effect on the tensile strength and barrier properties of the edible film.

[0065] Among them, the microstructure diagram (atomic force microscope) of natural soybean protein isolate and soybean protein isolate amyloid fiber is as shown in Figure 1 It is observed that the natural soybean protein isolate with a size of 20-400nm has a spherical structure, and the height is about 0.8-3.9nm; after 5h of heat treatment at 85℃, the soybean protein isolate self-assembles to form a large number of short rod-like fibers with a length of about 250 to 600nm and a height of about 1.5nm.

[0066] The optical microscope images and appearance diagrams of the soybean protein isolate emulsion and the soybean protein isolate amyloid fiber emulsion are as shown in Figure 2As shown in the figure, A1 is an optical microscope image of a natural soybean protein isolate emulsion, B1 is an appearance image of a natural soybean protein isolate emulsion, A2 is an optical microscope image of a soybean protein isolate amyloid fiber emulsion, and B2 is an appearance image of a soybean protein isolate amyloid fiber emulsion.

[0067] Example 4

[0068] Effect of protein concentration on edible film properties

[0069] A method for preparing a high-performance soy protein emulsion film, comprising the following steps:

[0070] S1, accurately weigh 2g of soybean 7S protein powder and 2g of soybean 11S protein powder (soybean protein isolate powder) respectively, disperse them in 100g of a 40% by volume acetic acid-water solution, seal the bottle opening with tin foil paper, continuously stir in a 85℃ water bath for 5h, then cool in ice water, obtain a soybean protein isolate fiberization solution with a mass concentration of 4wt%;

[0071] S2, add 1.5ml of plant essential oil to the soybean protein isolate fiberization solution, use a high-speed homogenizing disperser to homogenize at a speed of 12000rpm for 3min, then degas in an ultrasonic machine for 3min to obtain a protein fiber emulsion, measure 2g of polyvinyl alcohol and 0.9g of glycerol and add them to the above solution, stir uniformly to obtain a film-forming solution;

[0072] S3, take 30mL of the film-forming solution and pour it into a glass tank (10cm×12cm) coated with a polytetrafluoroethylene film, cover the surface of the glass tank with a preservative film with several holes to control the evaporation rate of the acid solvent, dry at RH40%, 25℃ for 24h to obtain a protein edible film.

[0073] As shown in Table 1, this embodiment investigates the effect of protein concentration on the edible film, and the results show that the increase of protein concentration has a strengthening effect on the tensile strength of the edible film.

[0074] Example 5

[0075] Effect of polyvinyl alcohol addition ratio on edible film properties

[0076] According to the method described in Example 3, a soybean protein isolate edible film is prepared.

[0077] A method for preparing a high-performance soy protein emulsion film, comprising the following steps:

[0078] S1, accurately weigh 4g of soybean protein isolate powder, disperse it in 100g of a 40% by volume acetic acid-water solution, seal the bottle opening with tin foil paper, continuously stir in a 85℃ water bath for 5h, then cool in ice water, obtain a soybean protein isolate fiberization solution with a mass concentration of 4wt%.

[0079] S2, 1.5ml of plant essential oil (0.1-0.2ml of benzoic acid added in 1.5ml of tea tree essential oil) was added to the soybean protein isolate fiberized solution, and after homogenization at 12000rpm for 3min using a high-speed homogenization disperser, the protein fiber emulsion was obtained by degassing in an ultrasonic machine for 3min. 4g of polyvinyl alcohol and 1.2g of glycerol were measured and added to the above solution, and stirred uniformly to obtain a film-forming solution;

[0080] S3, 30mL of the film-forming solution was poured into a glass tank (10cm x 12cm) coated with a polytetrafluoroethylene film, and a layer of cling film with holes was covered on the surface of the glass tank to control the evaporation rate of the acid solvent, and dried at RH 40%, 25℃ for 24h to obtain a protein edible film.

[0081] As shown in Table 1, the effect of the addition ratio of polyvinyl alcohol on the properties of the edible film was investigated, and the results showed that the higher the concentration of polyvinyl alcohol, the higher the tensile strength and elongation at break of the edible film, and the lower the moisture permeability and solubility of the film.

[0082] Example 6

[0083] Effect of the addition ratio of glycerol on the properties of the edible film

[0084] A method for preparing a high-performance soy protein emulsion film, comprising the following steps:

[0085] S1, 4g of soybean protein isolate powder was accurately weighed and dispersed in 100g of a 40% by volume acetic acid-water solution, the bottle opening was sealed with tin foil paper, and continuously stirred in a 85℃ water bath for 5h, then cooled in ice water to obtain a soybean protein isolate fiberized solution with a mass concentration of 4wt%;

[0086] S2, 1.5ml of plant essential oil was added to the soybean protein isolate fiberized solution, and after homogenization at 12000rpm for 3min using a high-speed homogenization disperser, the protein fiber emulsion was obtained by degassing in an ultrasonic machine for 3min. 4g of polyvinyl alcohol and 2.8g of glycerol were measured and added to the above solution, and stirred uniformly to obtain a film-forming solution;

[0087] S3, 30mL of the film-forming solution was poured into a glass tank (10cm x 12cm) coated with a polytetrafluoroethylene film, and a layer of cling film with holes was covered on the surface of the glass tank to control the evaporation rate of the acid solvent, and dried at RH 40%, 25℃ for 24h to obtain a protein edible film.

[0088] As shown in Table 1, the effect of the addition ratio of glycerol on the properties of the edible film was investigated, and the results showed that the addition of glycerol reduced the tensile strength and elongation at break of the edible film, and increased the moisture permeability.

[0089] Example 7

[0090] A preparation method of a high-performance soy protein emulsion film, comprising the following steps:

[0091] S1, accurately take 4g of soybean protein isolate powder, disperse it in 100g of a 40% volume ratio acetic acid-water solution, seal the bottle opening with tin foil paper, continuously stir in a 85℃ water bath for 5h, then cool in ice water, obtain a 4wt% mass concentration of soybean protein isolate fibrosis solution;

[0092] S2, add 1.5ml of plant essential oil (0.1-0.2ml of lauric acid is added to 1.5ml of tea tree essential oil) to the soybean protein isolate fibrosis solution, use a high-speed homogenizing disperser to homogenize at a speed of 12000rpm for 3min, then place it in an ultrasonic machine for 3min to obtain a protein fiber emulsion, measure 4g of polyvinyl alcohol and 2g of glycerol and add them to the above solution, stir evenly to obtain a film-forming solution;

[0093] S3, take 30mL of the film-forming solution and pour it into a glass tank (10cm×12cm) coated with a polytetrafluoroethylene film, cover the surface of the glass tank with a preservative film with a number of holes to control the evaporation rate of the acid solvent, dry at RH40%, 25℃ for 24h to obtain a protein edible film.

[0094] As Figure 5 shown, the appearance of the protein emulsion edible film is uniform and transparent.

[0095] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement methods, all of which are included in the protection scope of the present application.

[0096] Comparative Example 1

[0097] The preparation method refers to Example 1, and the whole step does not involve acid heat treatment.

[0098] A preparation method of a high-performance soy protein emulsion film, comprising the following steps:

[0099] S1, accurately take 4g of soybean protein isolate powder, disperse it in 100g of a 40% volume ratio acetic acid-water solution, seal the bottle opening with tin foil paper, continuously stir in a 85℃ water bath for 5h, then cool in ice water, obtain a 4wt% mass concentration of soybean protein isolate fibrosis solution;

[0100] S2, 1.5 ml of plant essential oil was added to the soybean protein isolate fiberization solution, and after homogenization at 12000 rpm for 3 min using a high-speed homogenization disperser, the protein fiber emulsion was obtained by degassing in an ultrasonic machine for 3 min. 2 g of polyvinyl alcohol and 0.6 g of glycerol were measured and added to the above solution, and stirred uniformly to obtain a film-forming solution;

[0101] S3, 30 mL of the film-forming solution was poured into a glass tank (10 cm x 12 cm) coated with a polytetrafluoroethylene film, and a layer of preservative film with a plurality of holes was covered on the surface of the glass tank to control the evaporation rate of the acid solvent, and dried at RH 40%, 25°C for 24 h to obtain a protein edible film.

[0102] Comparative Example 2

[0103] The preparation method refers to Example 2, and the whole step does not involve acid heat treatment.

[0104] A preparation method of a high-performance soy protein emulsion film, comprising the following steps:

[0105] S1, accurately measure 2 g of soybean 11S protein powder, disperse it in 100 g of deionized water solution, stir at room temperature for 3 h, and obtain a soybean protein isolate solution with a mass concentration of 2 wt%;

[0106] S2, 1.5 ml of plant essential oil was added to the soybean protein isolate fiberization solution, and after homogenization at 12000 rpm for 3 min using a high-speed homogenization disperser, the protein fiber emulsion was obtained by degassing in an ultrasonic machine for 3 min. 2 g of polyvinyl alcohol and 0.6 g of glycerol were measured and added to the above solution, and stirred uniformly to obtain a film-forming solution;

[0107] S3, 30 mL of the film-forming solution was poured into a glass tank (10 cm x 12 cm) coated with a polytetrafluoroethylene film, and a layer of preservative film with a plurality of holes was covered on the surface of the glass tank to control the evaporation rate of the acid solvent, and dried at RH 40%, 25°C for 24 h to obtain a protein edible film.

[0108] Comparative Example 3

[0109] The preparation method refers to Example 3, and the whole step does not involve acid heat treatment, and a soybean protein isolate film is prepared.

[0110] A preparation method of a high-performance soy protein emulsion film, comprising the following steps:

[0111] S1, accurately measure 2 g of soybean 11S protein powder, disperse it in 100 g of deionized water solution, stir at room temperature for 3 h, and obtain a soybean protein isolate solution with a mass concentration of 2 wt%;

[0112] S2, 1.5 ml of plant essential oil was added to the soybean protein isolate fiberization solution, and after homogenization at 12000 rpm for 3 min using a high-speed homogenization disperser, the protein fiber emulsion was obtained by degassing in an ultrasonic machine for 3 min. 2 g of polyvinyl alcohol and 0.6 g of glycerol were measured and added to the above solution, and stirred uniformly to obtain a film-forming solution;

[0113] S3, 30 mL of the film-forming solution was poured into a glass tank (10 cm x 12 cm) coated with a polytetrafluoroethylene film, and a fresh-keeping film with a number of holes was covered on the surface of the glass tank to control the evaporation rate of the acid solvent. The protein edible film was obtained by drying at RH 40%, 25℃ for 24 h.

[0114] As shown in Figure 3 Fig. A1 and A2 are respectively the plan view and cross-sectional view of the prepared emulsion edible film when the mass concentration of natural soybean protein isolate (without acid heat treatment) is 4wt%, and the volume fraction of acetic acid is 40% (v / v); Fig. B1-B2 are respectively the plan view and cross-sectional view of the prepared emulsion edible film when the mass concentration of soybean protein isolate amyloid fiber is 4wt%, and the volume fraction of acetic acid is 40% (v / v), as shown in Table 1. Table 1 Comparison results of film properties of protein emulsion edible films prepared in Examples 1-7 and Comparative Examples 1-3 of the present application

[0115]

[0116] Although the embodiments of the present application are disclosed for illustrative purposes, those skilled in the art can understand that various alternatives, changes and modifications are possible without departing from the spirit and scope of the present application and the appended claims, therefore, the scope of the present application is not limited to the disclosed content of the embodiments.

Claims

1. A method for preparing a high-performance soybean protein emulsion film, characterized in that: The steps include: S1. Add 2-4 wt% soy protein isolate powder to an acetic acid-water binary mixed solvent with a pH of 2.0-3.0, stir and dissolve to obtain an acidified protein solution; S2. The protein solution prepared in step S1 is encapsulated in a sealed glass container, and the container is placed in a constant temperature water bath and heated at 65° C. to 95° C. for 1 to 6 hours. After the heating, the solution is cooled to obtain a soy protein isolate fiberization solution; S3, adding plant essential oil to the soy protein isolate fibrillation solution prepared in step S2, wherein the amount of plant essential oil added is 0.5-2.5wt%, and homogenizing at a speed of 12000 rpm using a high-speed homogenizer for 3 min, and then placing it in an ultrasonic machine for degassing for 3 min to obtain a protein fiber emulsion; S4, adding 2.0-6.0wt% polyvinyl alcohol and 10%-50% glycerol in a mass ratio of 1-5:0.1-3.5 to the protein fiber emulsion prepared in step S3, stirring evenly to prepare a membrane-forming solution; S5. Pour the film-forming liquid prepared in step S4 into a glass tank covered with a polytetrafluoroethylene film, cover the surface of the glass tank with a layer of plastic wrap pierced with several holes to control the evaporation rate of the acid solvent, and dry it at RH40% and 25°C for 24 hours to obtain a soybean protein edible film.

2. The method for preparing a high-performance soybean protein emulsion film according to claim 1, wherein: The protein in egg white powder is globular protein.

3. The method for preparing a high-performance soybean protein emulsion film according to claim 1, wherein: The volume fraction of acetic acid in the acetic acid-water binary mixed solvent is 30-50%.

4. The method for preparing a high-performance soybean protein emulsion film according to claim 1, wherein: The volume fraction of acetic acid in the acetic acid-water binary mixed solvent is 40%.

5. The method for preparing a high-performance soybean protein emulsion film according to claim 1, wherein: The plant essential oil is tea tree essential oil.

6. The method for preparing a high-performance soybean protein emulsion film according to claim 1, wherein: The method comprises adding lauric acid or benzoic acid to the plant essential oil.

7. The method for preparing a high-performance soybean protein emulsion film according to claim 6, characterized in that: The amount of lauric acid or benzoic acid added is 1-10 wt % of the plant essential oil.

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