Edible seasoning packaging film based on soybean protein isolate and preparation method of edible seasoning packaging film

Abstract

The invention discloses an edible seasoning packaging film based on soybean protein isolate and a preparation method of the edible seasoning packaging film. The edible seasoning packaging film is prepared from the following components in percentage by weight: 5-7wt% of soybean protein isolate, 2-3wt% of glycerol and the balance of water. The preparation method comprises the following steps: adding the soybean protein isolate and the glycerol into the water, mixing, homogenizing, stirring the mixed solution, casting, molding, and drying, thereby obtaining the product. According to the edible seasoning bag, the soybean protein isolate is used as the raw material for preparing the edible seasoning bag for the first time, the packaging film with excellent mechanical property and barrier property is obtained through an optimized treatment process, and the packaging film has edibility, degradability, oxygen barrier property and good use stability and can be directly cooked together with food for eating; wide market application prospects are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of food packaging, and in particular relates to an edible seasoning packaging film based on soybean protein isolate and a preparation method thereof. Background Art

[0003] As a high-quality source of plant protein, soy protein isolate (SPI) has high nutritional value and renewability. Soy protein is currently the main product type of plant protein, accounting for more than half of the market value of plant protein. Soy protein isolate is the most commonly used soy protein product on the market, with high nutritional value and processing characteristics. At present, the amount of soybeans used for soy protein production in China is increasing year by year. In 2019, my country's soybean production was about 18.1 million tons, of which about 2.4 million tons were used for soy protein processing. By 2024, the amount of soybeans used for soy protein production and processing in my country will reach 3.7304 million tons. Protein-based food packaging materials not only have excellent physical properties, but also have biodegradability, can be rapidly degraded in the natural environment, and are pollution-free to the environment. Secondly, protein-based food packaging materials also have excellent oxygen barrier properties, which can effectively block oxygen penetration and extend the shelf life of food. Its protein film material shows good mechanical properties, oxygen barrier properties and biodegradability in the packaging field. In addition, soy protein isolate packaging bags are obtained from renewable resources and are regarded as a sustainable alternative to traditional synthetic plastics. The invention aims to develop a tear-free and edible seasoning packaging bag by using soy protein isolate film, so as to provide a healthy and environmentally friendly packaging solution for the food industry. Summary of the invention

[0004] One of the purposes of the present invention is to provide an edible seasoning packaging film based on soy protein isolate, which is made of soy protein isolate, glycerol and water, wherein the amount of the soy protein isolate is 5-7wt.%, and the amount of the glycerol is 2-3wt.%. Preferably, the amount of the soy protein isolate is 6wt.%, and the amount of glycerol is 2.5wt.%.

[0005] As a preferred embodiment of the method of the present invention, the soy protein isolate is prepared by the following steps:

[0006] Step 1, crushing soybeans, then adding n-hexane to the soybean powder for defatting, the solid-liquid ratio of soybean powder to n-hexane is 1:3, after discarding the supernatant, the remaining mixture is filtered, and n-hexane is added again for defatting until the liquid obtained by filtration is clear and transparent, and the defatted soybean powder is dried for later use;

[0007] Step 2, mixing the dried defatted soy powder in step 1 with deionized water at a solid-liquid ratio of 1:10, adjusting the pH value to 8.0, stirring and mixing, centrifuging, collecting the supernatant and adjusting the pH value to 4.5, centrifuging again, dissolving the protein precipitate in deionized water, adjusting the pH value to 7.5, and then dialyzing the protein solution, and freeze-drying the protein solution after dialysis to obtain the soy protein isolate.

[0008] Furthermore, in step 2, the pH is adjusted using 1 mol / L sodium hydroxide solution and 1 mol / L hydrochloric acid solution.

[0009] In a specific embodiment of the present invention, the preparation process of the soy protein isolate (SPI) is as follows: first, an appropriate amount of soybeans is placed in a high-speed multifunctional pulverizer, and then a small amount of liquid nitrogen is added to prevent the temperature from being too high during the pulverization process, resulting in protein denaturation. After about 30 seconds of pulverization, liquid nitrogen is added again, and the above operation is repeated 3 times; the obtained soybean powder is mixed with n-hexane at a solid-liquid ratio of 1:3 for defatting, and the mixture is stirred for 30 minutes with a precision power-enhancing electric stirrer and then allowed to stand for 1 hour. After the supernatant is poured out, the remaining mixture is filtered, and the n-hexane reagent is removed. The obtained soybean solids are mixed with n-hexane at a solid-liquid ratio of 1:3 and continue to defatting until the n-hexane reagent obtained by filtration is clear and transparent. The defatted soybean powder is spread in a fume hood and dried naturally for 48 hours, and then sealed in a ziplock bag and stored at -18°C for standby use. Take an appropriate amount of defatted soybean powder and deionized water at a solid-liquid ratio of 1:10, mix them with a glass rod, adjust the pH value to 8.0 with a 1mol / L sodium hydroxide solution, then stir with an electric stirrer at room temperature for 2 hours and centrifuge (7000rpm, 20 minutes), collect the supernatant and adjust the pH value to 4.5 with a 1mol / L hydrochloric acid solution, centrifuge again (7000rpm, 10 minutes) and redissolve the protein precipitate in deionized water, adjust the pH value to 7.5 with a 1mol / L sodium hydroxide solution, and then put the protein solution into a dialysis bag and dialyze it at 4°C for 48 hours. The dialysate is deionized water, and the dialysis external solution is replaced every 6 hours. After the dialysis is completed, the protein solution is freeze-dried to obtain soy protein isolate, and sealed at -18°C for standby use.

[0010] The soy protein isolate used in the present invention has a protein content of 90.43±1.13% as measured by the micro-Kjeldahl nitrogen determination method. Its superior amino acid composition and good mechanical properties can effectively enhance the structural stability and functionality of the film during the film-forming process, thereby improving the comprehensive performance of the film.

[0011] The glycerol is a food-grade product, and its main function is to act as a plasticizer. The addition of glycerol can not only improve the processability, flexibility and ductility of the film, but also improve the barrier properties of the film, so that the protein packaging film can meet multiple application scenarios.

[0012] The second object of the present invention is to provide a method for preparing the above-mentioned edible seasoning packaging film, wherein soy protein isolate and glycerin are added to water, mixed and homogenized, and then the mixed solution is stirred, cast and then dried to obtain a packaging film.

[0013] As a preferred embodiment of the method of the present invention, the mixed solution is homogenized at 10,000 rpm, and after homogenization, it needs to be fully stirred at 80°C to ensure that the protein and glycerol are fully mixed to form a uniform film-forming solution. This step helps the uniformity and stability of the film and ensures that the physical and chemical properties of the film after drying are not affected.

[0014] As a preferred embodiment of the method of the present invention, the thickness of the film is controlled at 0.15 mm, and the uniformity of the thickness directly affects the mechanical properties and barrier properties of the film. By strictly controlling the thickness of the film, not only can its stability be ensured, but it can also meet the application of multiple scenarios in practice.

[0015] As a preferred embodiment of the method of the present invention, the film drying temperature is controlled at 45°C and the drying time is 20 hours to ensure that the film is uniformly and completely dried. Appropriate drying conditions are conducive to forming a film with good performance.

[0016] The packaging film of the present invention improves its flexibility and mechanical properties by adding glycerol as a plasticizer, and optimizes the film thickness in structural design to meet the requirements of the seasoning package such as oil resistance, water resistance and edibility. The packaging film can be cooked together with instant food to improve the convenience of use, release the seasoning during the dissolution process, and increase the protein content of the instant food, improve its nutritional value, and reduce resource waste and environmental burden.

[0017] The packaging film of the present invention not only has excellent mechanical strength and good barrier properties, but also exhibits excellent biocompatibility and environmental protection. It is suitable for food packaging and other fields, can effectively reduce plastic pollution, and meets the requirements of sustainable development.

[0018] Beneficial effects: The present invention uses soy protein isolate as a raw material to prepare an edible seasoning packet for the first time. After an optimized processing process, a packaging film with excellent mechanical and barrier properties is obtained. The packaging film is edible, degradable, oxygen barrier and has good stability in use, and can be directly cooked and eaten with food. The implementation of this technical solution obtains an edible packaging film with excellent performance, which meets the urgent demand for high-performance film materials in the field of modern food packaging and has broad market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the finished product of instant noodle seasoning bag made of edible seasoning packaging film.

[0020] Figure 2This is a diagram of the light transmittance of edible seasoning packaging film.

[0021] Figure 3 The oil barrier test results of edible seasoning packaging film.

[0022] Figure 4 This is the thermal stability curve of edible seasoning packaging film. DETAILED DESCRIPTION

[0023] The preferred embodiments of the present invention will be described in detail below in conjunction with examples. It should be understood that the following examples are provided only for the purpose of illustration and are not intended to limit the scope of the present invention. Those skilled in the art may make various modifications and substitutions to the present invention without departing from the purpose and spirit of the present invention.

[0024] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0025] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0026] In the following embodiment, the preparation process of the soy protein isolate (SPI) is as follows: first, an appropriate amount of soybeans is placed in a high-speed multifunctional pulverizer, and then a small amount of liquid nitrogen is added to prevent the temperature from being too high during the pulverization process, resulting in protein denaturation. After about 30 seconds of pulverization, liquid nitrogen is added again, and the above operation is repeated 3 times; the obtained soybean powder is mixed with n-hexane at a solid-liquid ratio of 1:3 for defatting, and the mixture is stirred for 30 minutes with a precision power-enhancing electric stirrer and then allowed to stand for 1 hour. After the supernatant is poured out, the remaining mixture is filtered, and the n-hexane reagent is removed. The obtained soybean solids are mixed with n-hexane at a solid-liquid ratio of 1:3 and continue to defatting until the n-hexane reagent obtained by suction filtration is clear and transparent. The defatted soybean powder is spread in a fume hood and dried naturally for 48 hours, and then sealed in a ziplock bag and stored at -18°C for standby use. Take an appropriate amount of defatted soybean powder and deionized water at a solid-liquid ratio of 1:10, mix them with a glass rod, adjust the pH value to 8.0 with a 1mol / L sodium hydroxide solution, then stir with an electric stirrer at room temperature for 2 hours and centrifuge (7000rpm, 20 minutes), collect the supernatant and adjust the pH value to 4.5 with a 1mol / L hydrochloric acid solution, centrifuge again (7000rpm, 10 minutes) and redissolve the protein precipitate in deionized water, adjust the pH value to 7.5 with a 1mol / L sodium hydroxide solution, and then put the protein solution into a dialysis bag and dialyze it at 4°C for 48 hours. The dialysis external liquid is deionized water, and the dialysis external liquid is replaced every 6 hours. After the dialysis is completed, the protein solution is freeze-dried to obtain soy protein isolate, and sealed at -18°C for standby use.

[0027] Example 1

[0028] A preparation process of an edible seasoning packaging film based on soy protein isolate is as follows:

[0029] 1. Selection of raw materials

[0030] Soy protein isolate (SPI): protein content ≥ 90%;

[0031] Glycerin (food grade): As a plasticizer, it enhances the flexibility and ductility of the packaging film;

[0032] Deionized water (Wahaha): dissolves SPI and glycerol to ensure the uniformity of the film-forming solution.

[0033] 2. Process steps

[0034] Solution preparation: weigh 6 g SPI and 2.5 g glycerol, dissolve in 100 mL deionized water, and stir evenly;

[0035] Homogenization: Place the mixed solution in a high-speed disperser at a speed of 10,000 rpm for 3 minutes to ensure that the solution is free of lumps and evenly dispersed;

[0036] Heating and dissolving: Stir the homogenized solution continuously at 80°C for 30 minutes to ensure that SPI and glycerol are fully mixed;

[0037] Casting: Pour the heated homogenized solution into a clean plastic mold, making sure the liquid surface is flat;

[0038] Drying and film formation: The casted mold was placed in a 45°C drying oven for 20 hours, and then balanced in a constant temperature and humidity chamber for 48 hours (25°C, 50% RH) to obtain a uniform, transparent SPI film.

[0039] During the drying process, attention should be paid to uniform wind flow to avoid uneven film thickness or wrinkles; the film thickness should be controlled within the range of 0.15±0.02mm to ensure that the mechanical properties and air permeability of the film meet the requirements.

[0040] Afterwards, the prepared packaging film was tested, including nutritional indicators, optical properties, mechanical properties, barrier properties, thermal stability, microbial indicators, etc. The details are as follows:

[0041] 1. Nutritional indicators

[0042] The nutritional content of SPI film was determined using the corresponding national standard method. As shown in Table 1, SPI film contains eight essential amino acids for the human body, which is similar to meat, fish, eggs, and milk, and is a complete protein. In addition, it has an extremely low fat content and no cholesterol, making it a very pure protein supplement option.

[0043] Table 1. Nutritional composition of edible seasoning packaging film based on soy protein isolate

[0044]

[0045] 2. Optical properties

[0046] Color measurement: The appearance color of the SPI film was measured using a colorimeter, with a standard white plate (L*=99.9, a*=0.06, b*=4.88) as a reference, and the relevant parameters were L*=90.76, a*=-0.25, b*=6.33 and total color difference (ΔE)=9.61. Figure 1 As shown, the film exhibits a light yellow appearance with high transparency.

[0047] Transmittance: The transmittance of the SPI film was measured by a UV spectrophotometer. The results showed that the transmittance in the 200-300nm UV region was close to 0%. Figure 2 As shown, it shows that the film has good UV resistance; at the same time, the higher light transmittance in the visible light region ensures the transparency of the packaging film.

[0048] 3. Mechanical properties

[0049] The tensile strength and elongation at break of the film were tested using a physical property tester. The results showed that the tensile strength was 4.39±0.34MPa and the elongation at break was 32.23±0.88%, which can meet the processing and use requirements of seasoning packaging film.

[0050] 4. Barrier properties

[0051] Water vapor permeability: The water vapor permeability of the SPI film was measured at 25°C and 50% relative humidity using the classic cup method. The result was 7.35±0.24 (10 -10 g -1 s -1 m -1 ), has good moisture barrier properties.

[0052] Oxygen permeability: The mouth of the test bottle containing linoleic acid was sealed with a film and the oxygen permeability was measured. The result was 4.32±0.86 (10 -4 cc / mhatm), can effectively block oxygen and extend the shelf life of food.

[0053] Oil resistance test: Wrap the mouth of the test bottle containing edible oil with the SPI film, place it upside down on filter paper for 24 hours, and observe whether there is obvious oil penetration in the film. Figure 3 As shown, the results show that no oil is analyzed out of the filter paper, indicating that the packaging film has good oil barrier properties and is suitable for practical applications in seasoning packages.

[0054] 5. Thermal stability

[0055] TGA test: The thermal stability of the SPI film was analyzed using a thermogravimetric analyzer (TGA 550). Figure 4 As shown, within the temperature range of 30-800°C, the mass loss of the SPI film within 130°C is less than 2%, mainly due to water evaporation, ensuring its stability under daily transportation and storage conditions.

[0056] Heat sealing strength test: The heat sealing strength test result is 7.46±0.23N / 15mm, which meets the heat sealing strength requirements of ordinary grade food packaging films in the national standard.

[0057] 6. Microbiological indicators

[0058] Microbiological testing: With reference to national food safety standards, SPI film was tested for microorganisms. The results showed that mold and total colony counts met food safety standards, and common pathogenic bacteria such as Escherichia coli, Staphylococcus aureus and Salmonella were not detected, ensuring the food safety of the packaging film.

[0059] Example 2

[0060] The application of edible seasoning packaging film based on soy protein isolate can be used to make instant noodle seasoning packaging bags. When cooking instant noodles, users put the seasoning packet together with the noodles into boiling water without tearing the seasoning packaging bag. The SPI packaging film can be partially dissolved in hot water to release the seasoning. The undissolved seasoning packet can be eaten with instant noodles, with a smooth taste and a taste similar to bean curd. It can not only increase the protein content in instant food and improve its nutritional value, but also simplify the cooking process of instant food.

[0061] In summary, the present invention provides an edible seasoning packaging film based on soy protein isolate, which can effectively replace the traditional plastic seasoning packaging film by optimizing the raw material ratio and process conditions, has the advantages of environmental protection, convenience, nutrition, etc., and meets the current sustainable development needs of food packaging. The invention has good market application prospects and promotion value.

Claims

1. An edible seasoning packaging film prepared based on soy protein isolate, characterized in that: The invention is prepared from isolated soy protein, glycerol and water, wherein the amount of the isolated soy protein is 5-7 wt.%, and the amount of the glycerol is 2-3 wt.%.

2. The edible seasoning packaging film according to claim 1, characterized in that: The amount of soy protein isolate used is 6 wt.%, and the amount of glycerol used is 2.5 wt.%.

3. The edible seasoning packaging film according to claim 1, characterized in that: The soy protein isolate is prepared by the following steps: Step 1, crushing soybeans, then adding n-hexane to the soybean powder for defatting, the solid-liquid ratio of soybean powder to n-hexane is 1:3, after discarding the supernatant, the remaining mixture is filtered, and n-hexane is added again for defatting until the liquid obtained by filtration is clear and transparent, and the defatted soybean powder is dried for later use; Step 2, mixing the dried defatted soy powder in step 1 with deionized water at a solid-liquid ratio of 1:10, adjusting the pH value to 8.0, stirring and mixing, centrifuging, collecting the supernatant and adjusting the pH value to 4.5, centrifuging again, dissolving the protein precipitate in deionized water, adjusting the pH value to 7.5, and then dialyzing the protein solution, and freeze-drying the protein solution after dialysis to obtain the soy protein isolate.

4. The edible seasoning packaging film according to claim 3, characterized in that: In step 2, the pH is adjusted using 1 mol / L sodium hydroxide solution and 1 mol / L hydrochloric acid solution.

5. The method for preparing the edible seasoning packaging film according to any one of claims 1 to 4, characterized in that: Soy protein isolate and glycerin are added to water, mixed and homogenized, and then the mixed solution is stirred, cast and then dried to obtain a packaging film.

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