A kind of multifunctional food preservative film and preparation method thereof

Abstract

The present invention provides a multifunctional food preservative film and a preparation method thereof, comprising the following steps: S1, preparing nano-lignin loaded with potassium sorbate; S2, taking a certain amount of chitosan and dissolving it in acidic deionized water to prepare a 1.5wt% solution M1; S3, mixing the solution M1 and the nano-lignin loaded with potassium sorbate in a certain proportion to prepare a film-forming liquid, pouring the film-forming liquid on a mold, and drying it naturally at room temperature to obtain a film, which is the multifunctional food preservative film. The present invention introduces nano-lignin loaded with potassium sorbate in the process of preparing the food preservative film, which not only enhances the thermal stability of the composite film, but also improves the antibacterial performance of the composite film, and can also effectively extend the shelf life of food.

Description

Technical Field

[0001] The invention relates to the technical field of food preservative films, and in particular to a multifunctional food preservative film and a preparation method thereof. Background Art

[0002] Most of the cling film sold on the market is made of ethylene masterbatch through polymerization reaction. According to the different types of ethylene masterbatch, cling film can be divided into three categories. The first is polyethylene, referred to as PE, which is mainly used for food packaging. The film used for fruits and vegetables we usually buy, including semi-finished products purchased from supermarkets, is made of this material; the second is polyvinyl chloride, referred to as PVC, which can also be used for food packaging, but it has a certain impact on human safety; the third is polyvinylidene chloride, referred to as PVDC, which is mainly used for the packaging of some cooked food, ham and other products.

[0003] Among these three types of cling film, PE and PVDC cling film are safe for human body and can be used without any worries. However, PE cling film has poor heat resistance and is not resistant to high temperature. It is easy to deform or even melt when heated, so it cannot be heated in microwave. PVC cling film contains carcinogens and is harmful to human body, so PVDC cling film is chosen. However, cling film itself cannot sterilize or inhibit bacteria, so even if cling film is used, it needs to be placed in the refrigerator.

[0004] Therefore, it is particularly important to develop a multifunctional food preservative film that is harmless to the human body, can withstand high temperatures, prolong the shelf life of food, and has a certain antibacterial effect. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a multifunctional food preservative film and a preparation method thereof, which has the characteristics of antibacterial and good heat resistance and can extend the shelf life of food to a certain extent.

[0006] The present invention is achieved in that:

[0007] The present invention provides a method for preparing a multifunctional food preservative film, comprising the following steps:

[0008] S1. preparing nano-lignin loaded with potassium sorbate;

[0009] S2, dissolving a certain amount of chitosan in acidic deionized water to prepare a 1.5 wt% solution M1;

[0010] S3, mixing the solution M1 and the nano-lignin loaded with potassium sorbate in a certain proportion and stirring to prepare a film-forming liquid, pouring the film-forming liquid on a mold, and drying it naturally at room temperature to obtain a film, which is the food preservative film.

[0011] Chitosan (CS) is widely used in food packaging due to its good antibacterial properties, biocompatibility and biodegradability. However, its application scope is limited by its shortcomings such as small specific surface area, high cost and poor thermal and mechanical properties.

[0012] Due to its excellent biocompatibility, biodegradability and antioxidant ability, LNP is often compounded with different bio-based materials to obtain composite materials with multiple functions.

[0013] Potassium sorbate (PS) is an antibacterial agent and preservative widely used in food, and is non-toxic and harmless to the human body, but it is easily oxidized and denatured by air when directly used and loses its antibacterial activity. Therefore, its application in various fields is limited. In order to prevent potassium sorbate from being oxidized by air, a loaded potassium sorbate lignin nanoparticle (PS-LNP) is prepared by a solvent-antisolvent self-assembly method using lignin as a carrier material. This not only improves the stability of potassium sorbate, but also makes it more widely used, and can also achieve the purpose of slow release to extend the antibacterial time and fresh-keeping.

[0014] Adding PS-LNP to CS can not only improve the thermal and mechanical properties of CS, but also give the CS film excellent UV shielding and antioxidant capabilities. In addition, the slow release of PS from LNP, the two double bonds of PS combined with the sulfhydryl groups in the microbial enzyme system in food can destroy the microbial enzyme system, inhibit microbial reproduction, achieve the purpose of antiseptic and antibacterial, and thus extend the shelf life of food.

[0015] Furthermore, the mass ratio of the solution M1 to the nano-lignin loaded with potassium sorbate is (97-99):(1-3).

[0016] Furthermore, the mass ratio of the solution M1 to the potassium sorbate-loaded nano-lignin was 97:3.

[0017] Furthermore, step S1 specifically includes the steps of:

[0018] S11, dissolving a certain amount of lignin in anhydrous ethanol, and performing ultrasonic dispersion to obtain a lignin-ethanol solution;

[0019] S12, dissolving a certain amount of potassium sorbate in deionized water, and ultrasonically dispersing to obtain a potassium sorbate solution;

[0020] S13, adding potassium sorbate solution dropwise to the lignin-ethanol solution to obtain a suspension;

[0021] S14, dialyzing the suspension, and freeze-drying after the dialysis to obtain nano-lignin loaded with potassium sorbate.

[0022] Furthermore, the mass ratio of lignin to potassium sorbate is 1:(0.5-3).

[0023] Furthermore, in step S13, the dropping speed of the potassium sorbate solution is 2 mL / min.

[0024] Furthermore, in step S14, the dialysis process is: transferring the suspension into a dialysis bag, placing it in excess deionized water for 48 hours, and regularly replacing the deionized water to remove residual ethanol and free potassium sorbate.

[0025] Furthermore, the mold is a polytetrafluoroethylene mold, which is naturally dried for 72 hours after casting.

[0026] The invention also provides a multifunctional food preservative film prepared by the preparation method.

[0027] The present invention has the following beneficial effects:

[0028] The invention introduces nano-lignin loaded with potassium sorbate in the process of preparing food preservative film, which not only enhances the thermal stability of the composite film, but also improves the antibacterial property of the composite film, and can also effectively prolong the shelf life of food. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 This is a diagram showing the regional inhibition effect of the cling film prepared in the comparative example and embodiments 1 to 6 of the present invention on Escherichia coli;

[0031] Figure 2 It is a test curve diagram of thermal stability of the cling film prepared in the comparative example and embodiments 1 to 6 of the present invention;

[0032] Figure 3 The figure is a curve diagram showing the effect of the fresh-keeping films prepared in the comparative example and embodiments 1 to 6 of the present invention on the weight loss rate of strawberries;

[0033] Figure 4 This is a bar graph of LOI test of the cling film prepared in the comparative example and embodiments 1 to 6 of the present invention. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1

[0036] The specific steps of the preparation method of the multifunctional food preservative film in this embodiment are as follows:

[0037] 1. Weigh 5 mg of lignin and dissolve it in 10 mL of anhydrous ethanol. Ultrasonic dispersion is performed for 30 min to obtain a lignin-ethanol solution.

[0038] 2. Dissolve 2.5 mg of potassium sorbate in 40 mL of deionized water and disperse by ultrasonic for 30 min to obtain a potassium sorbate solution;

[0039] 3. At room temperature, potassium sorbate solution was added dropwise to the lignin-ethanol solution using a peristaltic pump, and the dropping speed was controlled to be 2 mL / min to obtain a lignin nanosuspension loaded with potassium sorbate;

[0040] 4. After the addition is completed, continue stirring for 4 hours, transfer the suspension to a dialysis bag, place it in excess deionized water for 48 hours, regularly replace the deionized water to remove residual ethanol and free potassium sorbate, and freeze-dry to obtain potassium sorbate-loaded nano-lignin (PS-LNP), recorded as PS-0.5-LNP;

[0041] 5. Weigh a certain amount of chitosan (CS) and dissolve it in acidic deionized water to prepare a 1.5 wt% solution M1;

[0042] 6. Solution M1 and PS-0.5-LNP were mixed in a ratio of 99:1, stirred at 50 °C for 2 h to prepare a film-forming solution, poured onto a polytetrafluoroethylene mold with a diameter of 13.5 cm, and dried naturally at room temperature for 72 h to obtain a film, which was a food preservative film, recorded as CS-PS-0.5-LNP-1.

[0043] Example 2

[0044] The specific steps of the preparation method of the multifunctional food preservative film in this embodiment are as follows:

[0045] 1. Weigh 5 mg of lignin and dissolve it in 10 mL of anhydrous ethanol. Ultrasonic dispersion is performed for 30 min to obtain a lignin-ethanol solution.

[0046] 2. Dissolve 2.5 mg of potassium sorbate in 40 mL of deionized water and disperse by ultrasonic for 30 min to obtain a potassium sorbate solution;

[0047] 3. At room temperature, potassium sorbate solution was added dropwise to the lignin-ethanol solution using a peristaltic pump, and the dropping speed was controlled to be 2 mL / min to obtain a lignin nanosuspension loaded with potassium sorbate;

[0048] 4. After the addition is completed, continue stirring for 4 hours, transfer the suspension to a dialysis bag, place it in excess deionized water for 48 hours, regularly replace the deionized water to remove residual ethanol and free potassium sorbate, and freeze-dry to obtain potassium sorbate-loaded nano-lignin (PS-LNP), recorded as PS-0.5-LNP;

[0049] 5. Weigh a certain amount of chitosan (CS) and dissolve it in acidic deionized water to prepare a 1.5 wt% solution M1;

[0050] 6. Solution M1 and PS-0.5-LNP were mixed in a ratio of 97:3, stirred at 50 °C for 2 h to prepare a film-forming solution, poured onto a polytetrafluoroethylene mold with a diameter of 13.5 cm, and dried naturally at room temperature for 72 h to obtain a film, which was a food preservative film, recorded as CS-PS-0.5-LNP-3.

[0051] Example 3

[0052] The specific steps of the preparation method of the multifunctional food preservative film in this embodiment are as follows:

[0053] 1. Weigh 5 mg of lignin and dissolve it in 10 mL of anhydrous ethanol. Ultrasonic dispersion is performed for 30 min to obtain a lignin-ethanol solution.

[0054] 2. Dissolve 5 mg of potassium sorbate in 40 mL of deionized water and disperse by ultrasonic for 30 min to obtain a potassium sorbate solution;

[0055] 3. At room temperature, potassium sorbate solution was added dropwise to the lignin-ethanol solution using a peristaltic pump, and the dropping speed was controlled to be 2 mL / min to obtain a lignin nanosuspension loaded with potassium sorbate;

[0056] 4. After the addition is completed, stirring is continued for 4 h, and the suspension is transferred to a dialysis bag and placed in excess deionized water for 48 h. The deionized water is replaced regularly to remove residual ethanol and free potassium sorbate, and freeze-dried to obtain nano-lignin loaded with potassium sorbate (PS-LNP), which is recorded as PS-1-LNP;

[0057] 5. Weigh a certain amount of chitosan (CS) and dissolve it in acidic deionized water to prepare a 1.5 wt% solution M1;

[0058] 6. Solution M1 and PS-0.5-LNP were mixed in a ratio of 99:1, stirred at 50 °C for 2 h to prepare a film-forming solution, poured onto a polytetrafluoroethylene mold with a diameter of 13.5 cm, and dried naturally at room temperature for 72 h to obtain a film, which is a food preservative film, recorded as CS-PS-1-LNP-1.

[0059] Example 4

[0060] The specific steps of the preparation method of the multifunctional food preservative film in this embodiment are as follows:

[0061] 1. Weigh 5 mg of lignin and dissolve it in 10 mL of anhydrous ethanol. Ultrasonic dispersion is performed for 30 min to obtain a lignin-ethanol solution.

[0062] 2. Dissolve 5 mg of potassium sorbate in 40 mL of deionized water and disperse by ultrasonic for 30 min to obtain a potassium sorbate solution;

[0063] 3. At room temperature, potassium sorbate solution was added dropwise to the lignin-ethanol solution using a peristaltic pump, and the dropping speed was controlled to be 2 mL / min to obtain a lignin nanosuspension loaded with potassium sorbate;

[0064] 4. After the addition is completed, stirring is continued for 4 h, and the suspension is transferred to a dialysis bag and placed in excess deionized water for 48 h. The deionized water is replaced regularly to remove residual ethanol and free potassium sorbate, and freeze-dried to obtain nano-lignin loaded with potassium sorbate (PS-LNP), which is recorded as PS-1-LNP;

[0065] 5. Weigh a certain amount of chitosan (CS) and dissolve it in acidic deionized water to prepare a 1.5 wt% solution M1;

[0066] 6. Solution M1 and PS-0.5-LNP were mixed in a ratio of 97:3, stirred at 50 °C for 2 h to prepare a film-forming solution, poured onto a polytetrafluoroethylene mold with a diameter of 13.5 cm, and dried naturally at room temperature for 72 h to obtain a film, which was a food preservative film, recorded as CS-PS-1-LNP-3.

[0067] Example 5

[0068] The specific steps of the preparation method of the multifunctional food preservative film in this embodiment are as follows:

[0069] 1. Weigh 5 mg of lignin and dissolve it in 10 mL of anhydrous ethanol. Ultrasonic dispersion is performed for 30 min to obtain a lignin-ethanol solution.

[0070] 2. Dissolve 15 mg of potassium sorbate in 40 mL of deionized water and disperse by ultrasonic for 30 min to obtain a potassium sorbate solution;

[0071] 3. At room temperature, potassium sorbate solution was added dropwise to the lignin-ethanol solution using a peristaltic pump, and the dropping speed was controlled to be 2 mL / min to obtain a lignin nanosuspension loaded with potassium sorbate;

[0072] 4. After the addition is complete, continue stirring for 4 h, transfer the suspension to a dialysis bag, place it in excess deionized water for 48 h, regularly replace the deionized water to remove residual ethanol and free potassium sorbate, and freeze-dry to obtain potassium sorbate-loaded nano-lignin (PS-LNP), recorded as PS-3-LNP;

[0073] 5. Weigh a certain amount of chitosan (CS) and dissolve it in acidic deionized water to prepare a 1.5 wt% solution M1;

[0074] 6. Solution M1 and PS-0.5-LNP were mixed in a ratio of 99:1, stirred at 50 °C for 2 h to prepare a film-forming solution, poured onto a polytetrafluoroethylene mold with a diameter of 13.5 cm, and dried naturally at room temperature for 72 h to obtain a film, which was a food preservative film, recorded as CS-PS-3-LNP-1.

[0075] Example 6

[0076] The specific steps of the preparation method of the multifunctional food preservative film in this embodiment are as follows:

[0077] 1. Weigh 5 mg of lignin and dissolve it in 10 mL of anhydrous ethanol. Ultrasonic dispersion is performed for 30 min to obtain a lignin-ethanol solution.

[0078] 2. Dissolve 15 mg of potassium sorbate in 40 mL of deionized water and disperse by ultrasonic for 30 min to obtain a potassium sorbate solution;

[0079] 3. At room temperature, potassium sorbate solution was added dropwise to the lignin-ethanol solution using a peristaltic pump, and the dropping speed was controlled to be 2 mL / min to obtain a lignin nanosuspension loaded with potassium sorbate;

[0080] 4. After the addition is complete, continue stirring for 4 h, transfer the suspension to a dialysis bag, place it in excess deionized water for 48 h, regularly replace the deionized water to remove residual ethanol and free potassium sorbate, and freeze-dry to obtain potassium sorbate-loaded nano-lignin (PS-LNP), recorded as PS-3-LNP;

[0081] 5. Weigh a certain amount of chitosan (CS) and dissolve it in acidic deionized water to prepare a 1.5 wt% solution M1;

[0082] 6. Solution M1 and PS-0.5-LNP were mixed in a ratio of 97:3, stirred at 50 °C for 2 h to prepare a film-forming solution, poured onto a polytetrafluoroethylene mold with a diameter of 13.5 cm, and dried naturally at room temperature for 72 h to obtain a film, which was a food preservative film, recorded as CS-PS-3-LNP-3.

[0083] Comparative Example

[0084] The difference compared with Examples 1 to 6 is that the nano-lignin loaded with potassium sorbate is not added to the film-forming solution, and the solution M1 is directly used to form a film to obtain a food preservative film, which is recorded as CS.

[0085] The following performance tests were performed on the food preservative films prepared in Examples 1 to 6 and the comparative examples:

[0086] Antibacterial test: Cut the film sample into 6×5cm 2 The blocks were placed in a centrifuge tube containing 30 mL of 0.1% peptone solution. The initial E. coli concentration was 10 6 CFU / mL. The centrifuge tube was incubated in an inverted shaker at 37°C and 100 rpm for 24 hours. 0.1 mL of bacterial suspension was continuously collected every 0, 3, 6, 9, 12, and 24 hours and diluted with 0.9% sterile saline. Then, 100 μL of the appropriate dilution was spread on plate count agar and the number of colonies was counted after incubation at 37°C for 24 hours. The regional inhibition diagram of E. coli is shown in Figure 2. Figure 1 As shown, from left to right are: CS, CS-PS-0.5-LNP-1, CS-PS-0.5-LNP-3, CS-PS-1-LNP-1, CS-PS-1-LNP-3, CS-PS-3-LNP-1, CS-PS-3-LNP-3. It can be seen that adding PS-LNP to CS can effectively inhibit the growth of Escherichia coli and achieve the purpose of preservation and antibacterial, thereby extending the shelf life of food. CS-PS-3-LNP-1 and CS-PS-3-LNP-3 have better effects.

[0087] Thermal stability test: Seiko Exstar 6300 thermogravimetric analyzer was used to perform TGA test on the prepared film. The sample to be tested (4-6 mg) was placed in an oxidized crucible and heated from 30°C to 800°C at a heating rate of 10°C / min, with 99 ml / min of high-purity nitrogen flowing as the protective atmosphere. The results are shown in Figure 2. Figure 2 As shown, it can be seen that adding PS-LNP to CS can better improve the thermal properties of CS.

[0088] Freshness test: Strawberries without lesions and mechanical damage were selected as experimental objects. After washing the strawberries with deionized water, they were completely immersed in the CS-PS-LNP composite solution for 1 minute, taken out, dried, and placed at room temperature. The weight of the strawberries was weighed regularly every day to determine the weight loss. The results are as follows Figure 3 As shown, the weight loss rate of strawberries decreased when the food preservative film prepared in this embodiment was used. When CS-PS-3-LNP-3 was used, the weight loss rate of strawberries was less than 20% after 8 days.

[0089] Limiting oxygen index test: Cut the film into 10*100mm strips and measure the LOI value when it is burned for 50mm under a limiting oxygen index meter to determine its limiting oxygen index. Figure 4 As shown, the limiting oxygen index of the food preservative film prepared in this embodiment is significantly improved.

[0090] In summary, the present invention introduces nano-lignin loaded with potassium sorbate in the process of preparing food cling film, adds PS-LNP to CS, improves the thermal and mechanical properties of CS, and gives the CS film excellent ultraviolet shielding ability and antioxidant ability, making its application more extensive, and the slow release of PS from LNP, the two double bonds of PS combine with the sulfhydryl groups in the microbial enzyme system in the food, can destroy the microbial enzyme system, inhibit the reproduction of microorganisms, achieve the purpose of antiseptic and antibacterial, thereby extending the shelf life of food. The food cling film prepared by the present invention has the characteristics of antibacterial and good heat resistance, and can extend the shelf life of food to a certain extent.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a multifunctional food preservative film, It is characterized in that The following steps are involved: S1. preparing nano-lignin loaded with potassium sorbate; S2, dissolving a certain amount of chitosan in acidic deionized water to prepare a 1.5 wt% solution M1; S3, mixing the solution M1 and the nano-lignin loaded with potassium sorbate in a certain proportion and stirring to form a film-forming liquid, pouring the film-forming liquid on a mold, and drying it naturally at room temperature to obtain a film, which is the food preservative film; Wherein, step S1 specifically includes the steps of: S11, dissolving a certain amount of lignin in anhydrous ethanol, and performing ultrasonic dispersion to obtain a lignin-ethanol solution; S12, dissolving a certain amount of potassium sorbate in deionized water, and ultrasonically dispersing to obtain a potassium sorbate solution; S13, adding potassium sorbate solution dropwise to the lignin-ethanol solution to obtain a suspension; S14, dialyzing the suspension, and freeze-drying after the dialysis to obtain nano-lignin loaded with potassium sorbate.

2. The method for preparing the multifunctional food preservative film according to claim 1, Features: The mass ratio of solution M1 to nano-lignin loaded with potassium sorbate is (97-99):(1-3).

3. The method for preparing the multifunctional food preservative film according to claim 2, Features: The mass ratio of solution M1 and nano-lignin loaded with potassium sorbate was 97:

3.

4. The method for preparing the multifunctional food preservative film according to claim 1, Features: The mass ratio of lignin to potassium sorbate is 1:(1-3).

5. The method for preparing the multifunctional food preservative film according to claim 1, Features: In step S13, the dropping speed of the potassium sorbate solution is 2 mL / min.

6. The method for preparing the multifunctional food preservative film according to claim 1, Features: In step S14, the dialysis process is: transferring the suspension into a dialysis bag, placing it in excess deionized water for 48 hours, and regularly replacing the deionized water to remove residual ethanol and free potassium sorbate.

7. The method for preparing the multifunctional food preservative film according to claim 1, Features: The mold is a polytetrafluoroethylene mold, which is naturally dried for 72 hours after casting.

8. A multifunctional food preservative film, Features: The multifunctional food preservative film is prepared by the preparation method of any one of claims 1 to 7.

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