Method for preparing antibacterial and freshness-retaining packaging material for fruits by using 3D printing technology

Abstract

A method for preparing an antibacterial and freshness-retaining packaging material for fruits by using the 3D printing technology, relating to the field of food processing. The method comprises the st

Description

Method for preparing fruit antibacterial and fresh-keeping packaging materials using 3D printing technology Technical Field

[0001] The invention relates to a method for preparing a fruit antibacterial and fresh-keeping packaging material by utilizing 3D printing technology, and belongs to the field of novel food processing. Background Art

[0002] Fruit is an important component of the human diet and a significant source of vitamins, dietary fiber, and phytochemicals. Adequate fruit intake plays a crucial role in maintaining good health, boosting immunity, and reducing the risk of chronic diseases such as diabetes and hypertension. However, during storage and transportation, fruit can become spoiled and deteriorate due to mechanical damage from collisions and contamination from environmental microorganisms, damaging the flavor and taste of the fruit and reducing its inherent value. References have disclosed a collision-resistant, transparent, and fresh-keeping fruit bag. This packaging material utilizes a porous structure made of a material of a certain thickness to provide collision-resistant preservation. While this packaging material reduces mechanical damage to fruit during storage to a certain extent, the porous structure makes it susceptible to contamination from external microorganisms, resulting in a decrease in the fruit's freshness. References have also disclosed a collision-resistant, air-filled film bag specifically for peaches. This method reduces mechanical damage to fruit by filling a specific material with gas. However, the resulting packaging bag is complex and difficult to manufacture, resulting in high economic costs and a disadvantage for the long-term development of the enterprise. Furthermore, the packaging material used is non-degradable.

[0003] Probiotics are defined as live microorganisms that, when consumed in sufficient amounts, are beneficial to human health. For example, probiotics can relieve gastrointestinal discomfort and regulate intestinal function. Oral probiotics can also promote metabolism, reduce lipids and promote weight loss, and even benefit skin health. However, their application in food packaging is rarely reported.

[0004] Summary of the Invention

[0005] The present invention aims to address current shortcomings in fruit preservation and the vulnerability of fruit to damage during transportation. Based on this, a method is proposed using polysaccharides and PVC as materials, utilizing coaxial and uniaxial 3D printing technology. The shell layer is loaded with flame-retardant PVC material with a wide hardness range, while the core layer is encapsulated with antibacterial probiotics. This creates a core-shell product. Furthermore, a single-axis printing layer is used to enhance the protective capabilities of the outer layer. Ultimately, a 3D-printed packaging material is developed that preserves fruit on the inner layer and protects it on the outer layer.

[0006] The present invention achieves the above technical objectives through the following technical means:

[0007] A method for developing a 3D printed packaging material containing probiotics using PVC material and polysaccharide, the specific steps are as follows:

[0008] (1) Preparation of the nuclear layer solution: First, gum arabic is dissolved in deionized water to obtain a gum arabic solution; secondly, pullulan is dissolved in deionized water to obtain a pullulan solution; then, the probiotics are cultured, centrifuged, and resuspended to obtain a bacterial solution; finally, the bacterial solution is mixed with the gum arabic solution and the pullulan solution in a certain proportion, sealed, and stirred to dissolve, thereby obtaining the nuclear layer solution;

[0009] (2) Preparation of shell solution: polyvinyl chloride (PVC), modifier and plasticizer are mixed and stirred to obtain a shell solution;

[0010] (3) Preparation of packaging materials: using the shell layer solution and the core layer solution as 3D printing solutions, and using coaxial plus uniaxial 3D printing technology for printing;

[0011] First, the shell layer solution and the core layer solution prepared in step (1) are injected into the syringe respectively, and the shell layer solution is pushed at a faster rate than the core layer solution, and finally received on the bottom plate of the device to obtain a coaxial printed product of the core-shell structure;

[0012] Then, using single-axis 3D printing technology, only the shell solution is printed on the outer layer of the core-shell structure of the coaxially printed product, obtaining an antibacterial and fresh-keeping packaging material with an inner and outer double-layer structure; the inner layer keeps the fruit fresh, while the outer layer protects it.

[0013] Preferably, the mass concentration of the gum arabic solution in step (1) is 10% to 15%, and the mass concentration of the pullulan solution is 10% to 15%.

[0014] Preferably, the probiotics described in step (1) are any one of Lactobacillus acidophilus, Lactobacillus casei, Bifidobacterium thermophilus, and Lactobacillus bulgaricus; the specific conditions for culturing the probiotics are: inoculating in MRS liquid culture medium at an inoculation ratio of 1-2 g: 100 ml, culturing at a temperature of 35-37 ° C, and culturing for 10-12 h; the concentration of the bacterial solution is 10 9 ~10 10 1g (CFU / g).

[0015] Preferably, the gum arabic solution, pullulan solution and bacterial solution in step (1) are mixed in a mass ratio of 1:3-4:1-3.

[0016] Preferably, the modifier described in step (2) is any one of chlorinated polyethylene (CPE), acrylic copolymer (ACR), nitrile rubber (NBR) or silicon dioxide (SiO2); the plasticizer is any one of ethylene vinyl acetate rubber (EVM), diisodecyl adipate (DIDA), dioctyl azelate (DOZ), dibutyl sebacate (DBS), dioctyl sebacate (DOS) or dioctyl phthalate (DOP).

[0017] Preferably, the polyvinyl chloride (PVC), modifier and plasticizer in step (2) are mixed in a mass ratio of 100:5-10:20-30.

[0018] Preferably, the coaxial 3D printing technical condition parameters in step (3) are: the core layer nozzle diameter is 0.8-1.4 mm, and the shell layer nozzle diameter is 1.7-2.5 mm; the printing temperature selection is: the core layer printing temperature is 25-40°C, and the shell layer printing temperature is 30-60°C; the propulsion rate selection is: the core layer solution propulsion rate is 5-8 mm / s, and the shell layer solution propulsion rate is 15-40 mm / s, the ratio of the core layer solution propulsion rate to the shell layer solution rate is 1:(3-5), and the printing speed is 15-30 mm / s.

[0019] Preferably, the technical condition parameters of the uniaxial 3D printing described in step (3) are: nozzle diameter of 1.7 to 2.5 mm; printing temperature of 30 to 60° C.; and printing speed of 15 to 30 mm / s.

[0020] Beneficial effects of the present invention:

[0021] The present invention develops 3D-printed packaging materials containing probiotics using PVC materials and polysaccharides. Using coaxial technology, the probiotics are printed on the inner layer. On the one hand, the probiotics can produce antibacterial components such as extracellular polysaccharides to better preserve the fruit. On the other hand, the probiotics can have a positive impact on the host's health and prevent various diseases such as constipation and diarrhea. Therefore, these antibacterial components can be directly brought into contact with the preserved product, greatly enhancing the antibacterial effect while being harmless to the human body.

[0022] The so-called preservation is reflected in the probiotics in the core layer solution. Since probiotics contain a variety of bacteriocins, they can play an antibacterial role, thereby extending the shelf life of the fruit; the PVC material modified by this outer shell layer has an adjustable hardness, which can effectively resist mechanical damage to the fruit caused by the outside world. The two materials are printed into a shell similar to the shape of the fruit through coaxial 3D printing technology. Then, on the basis of the coaxial technology, a single-axis anti-collision layer is used to print a layer to protect the fruit, thereby playing a better role in preserving the fruit.

[0023] The present invention develops 3D-printed packaging materials containing probiotics using PVC materials and polysaccharides. By adjusting the ratio of PVC to modifiers and plasticizers in the shell solution, the printability and hardness adjustability of the shell are greatly improved, thereby effectively reducing damage to fruit caused by inevitable collisions during storage and transportation, thereby extending the fruit's shelf life. As the ratios of PVC, modifiers, and plasticizers vary, the tensile strength of the packaging material decreases while the elongation increases. This indicates that the ratio of PVC, modifiers, and plasticizers has a certain impact on the mechanical strength of the packaging material, with the most significant effect being achieved when the plasticizer ratio is between 20 and 30 and the modifier ratio is between 5 and 10.

[0024] The PVC material and polysaccharide designed by the present invention are used to develop 3D printing packaging materials containing probiotics. The main function of the 3D printing packaging materials for fruit preservation is that the probiotics in the inner layer can produce antibacterial active ingredients to slow down the spoilage of the fruit, and the modified PVC material in the outer layer can reduce unnecessary mechanical damage to the fruit during transportation. The combination of the two greatly improves the ability to preserve the fruit.

[0025] The packaging material designed by the present invention utilizes coaxial and uniaxial 3D printing technology, which not only achieves the function of preserving the inner layer but also plays a vital role in reducing mechanical damage to the fruit with the multi-thickness anti-collision layer on the outer layer. The designed packaging material is safe and non-toxic and can directly contact food. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of uniaxial (A) and coaxial (B) 3D printing devices.

[0027] Figure 2 shows the survival rate of probiotics in three solutions under different mixing ratios.

[0028] Figure 3 is a test graph of the tensile strength (A) and elongation at break (B) of packaging materials made in different ways by adding different proportions of polyvinyl chloride (PVC), modifiers and plasticizers. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical route and advantages of the present invention more clear, the present invention is further explained in detail in combination with the following specific implementation methods and with reference to certain drawings.

[0030] The specific cultivation process of probiotics liquid is as follows: the whole cultivation process is carried out under sterile conditions, 1g of bacterial powder is placed in 50ml of MRS liquid culture medium and cultured at 37℃ for 12h, then the liquid is centrifuged at 5000r for 5min and resuspended with physiological saline to obtain a final concentration of 10 9 1g (CFU / g) of probiotic resuspension.

[0031] Example 1:

[0032] A method for developing a 3D-printed packaging material containing probiotics using PVC material and polysaccharide, using coaxial plus uniaxial 3D printing technology, includes the following steps:

[0033] (1) Preparation of nuclear layer solution: First, gum arabic was dissolved in deionized water to obtain a 20% by mass gum arabic solution; then, pullulan was dissolved in deionized water to obtain a 20% by mass pullulan solution; then, a resuspension of Lactobacillus bulgaricus was added to the above mixture and stirred to obtain the nuclear layer solution; wherein the mass ratios of the gum arabic solution, pullulan solution, and bacterial solution were set to 1:4:1, 1:4:1.5, 1:4:2, and 1:4:2.5.

[0034] (2) Preparation of shell solution: PVC with a degree of polymerization of 1800, ethylene vinyl acetate rubber (EVM) as plasticizer, and chlorinated polyethylene (CPE) as modifier were selected. PVC, modifier, and plasticizer were mixed in a certain proportion and stirred evenly at a high temperature of 170°C to obtain a blend of the three materials, which was then cooled to 60°C to obtain the shell solution; the ratios of polyvinyl chloride (PVC), modifier, and plasticizer were set to 100:5:20, 100:6:22, 100:7:24, 100:8:25, 100:9:30, and 100:10:32.

[0035] (3) Preparation of packaging materials: Using coaxial plus uniaxial 3D printing technology, the shell layer and core layer solutions are injected into syringes respectively;

[0036] First, coaxial 3D printing was performed with the following parameters: the core layer nozzle diameter was 1.4 mm, and the shell layer nozzle diameter was 2.5 mm; the printing temperature selection was 37°C for the core layer and 60°C for the shell layer; and the printing speed was 25 mm / s for both.

[0037] Then, uniaxial 3D printing was performed using only the shell solution, with the following uniaxial parameters: nozzle diameter: 2.5 mm; printing temperature: 60°C; printing speed: 25 mm / s.

[0038] In order to better characterize the antibacterial ability of the above packaging materials, the survival rate of probiotics in the nuclear layer solution can be tested to characterize it.

[0039] Figure 2 shows the survival rate of probiotics under different mixing ratios of gum arabic solution, pullulan solution and bacterial solution, where the mass ratios of gum arabic solution, pullulan solution and bacterial solution corresponding to GA-PUL-LB(a), GA-PUL-LB(b), GA-PUL-LB(c) and GA-PUL-LB(d) are 1:4:1, 1:4:1.5, 1:4:2 and 1:4:2.5 respectively. As can be seen from Figure 2, the number of probiotics in GA-PUL-LB(a) in the initial state is 8.03±0.12 [lg(CFU / g)]; the number of probiotics in GA-PUL-LB(b) is 8.54±0.13 [lg(CFU / g)]; the number of probiotics in GA-PUL-LB(c) is 9.72±0.15 [lg(CFU / g)]; the number of probiotics in GA-PUL-LB(d) is 1:4:1, 1:4:1.5, 1:4:2 and 1:4:2.5 respectively. The number of probiotics in GA-PUL-LB (a) was 4.82±0.16[lg(CFU / g)] after 28 days of storage at room temperature; the number of probiotics in GA-PUL-LB (b) was 5.15±0.14[lg(CFU / g)]; the number of probiotics in GA-PUL-LB (c) was 6.28±0.18[lg(CFU / g)]; the probiotic count of GA-PUL-LB (d) was 6.75±0.14 [1g (CFU / g)]; compared with the initial colony count, the survival rate of GA-PUL-LB (a) was 60.02%; the survival rate of GA-PUL-LB (b) was 60.30%; the survival rate of GA-PUL-LB (c) was 64.61%; and the survival rate of GA-PUL-LB (d) was 66.50%. In summary, the proportions specified in the present invention all achieved good preservation effects; and the higher the initial probiotic content, the higher the content of surviving probiotics after 28 days. This also shows that probiotics with a high initial concentration have a better preservation effect.

[0040] Figure 3 shows the effects of adding different ratios of polyvinyl chloride (PVC), modifier, and plasticizer on the tensile strength (A) and elongation at break (B) of packaging materials produced by different methods. The horizontal axes 1, 2, 3, 4, 5, and 6 represent the ratios of polyvinyl chloride (PVC), modifier, and plasticizer in the shell solution of 100:5:20, 100:6:22, 100:7:24, 100:8:25, 100:9:30, and 100:10:32, respectively. Uniaxial, Coaxial, and Uniaxial-Coaxial represent uniaxial, coaxial, and coaxial plus uniaxial printing methods, respectively.

[0041] As shown in Figure 3, with the increase of modifier and plasticizer, the tensile strength of the packaging material decreases, while the elongation increases. This indicates that the changes in the content of polyvinyl chloride (PVC), modifier, and plasticizer have a significant impact on the mechanical strength of the packaging material. When the ratio of polyvinyl chloride (PVC), modifier, and plasticizer is 100:25:8 and 100:30:9, the tensile strength and elongation at break are both within the ratio that is easy to print and form. Under this ratio condition, the material can better exert its anti-collision function, indicating that this ratio condition is more conducive to fruit preservation.

[0042] Secondly, Figure 3 also shows that, when the ratio of polyvinyl chloride (PVC), modifier, and plasticizer remains unchanged, different printing methods (uniaxial, coaxial, and uniaxial plus coaxial) also have a very significant impact on the mechanical strength of the packaging material. Different printing methods directly affect the performance of the material; in particular, the coaxial plus uniaxial printing method has the greatest impact on the mechanical strength of the packaging material.

[0043] Note: The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Therefore, although this specification has described the present invention in detail with reference to the above embodiments, it should be understood by those skilled in the art that the present invention may still be modified or replaced by equivalents. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A method for preparing fruit antibacterial and fresh-keeping packaging materials using 3D printing technology, characterized in that: The following steps are involved: (1) Preparation of nuclear layer solution: First, dissolve gum arabic in deionized water to obtain a gum arabic solution with a mass concentration of 10% to 15%; secondly, dissolve pullulan in deionized water to obtain a pullulan solution with a mass concentration of 10% to 15%; then, inoculate and culture the probiotics, centrifuge and resuspend them to obtain a bacterial solution with a concentration of 10 9 ~10 10 lg (CFU / g); finally, the bacterial solution was mixed with the gum arabic solution and the pullulan solution in a mass ratio of 1:3-4:1-3, sealed, and stirred to dissolve to obtain a nuclear layer solution; (2) Preparation of shell solution: polyvinyl chloride, a modifier, and a plasticizer are mixed and stirred uniformly to obtain a shell solution; the polyvinyl chloride, the modifier, and the plasticizer are mixed in a mass ratio of 100:5-10:20-30; the modifier is chlorinated polyethylene; (3) Preparation of packaging materials: using the shell layer solution and the core layer solution as 3D printing solutions, and using coaxial plus uniaxial 3D printing technology for printing; First, the shell layer solution prepared in step (2) and the core layer solution prepared in step (1) are respectively injected into a syringe, and the shell layer solution is pushed at a faster rate than the core layer solution, and finally received on the bottom plate of the device to obtain a coaxial printed product with a core-shell structure; Then, using single-axis 3D printing technology, only the shell solution is printed on the outer layer of the core-shell structure of the coaxially printed product, obtaining an antibacterial and fresh-keeping packaging material with an inner and outer double-layer structure; the inner layer keeps the fruit fresh, while the outer layer protects it.

2. The method for preparing a fruit antibacterial and fresh-keeping packaging material using 3D printing technology according to claim 1, characterized in that: The probiotics described in step (1) are any one of Lactobacillus acidophilus, Lactobacillus casei, Bifidobacterium thermophilus, and Lactobacillus bulgaricus; the specific conditions for culturing the probiotics are: inoculating in MRS liquid culture medium at an inoculation ratio of 1-2 g:100 ml, culturing at a temperature of 35-37° C., and culturing for 10-12 h.

3. The method for preparing fruit antibacterial and fresh-keeping packaging materials using 3D printing technology according to claim 1, characterized in that: The coaxial 3D printing technical condition parameters described in step (3) are: nozzle diameter: the core layer nozzle diameter is 0.8-1.4 mm, and the shell layer nozzle diameter is 1.7-2.5 mm; printing temperature selection: the core layer printing temperature is 25-40°C, and the shell layer printing temperature is 30-60°C; propulsion rate selection: the core layer solution propulsion rate is 5-8 mm / s, and the shell layer solution propulsion rate is 15-40 mm / s. The ratio of the core layer solution propulsion rate to the shell layer solution propulsion rate is 1:(3-5), and the printing speed is 15-30 mm / s.

4. The method for preparing fruit antibacterial and fresh-keeping packaging materials using 3D printing technology according to claim 1, characterized in that: The technical parameters of the single-axis 3D printing described in step (3) are: nozzle diameter: 1.7-2.5 mm; printing temperature: 30-60° C.; printing speed: 15-30 mm / s.

5. The packaging material prepared according to any one of claims 1 to 4 is used for antibacterial and food preservation.