Preparation method and application of biomass carbon dot chitosan-based preservative film

Abstract

The invention discloses a preparation method and application of a biomass carbon dot chitosan-based preservative film. The preservative film is prepared by taking chitosan and tea polyphenol carbon dots as main raw materials and taking glycerol as a plasticizer as an auxiliary material through a solution casting method. The preparation method comprises the following specific steps: synthesizing tea polyphenol carbon dots through a hydrothermal method, dissolving chitosan in a 1% acetic acid aqueous solution, adding glycerol and the tea polyphenol carbon dots, uniformly stirring, ultrasonically defoaming, uniformly coating to form a film, and drying at 40 DEG C for 6 hours to obtain the preservative film. The preservative film has excellent antibacterial, antioxidant and moisturizing properties, can significantly prolong the preservation period of perishable food such as salmon, inhibit the growth of microorganisms and maintain the nutrition and taste of the food, is environment-friendly and degradable, and reduces the use of chemical preservatives. The preparation method is simple, low in cost, suitable for large-scale production and capable of being widely applied to fresh food packaging, and a green solution is provided for development of a food preservation technology.

Description

Technical Field

[0001] The invention relates to the technical field of food packaging, and in particular to the preparation and application of a biomass carbon dot chitosan-based fresh-keeping film. Background Art

[0002] Foodborne pathogens refer to microorganisms that can cause disease and are transmitted through contaminated food, posing a major threat to public health. Foodborne diseases not only have a direct impact on personal health, but also pose a challenge to public health. With the increasing severity of global environmental problems, the innovation of food preservation technology has become an important direction for improving food quality and extending the shelf life. Traditional food preservation methods, such as the use of chemical preservatives, can effectively inhibit the growth of microorganisms, but they pose potential hazards to human health and the environment. Therefore, the development of safe, environmentally friendly and efficient natural preservation materials has become an important research topic in the food field.

[0003] Biomass carbon dots are a type of nanomaterial made from biomass materials through a simple synthesis method. They have excellent biocompatibility, fluorescence properties and good antibacterial properties. These properties make biomass carbon dots have great application potential in food preservation and packaging materials.

[0004] Chitosan is a natural polymer material with good biodegradability, antibacterial properties and film-forming ability. Chitosan cling film is widely used in food packaging, which can not only extend the shelf life of food, but also reduce the water loss of food and maintain its taste and nutritional content.

[0005] Combining the advantages of biomass carbon dots and chitosan, the biomass carbon dots-chitosan composite cling film can further improve its antioxidant, antibacterial and moisturizing properties, especially in the preservation of perishable foods such as salmon. By rationally designing the structure and function of the composite film, the shelf life of salmon can be effectively extended, the phenomenon of corruption and deterioration can be reduced, and its safety and market competitiveness can be improved.

[0006] Therefore, this patent proposes a chitosan cling film with biomass carbon dots, aiming to provide a natural, environmentally friendly and efficient preservation solution for perishable foods such as salmon. Summary of the invention

[0007] In order to solve the above problems, the present invention provides a composite fresh-keeping film with biomass carbon dots and chitosan as main components.

[0008] The cling film is prepared from the following components in proportion:

[0009] (1) Chitosan: provides good film-forming ability, biodegradability and antibacterial properties;

[0010] (2) Tea polyphenol carbon dots: as an enhancer, providing antioxidant, antibacterial and optical properties;

[0011] (3) Glycerol: As a plasticizer, it improves the flexibility and transparency of the film;

[0012] (4) Acetic acid: used to dissolve chitosan to form a uniform solution.

[0013] Furthermore, tea polyphenol carbon dots are prepared by the following steps:

[0014] S1. Mix tea polyphenols and ultrapure water and stir evenly;

[0015] S2, placing the mixed solution in an autoclave and reacting at 180°C for 12 hours;

[0016] S3. Filter the reaction solution and freeze-dry it to obtain tea polyphenol carbon dot powder.

[0017] 3. The cling film according to claim 1, characterized in that the preparation steps of the cling film include:

[0018] S1, dissolving chitosan in a 1% acetic acid aqueous solution to form a chitosan solution with a concentration of 2%;

[0019] S2, adding 1% glycerol to the chitosan solution and stirring evenly;

[0020] S3, adding 1% to 5% tea polyphenol carbon dot solution, and pouring the solution onto a glass plate after ultrasonic degassing;

[0021] S4, drying in an oven at 40°C for 6 hours to form a film;

[0022] S5. Peel off the film and store it at 25°C and 50% relative humidity.

[0023] Furthermore, the thickness of the cling film is 0.1 to 0.3 mm.

[0024] Furthermore, the plastic wrap is used for preserving perishable foods such as salmon, meat, fruits and vegetables.

[0025] Furthermore, a composition for preparing a biomass carbon dot chitosan-based cling film comprises the following weight ratios:

[0026] (1) Chitosan 80%-95%;

[0027] (2) Tea polyphenols carbon dots 1%-10%;

[0028] (3) Glycerol 1%-5%;

[0029] (4) Acetic acid 1%-3%.

[0030] Furthermore, the method comprises the following steps:

[0031] (1) Wrapping food with the plastic wrap;

[0032] (2) Store under refrigerated conditions at 4°C to 10°C;

[0033] (3) Regularly test the microbial content and quality changes of food.

[0034] Furthermore, a biomass carbon dot chitosan-based cling film is used to extend the shelf life of food, inhibit microbial growth, reduce oxidation reactions and improve food storage quality.

[0035] Furthermore, the cling film is suitable for packaging fresh food that needs to be transported over long distances.

[0036] A composite fresh-keeping film with biomass carbon dots and chitosan as main components, and its preparation method is as follows:

[0037] Preparation of Tea Polyphenols Carbon Dots

[0038] Tea polyphenol carbon dots were synthesized by a simple hydrothermal method. Tea polyphenols were mixed with ultrapure water, heated in an autoclave at 180°C for 12 hours, cooled, filtered and freeze-dried to obtain tea polyphenol carbon dots powder. The carbon dots have excellent antibacterial and antioxidant properties.

[0039] Preparation of chitosan solution

[0040] Chitosan was dissolved in 1% acetic acid aqueous solution to form a 2% uniform solution. Chitosan has good film-forming ability and biodegradability.

[0041] Preparation of composite solution

[0042] 1% glycerol is added as a plasticizer to the chitosan solution, and 1% to 5% tea polyphenol carbon dot solution is further added. The solution is treated with ultrasonic waves to remove bubbles and make it uniformly dispersed.

[0043] Film Forming

[0044] The composite solution was evenly poured onto a glass plate and placed in a drying oven at 40° C. for 6 hours to form a film. Finally, the film was peeled off from the glass plate and stored at 25° C. and 50% relative humidity.

[0045] The composite cling film prepared by the above steps has excellent antibacterial, antioxidant and moisturizing properties, and is particularly suitable for packaging and preserving foods with high spoilage risks (such as salmon).

[0046] Beneficial effects of the present invention:

[0047] 1. Natural and environmentally friendly

[0048] The present invention uses tea polyphenol carbon dots and chitosan as main ingredients. Tea polyphenols are derived from natural tea leaves, while chitosan is derived from renewable resources in nature. These ingredients are not only non-toxic and harmless, but also can reduce the use of chemical preservatives, and are a natural and environmentally friendly preservation solution. The experimental data in the implementation case show that tea polyphenol carbon dots have strong natural antibacterial properties, which makes the protective effect of the cling film on food more prominent and environmentally friendly.

[0049] 2. Efficient preservation

[0050] By combining tea polyphenol carbon dots with chitosan, a preservative film with a composite effect is formed. Experimental data show that the preservation time of perishable foods such as salmon treated with this preservative film is significantly extended. For example, in the experiment, under normal storage conditions, the spoilage time of salmon was extended by 20%-30% after being packaged with the patented preservative film.

[0051] 3. Broad application prospects

[0052] This plastic wrap is not only suitable for perishable foods such as salmon, but can also be widely used in the packaging of other fresh foods such as fruits, vegetables, meat, etc., especially when they need to be stored and transported for a long time.

[0053] 4. Economical and scalable

[0054] The preparation method of this patent is simple and the raw material cost is relatively low. Tea polyphenols and chitosan have relatively stable supply channels in the market, so it has high economy and scalability. For large-scale production, the cling film of this patent can achieve large-scale production and reduce production costs. Experiments show that this method has good stability, and the prepared film material has uniform thickness and strength, which is suitable for large-scale application.

[0055] 5. Extend shelf life

[0056] Combined with the experimental data in the implementation case, the salmon wrapped with the plastic wrap slowed down its spoilage after a period of storage. The film material can further optimize the shelf life of food by adjusting the concentration of tea polyphenol carbon dots.

[0057] The tea polyphenol carbon dot chitosan cling film provided by this patent has multiple advantages such as natural environmental protection and antibacterial properties. It can effectively extend the shelf life of perishable foods and improve food quality. It also has broad application prospects and good economic efficiency. Experimental data show that the cling film has great application potential in extending the shelf life of food, maintaining food quality, and reducing food waste, providing a feasible green preservation solution for the food industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the technical solutions in the present invention or 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 in the following description are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0059] Figure 1 Schematic diagram of the in vitro antibacterial effect of tea polyphenol carbon dots at different concentrations according to an embodiment of the present invention;

[0060] Figure 2 Schematic diagram of the inhibitory effect of tea polyphenol carbon dots on Listeria monocytogenes biofilm according to an embodiment of the present invention;

[0061] Figure 3 Schematic diagram of the inhibitory effect of tea polyphenol carbon dots on Salmonella biofilm according to an embodiment of the present invention;

[0062] Figure 4 A schematic diagram of the tensile strength of a film according to an embodiment of the present invention;

[0063] Figure 5 It is a schematic diagram of the determination result of the total bacterial colony count of the fish fillet according to an embodiment of the present invention;

[0064] Figure 6 Schematic diagram of the pH measurement results of fish fillets according to an embodiment of the present invention. DETAILED DESCRIPTION

[0065] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. At the same time, it is explained here that in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments, and those skilled in the art may also adopt other alternatives to implement some known technologies; and the accompanying drawings are only for more specific description of the embodiments, and are not intended to specifically limit the present invention.

[0066] It should be noted that the references to "one embodiment", "an embodiment", "an exemplary embodiment", "some embodiments" and the like in the specification indicate that the embodiments described may include specific features, structures or characteristics, but not every embodiment may include the specific features, structures or characteristics. In addition, when a specific feature, structure or characteristic is described in conjunction with an embodiment, it should be within the knowledge of a person skilled in the art to implement such feature, structure or characteristic in conjunction with other embodiments (whether or not explicitly described).

[0067] In general, a term can be understood, at least in part, from its use in context. For example, depending, at least in part, on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in the singular sense, or can be used to describe a combination of features, structures, or characteristics in the plural sense. Additionally, the term "based on" can be understood as not necessarily intended to convey an exclusive set of factors, but can instead, depending, at least in part, on the context, allow for the presence of other factors that are not necessarily explicitly described.

[0068] Implementation Case 1:

[0069] Minimum inhibitory concentration

[0070] The sample was dispersed in ultrapure water to prepare the sample solution. Starting from the initial concentration, a series of sample solutions were prepared by 2-fold dilution method. Subsequently, 100 μL of Listeria monocytogenes and Salmonella solution (about 106 CFU / mL) was added to each gradient test tube and incubated in an incubator at 37°C for 24 hours. All experiments were repeated three times to ensure the reliability of the results.

[0071] The test results are as follows Figure 1 As shown:

[0072] In vitro antibacterial effects of tea polyphenol carbon dots at different concentrations. From the presence of colonies on the plate, it can be seen that the minimum inhibitory concentration of tea polyphenol carbon dots against Salmonella and Listeria monocytogenes is 0.5 mg / mL.

[0073] Implementation Case 2:

[0074] Inhibition of bacterial biofilm

[0075] Biofilm formation and assays were performed in 96-well microtiter plates as described previously. Briefly, the bacterial suspension was adjusted to 1 × 10 6 CFU / mL, and then 100 μL of bacterial culture was pipetted into each well of a 96-well microplate and incubated at 37°C for 24 hours to form biofilm. The formation of biofilm was subsequently evaluated using crystal violet staining.

[0076] The test results are as follows Figure 2 , 3 As shown:

[0077] Tea polyphenol carbon dots have a significant inhibitory effect on bacterial biofilms, and the inhibitory effect on biofilms is concentration-dependent. At 0.25 mg / mL, tea polyphenol carbon dots also inhibited the formation of Salmonella biofilm by about 30%, and at 2 mg / mL, tea polyphenol carbon dots completely inhibited the formation of biofilms. Similarly, tea polyphenol carbon dots also have a significant effect on inhibiting biofilms of Listeria monocytogenes.

[0078] Implementation Case 3:

[0079] Mechanical properties

[0080] The tensile strength and elongation at break of the films were measured by a microcomputer-controlled universal tensile tester at room temperature according to the standard. The films (10 mm × 60 mm) were tested at a crosshead speed of 0.5 mm / s. The initial stretching distance was set to 30 mmTS and E% was obtained from the stress-strain curve. At least five specimens were repeated for each piece.

[0081] The test results are as follows Figure 4 As shown:

[0082] The tensile strength and elongation at break reflect the strength and toughness of the film. The tensile strength of the film is depicted in the figure. It can be seen that with the increase of tea polyphenol carbon dots, the tensile strength of the film becomes stronger, which may indicate that the tea polyphenol carbon dots are enhanced to the film matrix through physical interaction. This study shows that when the concentration of tea polyphenol carbon dots increases to 5%, the tensile strength does not decrease, indicating that the tea polyphenol carbon dots have good dispersibility in the film and excellent compatibility with the film matrix. When the concentration of tea polyphenol carbon dots increases, the elongation at break decreases slightly.

[0083] Implementation Case 4:

[0084] Determination of total colony count in fish fillets

[0085] Weigh 10.00g of fish meat and place it in a sterile cooking bag, add 90mL of sterile saline, and beat it with a slapping homogenizer for 60s to obtain a 10-fold diluted mixture. Accurately draw 1mL of the mixture and dilute it 10 times with sterile saline. Select the appropriate gradient dilution and use the plate count method to determine the total number of colonies in the fish fillet.

[0086] The test results are as follows Figure 5 As shown:

[0087] The total viable count is an important factor affecting the shelf life of aquatic products. When the total viable count value is greater than 6logCFU / g, salmon is considered to have deteriorated and is no longer suitable for consumption. Initially, the total viable count value of fresh salmon was 2.03±0.04logCFU / g. During storage, the total viable count values ​​of the control group, CS group, CS-TCDs1 group, CS-TCDs3 group, and CS-TCDs5 group increased linearly with time. However, the growth rate of the total viable count value in the CS-TPDC5 group was much lower than that in the other control groups, indicating that TPDCs have a significant inhibitory effect on microorganisms in salmon. In the first 6 days of storage, the total viable count value of the control group exceeded 6logCFU / g, indicating that it had deteriorated, while the total viable count values ​​of the other 4 groups were all below this limit and no deterioration occurred.

[0088] Implementation Case 5:

[0089] Determination of pH of fish fillets

[0090] Weigh 5.00 g of minced fish meat, add 45 mL of deionized water and homogenize, let stand for 30 min, and use a pH meter to measure the pH of the solution, which is the pH of the fish fillet.

[0091] The test results are as follows Figure 6 As shown:

[0092] pH value is another important indicator for evaluating the quality changes of salmon during storage. Figure 6 The figure shows the changes in the pH value of salmon during storage. In the early stage of storage, due to the action of endogenous enzymes, the fish meat produced a large amount of acidic substances, causing the pH value to drop rapidly; then, with the increase of spoilage microorganisms and the influence of autolytic enzymes, a large amount of amine substances were produced, causing the pH value to gradually increase. On the second day, the pH value of all treatment groups reached the lowest point, and then gradually increased, and the overall pH value was maintained between 6.50 and 6.95. Compared with the blank control group, the pH value of fish meat packaged with antibacterial film changed more slowly, indicating that the film has a significant inhibitory effect on the spoilage process of fish meat. In contrast, the film with a higher concentration of tea polyphenols carbon dots has a more significant inhibitory effect on the pH value, so the CS-TCDs5 group film exhibits the best antibacterial and fresh-keeping effect.

[0093] The present invention covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention. In order to make the public have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, but those skilled in the art can fully understand the present invention without the description of these details. In addition, in order to avoid unnecessary confusion about the essence of the present invention, well-known methods, processes, procedures, components and circuits are not described in detail.

[0094] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A biomass carbon dot chitosan-based fresh-keeping film, characterized in that: The cling film is prepared from the following components in proportion: (1) Chitosan: provides good film-forming ability, biodegradability and antibacterial properties; (2) Tea polyphenol carbon dots: as an enhancer, providing antioxidant, antibacterial and optical properties; (3) Glycerol: As a plasticizer, it improves the flexibility and transparency of the film; (4) Acetic acid: used to dissolve chitosan to form a uniform solution.

2. The cling film according to claim 1, characterized in that: Tea polyphenol carbon dots were prepared by the following steps: S1. Mix tea polyphenols and ultrapure water and stir evenly; S2, placing the mixed solution in an autoclave and reacting at 180°C for 12 hours; S3. Filter the reaction solution and freeze-dry it to obtain tea polyphenol carbon dot powder.

3. The cling film according to claim 1, characterized in that: The preparation steps of the plastic wrap include: S1, dissolving chitosan in a 1% acetic acid aqueous solution to form a chitosan solution with a concentration of 2%; S2, adding 1% glycerol to the chitosan solution and stirring evenly; S3, adding 1% to 5% tea polyphenol carbon dot solution, and pouring the solution onto a glass plate after ultrasonic degassing; S4, drying in an oven at 40°C for 6 hours to form a film; S5. Peel off the film and store it at 25°C and 50% relative humidity.

4. The cling film according to any one of claims 1 to 3, characterized in that: The thickness of the fresh-keeping film is 0.1 to 0.3 millimeters.

5. The cling film according to any one of claims 1 to 4, characterized in that: The plastic wrap is used to preserve perishable foods such as salmon, meat, fruits and vegetables.

6. A composition for preparing a biomass carbon dot chitosan-based cling film, characterized in that: Includes the following weight ratios: (1) Chitosan 80%-95%; (2) Tea polyphenols carbon dots 1%-10%; (3) Glycerol 1%-5%; (4) Acetic acid 1%-3%.

7. A method for using the cling film according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: (1) using the plastic wrap to wrap food; (2) Store under refrigerated conditions at 4°C to 10°C; (3) Regularly test the microbial content and quality changes of food.

8. An application of a biomass carbon dot chitosan-based fresh-keeping film, characterized in that: The cling film is used to extend the shelf life of food, inhibit the growth of microorganisms, reduce oxidation reactions and improve the storage quality of food.

9. The use according to claim 8, characterized in that: The plastic wrap is suitable for packaging fresh food that needs to be transported over long distances.

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