Alpha plastic food antibacterial material and preparation method thereof

Abstract

The invention discloses a alpha plastic food antibacterial material and a preparation method thereof, and relates to the technical field of food packaging materials, the alpha plastic food antibacterial material comprises the following raw materials by weight: 5-8 parts of PHBV, 4-6 parts of chloroform, 0.1-0.2 part of alizarin, 1-3 parts of origanum vulgare essential oil, 10-15 parts of beta-cyclodextrin and 6-10 parts of absolute ethyl alcohol. Beta-cyclodextrin is utilized to embed origanum vulgare essential oil OEO, and the encapsulated OEO, pHBV and other materials are prepared into the food antibacterial film, so that the food antibacterial film has excellent performance in antibacterial performance, oxidation resistance, discoloration resistance and OEO / beta-CD slow-release performance, has mechanical strength and flexibility, prolongs the service life, reduces the probability of packaging failure and food leakage, and has good application prospects. The growth of microorganisms including bacteria and molds on the surface of food is effectively inhibited, so that the potential safety hazard of the food is reduced, and the storage performance of the food is improved.

Description

Technical Field

[0001] The invention relates to the technical field of food packaging materials, in particular to a pha plastic food antibacterial material and a preparation method thereof. Background Art

[0002] In order to protect the environment and reduce the use of chemical resources, renewable resources are selected. PHBV is a copolymer of PHA, which is mainly composed of β-hydroxybutyric acid and β-hydroxyvaleric acid monomers. At present, PHBV is widely used as a degradable material to replace traditional plastics, thereby reducing environmental pollution.

[0003] With the development of economy and the improvement of people's living standards, the development trend of food packaging is gradually moving towards intelligent packaging. The natural pigment alizarin is selected. The color changes from acidic to alkaline: yellow-orange-red-purple. Compared with anthocyanin and shikonin, the color change is obvious and can be used to detect changes in meat quality.

[0004] At present, essential oil is a natural plant-derived compound with high antibacterial properties. It is widely used in active food packaging, which is safe and efficient. Among them, oregano essential oil (OEO) contains a large amount of carvacrol and thymol, which has high antibacterial and antifungal functions. However, directly adding oregano essential oil to food packaging has high volatility and a strong aromatic smell, which causes its aroma to be quickly released into the packaging, affecting the flavor of the food. The strong aromatic smell will cover up or change the taste of the food itself. Summary of the invention

[0005] The object of the present invention is to provide a pha plastic food antibacterial material and a preparation method thereof, so as to solve the problem proposed in the above background technology that oregano essential oil is directly added to food packaging, which has high volatility and a strong aromatic smell, causing its aroma to be quickly released into the packaging, affecting the flavor of the food, and the strong aromatic smell will cover up or change the taste of the food itself.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a pha plastic food antibacterial material, comprising the following raw materials in parts by weight: 5-8 parts by weight of PHBV, 4-6 parts by weight of chloroform, 0.1-0.2 parts by weight of alizarin, 1-3 parts by weight of oregano essential oil, 10-15 parts by weight of β-cyclodextrin and 6-10 parts by weight of anhydrous ethanol; β-cyclodextrin is used to embed oregano essential oil OEO, the hydrophobic interior of the β-cyclodextrin molecule provides a good microenvironment for lipophilic substances, allowing the non-polar part of the guest molecule to enter and form a cage, making OEO more stable and slowly released, and controlling the release rate of the aromatic odor of oregano essential oil; using the large amount of carvacrol and thymol contained in oregano essential oil OEO, it has high-efficiency antibacterial and antifungal functions; by selecting the natural pigment alizarin, the color changes from acidic to alkaline, and can effectively display the corruption of food in the use of food packaging film, and can detect changes in meat quality.

[0007] A method for preparing a pha plastic food antibacterial material comprises the following steps:

[0008] Ⅰ. Accurately weigh β-cyclodextrin and add it into the reactor. At the same time, add water into the reactor and start stirring. Stir at a constant temperature of 45° C. at a speed of 500 rpm for 30 minutes to completely dissolve it. β-cyclodextrin can form an inclusion compound to encapsulate oregano essential oil.

[0009] Ⅱ. Take a certain amount of oregano essential oil and dissolve it in anhydrous ethanol. After mixing, add it into the β-cyclodextrin solution, stir it at a constant temperature of 45°C for 6 hours, and refrigerate it at 4°C for 8-10 hours after fully mixing. The use of anhydrous ethanol helps to improve the solubility of oregano essential oil, so that it can fully interact with cyclodextrin. Refrigeration helps the inclusion of cyclodextrin and essential oil, thereby improving the quality of the finished product.

[0010] III. After centrifugation, wash three times with ethanol solution to remove the unencapsulated oregano essential oil, and finally freeze-dry to obtain the encapsulated oregano essential oil. Through the centrifugation and washing process, the unencapsulated oregano essential oil can be greatly reduced to ensure the effective encapsulation of the oregano essential oil in the final product;

[0011] IV. Take a certain amount of PHBV and chloroform and place them in a reaction kettle. Heat the mixed solution to 60°C and stir at a constant temperature for 5 hours. After stirring, cool it to room temperature. The dissolution of PHBV provides a uniform matrix for subsequent material compounding, which helps to form a good antibacterial plastic material.

[0012] V. Add alizarin and encapsulated oregano essential oil to the mixed solution of the previous step, stir at room temperature for 2 hours, put into a drying oven, and dry at 40° C. for 16-24 hours. By adding alizarin, when the food packaged in the film is spoiled, the internal acid-base environment changes, causing the alizarin in the film to change color, thereby realizing food quality display;

[0013] VI. After drying, take it out and cool it naturally to obtain the plastic food antibacterial material. The moisture content of the material is ensured to be the lowest through drying, thereby improving the stability of the material.

[0014] Preferably, in step II, the volume ratio of the oregano essential oil to anhydrous ethanol is 1:5.

[0015] Preferably, in step III, washing three times with an ethanol solution after centrifugation to remove unencapsulated oregano essential oil comprises the following steps:

[0016] ① Transfer the embedded oregano essential oil solution into a centrifuge tube and place it in a centrifuge;

[0017] ② Set the centrifuge parameters, the centrifugal speed is 3000-5000rpm, the centrifugal time is 10-15min, and start centrifugation;

[0018] ③ After centrifugation, remove the supernatant to remove the unencapsulated oregano essential oil;

[0019] ④ Add a certain amount of anhydrous ethanol to the remaining precipitate again, mix well to resuspend the precipitate, centrifuge again, and remove the supernatant repeatedly;

[0020] ⑤ Repeat steps ③ and ④ three times, and after the last centrifugation, ensure that all the supernatant is removed to achieve complete removal of the unencapsulated oregano essential oil.

[0021] Preferably, in step V, the amount of alizarin added is 2% of the amount of PHBV added.

[0022] Preferably, in step V, the amount of the encapsulated oregano essential oil added is 1%-10% of the amount of PHBV added.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. In the present invention, oregano essential oil OEO is embedded by using β-cyclodextrin, and the encapsulated OEO is made into a food antibacterial film with materials such as pHBV, which has excellent performance in antibacterial, antioxidant, discoloration and sustained release of OEO / β-CD, has mechanical strength and flexibility, extends service life, reduces the probability of packaging failure and food leakage, and effectively inhibits the growth of microorganisms on the surface of food, including bacteria and mold, thereby reducing food safety hazards and improving the storage performance of food.

[0025] 2. In the present invention, by adding alizarin during the preparation of the film, when the food packaged in the film becomes spoiled, the internal acid-base environment changes, causing the alizarin in the film to change color, thereby effectively displaying the spoilage of the food and detecting changes in meat quality, so that users can conveniently and intuitively understand the quality of the stored food.

[0026] 3. In the present invention, oregano essential oil OEO is embedded in β-cyclodextrin, and the hydrophobic interior of the β-CD molecule provides a good microenvironment for the oregano essential oil, allowing the non-polar part of the guest molecule to enter and form a cage, so that the oregano essential oil OEO can be slowly released. The oregano essential oil OEO contains a large amount of carvacrol and thymol, so that the plastic food antibacterial material of the present invention can continuously and stably play an antibacterial role, and avoid the strong aromatic smell from covering up or changing the taste of the food itself and affecting the flavor of the food. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the embodiments.

[0029] Example 1: This example provides a pha plastic food antibacterial material, comprising the following raw materials in parts by weight: 5 parts by weight of PHBV, 4 parts by weight of chloroform, 0.1 parts by weight of alizarin, 1 part by weight of oregano essential oil, 10 parts by weight of β-cyclodextrin and 6 parts by weight of anhydrous ethanol.

[0030] A method for preparing a pha plastic food antibacterial material comprises the following steps:

[0031] Step 1: Accurately weigh β-cyclodextrin and add it into the reactor. At the same time, add water into the reactor and start stirring. Stir at a constant temperature of 45°C at a speed of 500 rpm for 30 minutes to completely dissolve it.

[0032] Step 2: Dissolve a certain amount of oregano essential oil in anhydrous ethanol, add the mixture to the β-cyclodextrin solution, stir at a constant temperature of 45°C for 6 hours, and refrigerate at 4°C for 8-10 hours after sufficient mixing;

[0033] Among them, the volume ratio of oregano essential oil to anhydrous ethanol is 1:5;

[0034] Step 3, washing three times with an ethanol solution after centrifugation to remove the unencapsulated oregano essential oil, and finally freeze-drying to obtain the encapsulated oregano essential oil;

[0035] The specific process of washing three times with ethanol solution after centrifugation to remove the unembedded oregano essential oil is as follows:

[0036] ① Transfer the embedded oregano essential oil solution into a centrifuge tube and place it in a centrifuge;

[0037] ② Set the centrifuge parameters, the centrifugal speed is 3000-5000rpm, the centrifugal time is 10-15min, and start centrifugation;

[0038] ③ After centrifugation, remove the supernatant to remove the unencapsulated oregano essential oil;

[0039] ④ Add a certain amount of anhydrous ethanol to the remaining precipitate again, mix well to resuspend the precipitate, centrifuge again, and remove the supernatant repeatedly;

[0040] ⑤ Repeat steps ③ and ④ three times, and after the last centrifugation, make sure to remove all the supernatant;

[0041] Step 4: Take a certain amount of PHBV and chloroform and place them in a reaction kettle. Heat the mixed solution to 60° C. and stir at constant temperature for 5 hours. After stirring, cool to room temperature.

[0042] Step 5: Add alizarin and encapsulated oregano essential oil to the mixed solution of the previous step, stir at room temperature for 2 hours, and then put it into a drying oven and dry it at 40°C for 16-24 hours;

[0043] Among them, the amount of alizarin added is 2% of the amount of PHBV added, and the amount of encapsulated oregano essential oil added is 1% of the amount of PHBV added;

[0044] Step 6: Take out after drying, and obtain the plastic food antibacterial material after natural cooling.

[0045] Example 2: This example provides a pha plastic food antibacterial material, comprising the following raw materials in parts by weight: 6 parts by weight of PHBV, 5 parts by weight of chloroform, 0.12 parts by weight of alizarin, 1.5 parts by weight of oregano essential oil, 12 parts by weight of β-cyclodextrin and 8 parts by weight of anhydrous ethanol.

[0046] A method for preparing a pha plastic food antibacterial material comprises the following steps:

[0047] Step 1: Accurately weigh β-cyclodextrin and add it into the reactor. At the same time, add water into the reactor and start stirring. Stir at a constant temperature of 45°C at a speed of 500 rpm for 30 minutes to completely dissolve it.

[0048] Step 2: Dissolve a certain amount of oregano essential oil in anhydrous ethanol, add the mixture to the β-cyclodextrin solution, stir at a constant temperature of 45°C for 6 hours, and refrigerate at 4°C for 8-10 hours after sufficient mixing;

[0049] Among them, the volume ratio of oregano essential oil to anhydrous ethanol is 1:5;

[0050] Step 3, washing three times with an ethanol solution after centrifugation to remove the unencapsulated oregano essential oil, and finally freeze-drying to obtain the encapsulated oregano essential oil;

[0051] The specific process of washing three times with ethanol solution after centrifugation to remove the unembedded oregano essential oil is as follows:

[0052] ① Transfer the embedded oregano essential oil solution into a centrifuge tube and place it in a centrifuge;

[0053] ② Set the centrifuge parameters, the centrifugal speed is 3000-5000rpm, the centrifugal time is 10-15min, and start centrifugation;

[0054] ③ After centrifugation, remove the supernatant to remove the unencapsulated oregano essential oil;

[0055] ④ Add a certain amount of anhydrous ethanol to the remaining precipitate again, mix well to resuspend the precipitate, centrifuge again, and remove the supernatant repeatedly;

[0056] ⑤ Repeat steps ③ and ④ three times, and after the last centrifugation, make sure to remove all the supernatant;

[0057] Step 4: Take a certain amount of PHBV and chloroform and place them in a reaction kettle. Heat the mixed solution to 60° C. and stir at constant temperature for 5 hours. After stirring, cool to room temperature.

[0058] Step 5: Add alizarin and encapsulated oregano essential oil to the mixed solution of the previous step, stir at room temperature for 2 hours, and then put it into a drying oven and dry it at 40°C for 16-24 hours;

[0059] Among them, the amount of alizarin added is 2% of the amount of PHBV added, and the amount of encapsulated oregano essential oil added is 2% of the amount of PHBV added;

[0060] Step 6: Take out after drying, and obtain the plastic food antibacterial material after natural cooling.

[0061] Example 3: This example provides a pha plastic food antibacterial material, comprising the following raw materials in parts by weight: 7 parts by weight of PHBV, 5 parts by weight of chloroform, 0.15 parts by weight of alizarin, 2 parts by weight of oregano essential oil, 13 parts by weight of β-cyclodextrin and 8 parts by weight of anhydrous ethanol.

[0062] A method for preparing a pha plastic food antibacterial material comprises the following steps:

[0063] Step 1: Accurately weigh β-cyclodextrin and add it into the reactor. At the same time, add water into the reactor and start stirring. Stir at a constant temperature of 45°C at a speed of 500 rpm for 30 minutes to completely dissolve it.

[0064] Step 2: Dissolve a certain amount of oregano essential oil in anhydrous ethanol, add the mixture to the β-cyclodextrin solution, stir at a constant temperature of 45°C for 6 hours, and refrigerate at 4°C for 8-10 hours after sufficient mixing;

[0065] Among them, the volume ratio of oregano essential oil to anhydrous ethanol is 1:5;

[0066] Step 3, washing three times with an ethanol solution after centrifugation to remove the unencapsulated oregano essential oil, and finally freeze-drying to obtain the encapsulated oregano essential oil;

[0067] The specific process of washing three times with ethanol solution after centrifugation to remove the unembedded oregano essential oil is as follows:

[0068] ① Transfer the embedded oregano essential oil solution into a centrifuge tube and place it in a centrifuge;

[0069] ② Set the centrifuge parameters, the centrifugal speed is 3000-5000rpm, the centrifugal time is 10-15min, and start centrifugation;

[0070] ③ After centrifugation, remove the supernatant to remove the unencapsulated oregano essential oil;

[0071] ④ Add a certain amount of anhydrous ethanol to the remaining precipitate again, mix well to resuspend the precipitate, centrifuge again, and remove the supernatant repeatedly;

[0072] ⑤ Repeat steps ③ and ④ three times, and after the last centrifugation, make sure to remove all the supernatant;

[0073] Step 4: Take a certain amount of PHBV and chloroform and place them in a reaction kettle. Heat the mixed solution to 60° C. and stir at constant temperature for 5 hours. After stirring, cool to room temperature.

[0074] Step 5: Add alizarin and encapsulated oregano essential oil to the mixed solution of the previous step, stir at room temperature for 2 hours, and then put it into a drying oven and dry it at 40°C for 16-24 hours;

[0075] Among them, the amount of alizarin added is 2% of the amount of PHBV added, and the amount of encapsulated oregano essential oil added is 5% of the amount of PHBV added;

[0076] Step 6: Take out after drying, and obtain the plastic food antibacterial material after natural cooling.

[0077] Example 4: This example provides a pha plastic food antibacterial material, comprising the following raw materials in parts by weight: 8 parts by weight of PHBV, 6 parts by weight of chloroform, 0.2 parts by weight of alizarin, 3 parts by weight of oregano essential oil, 15 parts by weight of β-cyclodextrin and 10 parts by weight of anhydrous ethanol.

[0078] A method for preparing a pha plastic food antibacterial material comprises the following steps:

[0079] Step 1: Accurately weigh β-cyclodextrin and add it into the reactor. At the same time, add water into the reactor and start stirring. Stir at a constant temperature of 45°C at a speed of 500 rpm for 30 minutes to completely dissolve it.

[0080] Step 2: Dissolve a certain amount of oregano essential oil in anhydrous ethanol, add the mixture to the β-cyclodextrin solution, stir at a constant temperature of 45°C for 6 hours, and refrigerate at 4°C for 8-10 hours after sufficient mixing;

[0081] Among them, the volume ratio of oregano essential oil to anhydrous ethanol is 1:5;

[0082] Step 3, washing three times with an ethanol solution after centrifugation to remove the unencapsulated oregano essential oil, and finally freeze-drying to obtain the encapsulated oregano essential oil;

[0083] The specific process of washing three times with ethanol solution after centrifugation to remove the unembedded oregano essential oil is as follows:

[0084] ① Transfer the embedded oregano essential oil solution into a centrifuge tube and place it in a centrifuge;

[0085] ② Set the centrifuge parameters, the centrifugal speed is 3000-5000rpm, the centrifugal time is 10-15min, and start centrifugation;

[0086] ③ After centrifugation, remove the supernatant to remove the unencapsulated oregano essential oil;

[0087] ④ Add a certain amount of anhydrous ethanol to the remaining precipitate again, mix well to resuspend the precipitate, centrifuge again, and remove the supernatant repeatedly;

[0088] ⑤ Repeat steps ③ and ④ three times, and after the last centrifugation, make sure to remove all the supernatant;

[0089] Step 4: Take a certain amount of PHBV and chloroform and place them in a reaction kettle. Heat the mixed solution to 60° C. and stir at constant temperature for 5 hours. After stirring, cool to room temperature.

[0090] Step 5: Add alizarin and encapsulated oregano essential oil to the mixed solution of the previous step, stir at room temperature for 2 hours, and then put it into a drying oven and dry it at 40°C for 16-24 hours;

[0091] Among them, the amount of alizarin added is 2% of the amount of PHBV added, and the amount of encapsulated oregano essential oil added is 10% of the amount of PHBV added;

[0092] Step 6: Take out after drying, and obtain the plastic food antibacterial material after natural cooling.

[0093] Comparative Example 1: The pha plastic food antibacterial material and the preparation method thereof provided in this embodiment are substantially the same as those in Example 1, the main difference being that β-cyclodextrin is not used to encapsulate oregano essential oil.

[0094] Comparative Example 2: The pha plastic food antibacterial material and its preparation method provided in this embodiment are roughly the same as those in Example 1, with the main difference being that no alizarin is added to the raw materials.

[0095] Comparative Example 3: The pha plastic food antibacterial material and the preparation method thereof provided in this embodiment are substantially the same as those in Example 1, the main difference being that tea tree essential oil is used to replace oregano essential oil in the raw material.

[0096] Performance testing and result analysis

[0097] The plastic food antibacterial materials prepared in Examples 1-4 and Comparative Examples 1-3 were respectively made into films for performance testing, and the relevant data were recorded in Table 1;

[0098] (1) Mechanical properties test: Six points were randomly selected on the film sample to measure the film thickness, and the average value was calculated. The mechanical properties test was carried out using a UTM2502 electronic universal testing machine according to the national standard GB / T1040.3-2006, and the tensile strength TS was recorded. The elongation at break EB was calculated according to the formula:

[0099] EB(%)=(L2-L1) / L1;

[0100] Where L2 is the measured length before fracture, L1 is a constant value of 2.5 cm, the initial clamp distance is 80 mm, the gauge length is 25 mm, the crosshead speed is 100 mm / min, and each film sample is tested seven times in parallel;

[0101] (2) pH-responsive intelligent color development of the film: soak the film sample in solutions of different pH values ​​and observe the color change of the film;

[0102] (3) Antibacterial properties of the film: Cut the film into a circle with a diameter of 6 mm, put it into a sterile centrifuge tube, mark it, and then use a pipette to transfer 100 μL of the E. coli suspension and drop it into the sterile centrifuge tube containing the circular film. Make sure that the film is immersed in the E. coli suspension and then seal it with plastic wrap. Place it in a 37°C biochemical incubator and incubate it for 4 hours. After taking out the centrifuge tube, add 3 mL of saline to dilute the E. coli suspension after the reaction, and then draw 100 μL and inject it into a plastic culture dish containing nutrient agar. Roll the glass beads to make the bacterial liquid fully spread in the culture dish. Place the culture dish in a 37°C biochemical incubator and culture it for 12-24 hours. Count the number of colonies on the culture dish and calculate the antibacterial rate. Each film is measured in parallel three times.

[0103] (4) Antioxidant properties of the films: First, weigh 4 mg of DPPH in a beaker, stir and dissolve it with 100 mL of anhydrous ethanol, and store it at low temperature away from light. Cut the films into squares of the same size and weigh them to make sure that the mass of all the films is basically the same. Then, place them in a brown plastic tube, inject 4 mL of DPPH solution into the test tube with a pipette, cover the lid and shake well, and store it in the dark for 90 min. After the reaction is completed, use a UV-visible spectrophotometer to measure the absorbance Aa of the DPPH solution and the absorbance Ab of the solution after the reaction at 517 nm. Each film is measured six times in parallel, and the DPPH free radical scavenging rate (FCC) is calculated using the following formula:

[0104] FCC(%)=(1-Ab / Aa)×100;

[0105] Table 1: Test data record table

[0106]

[0107] As shown in Table 1, compared with the comparative example, the food antibacterial materials prepared in Examples 1-4 significantly improve the antibacterial rate and DPPH free radical scavenging rate after being made into films, and also have good elongation at break and pH sensitivity. The above results show that the food antibacterial materials prepared in Examples 1-4 have good toughness and flexibility when subjected to external forces in film applications, can withstand large deformations without being easily broken, are conducive to improving the mechanical strength and flexibility of the film, extending the service life, and reducing the probability of packaging failure and food leakage. The excellent antibacterial rate of the food antibacterial film enables it to effectively inhibit or kill microorganisms, and the high DPPH free radical scavenging rate means that the film has good antioxidant properties, which can prevent food from deteriorating due to oxidation reactions during storage. The good pH sensitivity enables the film to undergo color changes or other performance changes in different acid-base environments, thereby providing a visual indication of food quality and safety.

[0108] The plastic food antibacterial materials prepared in Examples 1-4 were respectively tested for the sustained release properties of oregano essential oil OEO in a simulated food system: a 10% ethanol solution was used to simulate a high water activity system, and a 50% ethanol solution was used to simulate a high alcohol food system. OEO / β-CD was placed in the two solution systems and stirred at 25°C for 48 hours. Samples were taken at 0, 2, 4, 6, 8, 10, 12, 24, 36 and 48 hours, and the concentration of OEO released into the solution was determined by ultraviolet spectrophotometry;

[0109] The test results show that the release rate of OEO in 50% ethanol solution and the release rate in 10% ethanol solution are both kept at a low speed, and the concentration of OEO released into the solution is released slowly, so that the plastic food antibacterial material of the present invention can continuously and stably play an antibacterial role, avoiding the strong aromatic smell from covering up or changing the taste of the food itself and affecting the flavor of the food;

[0110] The plastic food antibacterial materials prepared in Examples 1-4 and Comparative Example 2 were respectively made into films for intelligent pork packaging test: the film samples were wrapped around pork of the same size, and the color changes of the films at different times of 0, 1, 2, and 3 days were observed;

[0111] The test results show that the color of the film of Comparative Example 2 as the control group did not show obvious changes during the experiment. The TVBN value of the pork in the films of Examples 1-4 was greater than 30 on the third day, and it changed significantly from yellow to red. According to the Chinese standard GB2733-2015, when the TVBN value is greater than 20, the food has been spoiled, which means that the pork has been spoiled on the third day, and it can be intuitively seen from the change in the color of the film, indicating that the film made of the plastic food antibacterial material of the present invention can effectively display the spoilage of food;

[0112] In summary, the present invention uses β-cyclodextrin to embed oregano essential oil OEO, and makes the encapsulated OEO and materials such as pHBV into a food antibacterial film, which has excellent performance in antibacterial, antioxidant, discoloration and sustained release of OEO / β-CD, has mechanical strength and flexibility, extends the service life, reduces the probability of packaging failure and food leakage, and effectively inhibits the growth of microorganisms on the surface of food, including bacteria and mold, thereby reducing food safety hazards and improving the storage performance of food. In addition, the addition of alizarin can effectively display the corruption of food, detect changes in meat quality, and enable users to conveniently and intuitively understand the quality of stored food.

[0113] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A pha plastic food antibacterial material, characterized in that: The invention comprises the following raw materials in parts by weight: 5-8 parts by weight of PHBV, 4-6 parts by weight of chloroform, 0.1-0.2 parts by weight of alizarin, 1-3 parts by weight of oregano essential oil, 10-15 parts by weight of beta-cyclodextrin and 6-10 parts by weight of anhydrous ethanol.

2. A method for preparing the pha plastic food antibacterial material according to claim 1, characterized in that: The following steps are involved: Ⅰ. Accurately weigh β-cyclodextrin and add it into the reactor. Add water into the reactor and start stirring. Stir at a constant temperature of 45°C at a speed of 500 rpm for 30 minutes to completely dissolve it. Ⅱ. Take a certain amount of oregano essential oil and dissolve it in anhydrous ethanol. After mixing, add it into the β-cyclodextrin solution, stir it at a constant temperature of 45°C for 6 hours, and after fully mixing, refrigerate it at 4°C for 8-10 hours to complete the embedding of oregano essential oil in β-cyclodextrin. III. After centrifugation, wash three times with ethanol solution to remove the unencapsulated oregano essential oil, and finally freeze-dry to obtain the encapsulated oregano essential oil; IV. Take a certain amount of PHBV and chloroform and place them in a reaction kettle. Heat the mixed solution to 60°C and stir at constant temperature for 5 hours. After stirring, cool to room temperature. V. Add alizarin and encapsulated oregano essential oil to the mixed solution in the previous step, stir at room temperature for 2 hours, then put into a drying oven and dry at 40°C for 16-24 hours; VI. After drying, take it out and cool it naturally to obtain the plastic food antibacterial material.

3. The method for preparing a pha plastic food antibacterial material according to claim 2, characterized in that: In step II, the volume ratio of the oregano essential oil to anhydrous ethanol is 1:

5.

4. The method for preparing a pha plastic food antibacterial material according to claim 2, characterized in that: In step III, washing three times with an ethanol solution after centrifugation to remove unencapsulated oregano essential oil comprises the following steps: ① Transfer the embedded oregano essential oil solution into a centrifuge tube and place it in a centrifuge; ② Set the centrifuge parameters, the centrifugal speed is 3000-5000rpm, the centrifugal time is 10-15min, and start centrifugation; ③ After centrifugation, remove the supernatant to remove the unencapsulated oregano essential oil; ④ Add a certain amount of anhydrous ethanol to the remaining precipitate again, mix well to resuspend the precipitate, centrifuge again, and remove the supernatant repeatedly; ⑤Repeat steps ③ and ④ three times, and after the last centrifugation, make sure to remove all the supernatant.

5. The method for preparing a pha plastic food antibacterial material according to claim 2, characterized in that: In step V, the amount of alizarin added is 2% of the amount of PHBV added.

6. The method for preparing a pha plastic food antibacterial material according to claim 2, characterized in that: In step V, the amount of the encapsulated oregano essential oil added is 1%-10% of the amount of PHBV added.

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