Packaging material prepared from natural extract with antioxidant and antibacterial functions and application of packaging material

Abstract

The invention discloses a packing material prepared from natural extracts with antioxidant and antibacterial functions and application of the packing material, and relates to the technical field of food packing materials. Rosemary extracts with the antioxidant and antibacterial functions are extracted from rosemary leaves through an ultrasonic-assisted extraction method; the preparation method comprises the following steps: extracting tea polyphenol with antioxidant and bacteriostatic functions from green tea by using double distilled water, selecting sodium alginate as a carrier, adopting glucolactone as a pH regulator, further uniformly mixing a rosemary extract with the tea polyphenol and a sodium alginate cross-linking membrane solution, drying to form a membrane, and performing freeze drying to obtain the rosemary tea polyphenol film. And finally obtaining the packing material of the natural extract with antioxidant and bacteriostatic functions. The packing material prepared by the invention not only has excellent mechanical property and moisture barrier property, but also has remarkable oxidation resistance and bacteriostatic action, and can effectively prolong the shelf life of food and maintain the freshness of the food.

Description

Technical Field

[0001] The invention belongs to the technical field of food packaging materials, and specifically relates to a packaging material prepared from a natural extract with antioxidant and antibacterial functions and its application. Background Art

[0002] Rosemary extract is extracted from the rosemary plant, which is a versatile economic crop native to the Mediterranean region and is now also grown in Yunnan, Guangxi, Hainan, Hunan, Sichuan, Guizhou, Fujian and other places in China. Rosemary extract mainly includes antioxidants and rosemary essential oils. The main components of antioxidants are diterpenes, flavonoids, triterpenes and other compounds with antioxidant properties. In particular, rosemary extract has a significant effect in the field of food preservation and can be used in various animal and plant oils, animal feed, meat products, seafood, flour, sauces, seasonings, baked goods, fried products, etc.

[0003] Rosemary extract, as a plant-based preservative and antioxidant, has been approved by the government for use as a food additive. The effect of a single antioxidant is limited. When two or more antioxidants with different action sites and different properties coexist, an "antioxidant complex chain" can be formed to enhance the overall antioxidant performance. Antioxidant synergy can be described as when two or more bioactive compounds produce similar effects in the body, additional effects can be produced when used simultaneously, which can improve the antioxidant performance of the overall system to a certain extent, achieving the effect of "1+1>2". In recent years, studies have shown that polyphenol antioxidants have synergistic effects in certain reaction systems. Studies have found that the combination of rosemary extract and tea polyphenols can significantly improve the antioxidant performance, and the antioxidant effect is stronger than any single variety.

[0004] Bio-based films have received extensive attention in the field of food packaging due to their biodegradable properties. However, these films have limited mechanical strength, antibacterial properties, antioxidant properties, water vapor barrier properties, and other properties, and face many problems in practical applications. Sodium alginate (SA) is widely used in food, biomedicine, and chemical industries due to its biocompatibility, biodegradability, and excellent film-forming properties. Alginate has been widely used and explored in the fields of tissue engineering, drug delivery, wound healing, textiles, cosmetics, and food science due to its good renewability, biocompatibility, biodegradability, gelation, and processing properties. In addition, alginate polymers quickly gel through simple ionic cross-linking to form an irreversible complex network structure, which is conducive to the immobilization of bioactive molecules and improves bioavailability.

[0005] As people's living standards improve, food safety issues are becoming more and more important. However, food preservation faces many challenges during storage and transportation due to factors such as microorganisms, temperature, and food structure. In the prior art, there is no technical solution to extend the shelf life of food by preparing packaging materials using a combination of multiple natural extracts with antioxidant and antibacterial functions to expand their application in food packaging. Summary of the invention

[0006] The purpose of the present invention is to provide a packaging material prepared from a natural extract with antioxidant and antibacterial functions and its application, so as to solve the technical problem that in the prior art, a packaging material is not prepared by combining multiple natural extracts with antioxidant and antibacterial functions, and its application in food packaging is expanded to extend the food preservation time and shelf life.

[0007] In order to achieve the above-mentioned object, the present invention adopts the following technical scheme: The present invention provides a packaging material prepared from a natural extract having antioxidant and antibacterial functions, comprising the following steps:

[0008] (1) extracting rosemary extract with antioxidant and antibacterial functions from rosemary leaves;

[0009] (2) Extracting tea polyphenols with antioxidant and antibacterial properties from green tea;

[0010] (3) preparing a chitosan glacial acetic acid solution and a gelatin aqueous solution, mixing them to obtain a chitosan gelatin film solution;

[0011] (4) Rosemary extract and tea polyphenols are added to chitosan gelatin film liquid, and after drying, a natural extract packaging material with antioxidant and antibacterial functions is obtained.

[0012] Furthermore, the packaging material prepared from the natural extract having antioxidant and antibacterial functions, step (1) comprises the following process:

[0013] S1. Material preparation: wash the rosemary leaves, and then put them into a drying oven to dry them to obtain clean rosemary leaves;

[0014] S2, crushing and sieving: crushing the clean rosemary leaves and sieving them to obtain rosemary leaf powder;

[0015] S3, ultrasonic extraction: Weigh rosemary leaf powder, add ethanol in a beaker, put it into ultrasonic extraction, and soak at room temperature to obtain rosemary extract;

[0016] S4, filtration and centrifugation: filtering the rosemary extract, centrifuging, discarding the precipitate, taking the supernatant, and obtaining a rosemary supernatant;

[0017] S5. Freeze drying: pour the rosemary supernatant into a freeze drying bottle, then put it into the cold trap of a freeze dryer, reduce the pressure of the freeze dryer to a high vacuum state, and dry; after drying, continue to maintain the high vacuum state; after freeze drying, turn off the freeze dryer and slowly return to atmospheric pressure; open the freeze drying bottle and collect the rosemary extract.

[0018] Furthermore, the packaging material prepared from the natural extract with antioxidant and antibacterial functions, the S1 material preparation is dried in a drying oven at 60-65°C for 6-8 hours, preferably 7 hours; the S2 is crushed and sieved through a 60-120 mesh sieve, preferably 100 mesh; the S3 uses 60-98% ethanol, preferably 70%, the material-liquid ratio is 1:10-25, preferably 1:20, ultrasonication is performed at 40-60°C for 10-50 minutes, the ultrasonic power is 200-400W, and the room temperature is soaked for 16-24 hours; the S4 rosemary extract is filtered with gauze and centrifuged at 3000-5000r / min for 10-15 minutes; the temperature in the S5 freeze-drying cold trap is -40--80°C, the freezing time is 8-12 hours, and a high vacuum state is below 0.1mbar, and the high vacuum state is dried for 24-30 hours, and the high vacuum state is maintained for 2-4 hours.

[0019] Furthermore, the packaging material prepared from the natural extract having antioxidant and antibacterial functions, step (2) comprises the following process:

[0020] Q1. Material preparation: Wash the green tea leaves and dry them in a drying oven to obtain clean rosemary leaves;

[0021] Q2. Grinding and sieving: Grind the clean green tea leaves and sieve them to get green tea powder;

[0022] Q3. Extraction: Weigh green tea powder into a flask, add double distilled water, adjust the pH, set the temperature and perform shaking extraction in a water bath, repeat the extraction, centrifuge, and collect the supernatant to obtain the tea polyphenols extract.

[0023] Furthermore, the packaging material prepared from the natural extract with antioxidant and antibacterial functions, Q1 is dried and placed in a 60-65°C forced air drying oven for 6-8 hours, preferably 7 hours; Q2 the green tea leaves are crushed and sieved through a 60-100 mesh sieve, preferably 80 mesh; Q3 the ratio of extracted green tea powder to double distilled water is 1:30-35, preferably 1:30; pH is adjusted to 5-6; the water bath temperature is 60-80°C, preferably 70°C; the water bath time is 40-50 minutes, preferably 45 minutes; the stirring rate is 50-200 r / min, preferably 100 r / min; the extraction is repeated 2-3 times, preferably 3 times; and centrifugation is performed at 3000-5000 rpm for 5-10 minutes.

[0024] Furthermore, the preparation of the natural extract packaging material with antioxidant and antibacterial functions, step (3) includes the following process:

[0025] K1. Prepare sodium alginate membrane liquid: weigh sodium alginate and polyacrylamide solids respectively, mix the sodium alginate and polyacrylamide, add sterile deionized water, and mix evenly with a magnetic stirrer to obtain a sodium alginate membrane liquid;

[0026] K2. Preliminary cross-linking with calcium ions: weigh nano-calcium carbonate particles and add them to the sodium alginate membrane solution, and stir them thoroughly with a magnetic stirrer to obtain a sodium alginate preliminary cross-linked membrane solution;

[0027] K3. Uniform cross-linking: Weigh gluconolactone powder and add it to sodium alginate to initially cross-link the membrane liquid, and continue to stir it fully with a magnetic stirrer to obtain a sodium alginate cross-linked membrane liquid.

[0028] Furthermore, in the packaging material prepared from a natural extract with antioxidant and antibacterial functions, the sodium alginate and polyacrylamide are mixed in a mass ratio of 3:1, the magnetic stirrer speed is 350-450rpm, the set temperature is 20-25°C, the stirring time is 20-30min, and the mass concentration of the sodium alginate membrane liquid is 2.8-3.2%; the content of the nano-calcium carbonate particles in the sodium alginate membrane liquid is 0.08-0.12%, the magnetic stirrer speed is 350-450rpm, the set temperature is 20-25°C, and the stirring time is 20-30min; the content of the gluconolactone powder in the sodium alginate cross-linked membrane liquid is 0.08-0.12%, the magnetic stirrer speed is 350-450rpm, the set temperature is 20-25°C, and the stirring time is 50-60min.

[0029] Furthermore, the preparation of the natural extract packaging material with antioxidant and antibacterial functions, step (4) includes the following process:

[0030] F1. Adding natural extracts: The rosemary extract prepared above is prepared into a rosemary extract solution and added into a sodium alginate cross-linked membrane liquid, and then the tea polyphenols extract is added into the sodium alginate cross-linked membrane liquid to obtain a natural extract membrane liquid with antioxidant and antibacterial functions;

[0031] F2. Film formation: The natural extract film liquid with antioxidant and antibacterial functions is homogenized by a high-speed homogenizer, ultrasonically defoamed, weighed and poured into an acrylic mold, and placed in a blast dryer to evaporate water, thereby obtaining a packaging material of the natural extract with antioxidant and antibacterial functions.

[0032] Furthermore, the packaging material prepared from the natural extract with antioxidant and antibacterial functions, the concentration of the rosemary extract solution is 3-5 mg / mL, the volume ratio of the rosemary extract solution to the sodium alginate cross-linked membrane liquid is 1:16-30, and the volume ratio of the tea polyphenol extract solution to the sodium alginate cross-linked membrane liquid is 1:16-30; the high-speed homogenizer is homogenized for 2-3 minutes, preferably 2 minutes, and the ultrasonic defoaming is 12-16 minutes, preferably 14 minutes; 35-40g of the natural extract membrane liquid with antioxidant and antibacterial functions is weighed and placed in a 20-25°C air dryer for drying for 2-3 days, the relative humidity is 50%, preferably dried in a 23°C air dryer for 3 days.

[0033] The present invention also provides the use of a packaging material prepared from the natural extract with antioxidant and antibacterial functions in food packaging.

[0034] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0035] 1. The present invention selects sodium alginate as a carrier, adopts gluconolactone as a pH regulator, induces nano-calcium carbonate to gradually release calcium ions to make the membrane liquid cross-linking more uniform, and further adds rosemary extract and tea polyphenols to prepare a packaging material of a natural extract with antioxidant and antibacterial functions. The packaging material not only has good mechanical properties and moisture barrier properties, but also has significant antioxidant and antibacterial effects. After being applied to food packaging, it can effectively extend the shelf life of food and maintain the freshness and nutritional components of food.

[0036] 2. The present invention uses rosemary extract and tea polyphenols as antioxidants and antibacterial agents, which have higher biocompatibility and safety compared to chemically synthesized antioxidants and antibacterial agents. In addition, the packaging material uses sodium alginate and polyacrylamide as raw materials, and nano calcium carbonate particles as a cross-linking agent, which not only satisfies the prepared packaging material with excellent mechanical properties, but also can be degraded quickly after being discarded, reducing pollution to the environment, which is in line with the development trend of green packaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] 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.

[0038] Figure 1 The DPPH free radical scavenging rate of the packaging material prepared from the natural extract with antioxidant and antibacterial functions provided in the embodiment of the present invention. DETAILED DESCRIPTION

[0039] 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.

[0040] Embodiment 1:

[0041] This embodiment provides a packaging material prepared from a natural extract having antioxidant and antibacterial functions, comprising the following steps:

[0042] (1) extracting rosemary extract with antioxidant and antibacterial functions from rosemary leaves;

[0043] (2) Extracting tea polyphenols with antioxidant and antibacterial properties from green tea;

[0044] (3) preparing a chitosan glacial acetic acid solution and a gelatin aqueous solution, mixing them to obtain a chitosan gelatin film solution;

[0045] (4) Rosemary extract and tea polyphenols are added to chitosan gelatin film liquid, and after drying, a natural extract packaging material with antioxidant and antibacterial functions is obtained.

[0046] Specifically, step (1) includes the following process:

[0047] S1. Material preparation: wash the rosemary leaves, and then put them into a drying oven at 60°C for 8 hours to obtain clean rosemary leaves;

[0048] S2, crushing and sieving: crushing the clean rosemary leaves and passing through a 60-mesh sieve to obtain rosemary leaf powder;

[0049] S3, ultrasonic extraction: weigh rosemary leaf powder, add 60% ethanol in a beaker, the solid-liquid ratio is 1:10, ultrasonicate at 40°C for 10 min, ultrasonic power is 200 W, and soak at room temperature for 16 h to obtain rosemary extract;

[0050] S4, filtration and centrifugation: Filter the rosemary extract with gauze, centrifuge at 3000r / min for 10min, discard the precipitate, take the supernatant, and obtain rosemary supernatant;

[0051] S5. Freeze drying: pour the rosemary supernatant into a freeze drying bottle, and then put it into the cold trap of the freeze dryer. The temperature in the cold trap is -40°C and the freezing time is 8 hours. Reduce the pressure of the freeze dryer to a high vacuum state below 0.1 mbar, and dry in the high vacuum state for 24 hours. After freeze drying is completed, continue to maintain the high vacuum state for 2 hours, turn off the freeze dryer, slowly return to atmospheric pressure, open the freeze drying bottle, and collect the rosemary extract.

[0052] Step (2) includes the following process:

[0053] Q1. Material preparation: Wash the green tea leaves, and then put them into a 60℃ forced air drying oven to dry for 8 hours to obtain clean rosemary leaves;

[0054] Q2. Grinding and sieving: Grind the clean green tea leaves and pass them through a 60-mesh sieve to obtain green tea powder;

[0055] Q3. Extraction: Weigh green tea powder into a flask, add double distilled water, the solid-liquid ratio of green tea powder to double distilled water is 1:30, adjust pH to 5, perform shaking extraction in a 60°C water bath, repeat the extraction twice, centrifuge at 3000rpm for 5min, collect the supernatant to obtain the tea polyphenols extract.

[0056] Step (3) includes the following process:

[0057] K1. Prepare sodium alginate membrane liquid: weigh 2.1 g sodium alginate and 0.7 g polyacrylamide solid respectively, mix the sodium alginate and polyacrylamide, add 100 mL sterile deionized water, stir with a magnetic stirrer, set the speed to 350 rpm, set the temperature to 20°C, and stir for 20 min to obtain a sodium alginate membrane liquid;

[0058] K2. Preliminary cross-linking with calcium ions: Weigh 0.08 g of nano-calcium carbonate particles and add them to the sodium alginate membrane solution. Stir with a magnetic stirrer at a speed of 350 rpm, a temperature of 20°C, and a stirring time of 20 min to obtain a sodium alginate preliminary cross-linked membrane solution.

[0059] K3. Uniform cross-linking: Weigh 0.08 g of gluconolactone powder and add it to sodium alginate for preliminary cross-linking of the membrane liquid. Stir with a magnetic stirrer, set the speed to 350 rpm, set the temperature to 20°C, and stir for 50 min to obtain a sodium alginate cross-linked membrane liquid.

[0060] Step (4) includes the following process:

[0061] F1. Adding natural extract: Prepare the rosemary extract prepared above into a 3 mg / mL rosemary extract solution, take 2 mL and add it to the sodium alginate cross-linked membrane solution, then take 2 mL of tea polyphenols extract and add it to the sodium alginate cross-linked membrane solution to obtain a natural extract membrane solution with antioxidant and antibacterial functions;

[0062] F2. Film formation: The natural extract film liquid with antioxidant and antibacterial functions is homogenized with a high-speed homogenizer for 2 minutes, and ultrasonically defoamed for 12 minutes. 35 g of the film liquid is weighed and poured into an acrylic mold, and placed in a 20-25°C forced air dryer for water evaporation. The relative humidity is controlled at 50%. After 2-3 days, the packaging material of the natural extract with antioxidant and antibacterial functions is obtained.

[0063] Embodiment 2:

[0064] This embodiment provides a packaging material prepared from a natural extract having antioxidant and antibacterial functions, comprising the following steps:

[0065] (1) extracting rosemary extract with antioxidant and antibacterial functions from rosemary leaves;

[0066] (2) Extracting tea polyphenols with antioxidant and antibacterial properties from green tea;

[0067] (3) preparing a chitosan glacial acetic acid solution and a gelatin aqueous solution, mixing them to obtain a chitosan gelatin film solution;

[0068] (4) Rosemary extract and tea polyphenols are added to chitosan gelatin film liquid, and after drying, a natural extract packaging material with antioxidant and antibacterial functions is obtained.

[0069] Specifically, step (1) includes the following process:

[0070] S1. Material preparation: Wash the rosemary leaves, and then dry them in a drying oven at 62°C for 7 hours to obtain clean rosemary leaves;

[0071] S2, crushing and sieving: crushing the clean rosemary leaves and passing through an 80-mesh sieve to obtain rosemary leaf powder;

[0072] S3, ultrasonic extraction: weigh rosemary leaf powder, add 70% ethanol in a beaker, the solid-liquid ratio is 1:15, ultrasonicate at 50°C for 20min, ultrasonic power is 300W, and soak at room temperature for 18h to obtain rosemary extract;

[0073] S4, filtration and centrifugation: Filter the rosemary extract with gauze, centrifuge at 5000r / min for 15min, discard the precipitate, take the supernatant, and obtain rosemary supernatant;

[0074] S5. Freeze drying: pour the rosemary supernatant into a freeze drying bottle, and then put it into the cold trap of the freeze dryer. The temperature in the cold trap is -60°C and the freezing time is 10 hours. Reduce the pressure of the freeze dryer to a high vacuum state below 0.1 mbar, and dry in the high vacuum state for 26 hours. After freeze drying is completed, continue to maintain the high vacuum state for 3 hours, turn off the freeze dryer, slowly return to atmospheric pressure, open the freeze drying bottle, and collect the rosemary extract.

[0075] Step (2) includes the following process:

[0076] Q1. Material preparation: Wash the green tea leaves, and then put them into a 62℃ forced air drying oven to dry for 7 hours to obtain clean rosemary leaves;

[0077] Q2. Grinding and sieving: Grind the clean green tea leaves and pass them through an 80-mesh sieve to obtain green tea powder;

[0078] Q3. Extraction: Weigh green tea powder into a flask, add double distilled water, the solid-liquid ratio of green tea powder to double distilled water is 1:32, adjust pH to 6, perform shaking extraction in a 70°C water bath, repeat the extraction 3 times, centrifuge at 5000rpm for 10min, collect the supernatant to obtain the tea polyphenols extract.

[0079] Step (3) includes the following process:

[0080] K1. Prepare sodium alginate membrane liquid: weigh 4.5 g sodium alginate and 1.5 g polyacrylamide solid respectively, mix the sodium alginate and polyacrylamide, add 200 mL sterile deionized water, stir with a magnetic stirrer, set the speed to 400 rpm, set the temperature to 23°C, and stir for 25 min to obtain sodium alginate membrane liquid;

[0081] K2. Preliminary cross-linking with calcium ions: Weigh 0.18 g of nano calcium carbonate particles and add them to the sodium alginate membrane solution. Stir with a magnetic stirrer at a speed of 400 rpm, a temperature of 23°C, and a stirring time of 25 min to obtain a sodium alginate preliminary cross-linked membrane solution.

[0082] K3. Uniform cross-linking: Weigh 0.18 g of gluconolactone powder and add it to sodium alginate for preliminary cross-linking of the membrane liquid. Stir with a magnetic stirrer, set the speed to 400 rpm, set the temperature to 23°C, and stir for 55 min to obtain a sodium alginate cross-linked membrane liquid.

[0083] Step (4) includes the following process:

[0084] F1. Adding natural extract: Prepare the rosemary extract prepared above into a 4 mg / mL rosemary extract solution, take 9 mL and add it to the sodium alginate cross-linked membrane solution, then take 7 mL of tea polyphenols extract and add it to the sodium alginate cross-linked membrane solution to obtain a natural extract membrane solution with antioxidant and antibacterial functions;

[0085] F2. Film formation: The natural extract film liquid with antioxidant and antibacterial functions was homogenized with a high-speed homogenizer for 3 minutes, and ultrasonically defoamed for 16 minutes. 40 g of the film liquid was weighed and poured into an acrylic mold, and placed in a 23°C forced air dryer for water evaporation. The relative humidity was controlled at 50%. After 3 days, the packaging material of the natural extract with antioxidant and antibacterial functions was obtained.

[0086] Embodiment 3:

[0087] This embodiment provides a packaging material prepared from a natural extract having antioxidant and antibacterial functions, comprising the following steps:

[0088] (1) extracting rosemary extract with antioxidant and antibacterial functions from rosemary leaves;

[0089] (2) Extracting tea polyphenols with antioxidant and antibacterial properties from green tea;

[0090] (3) preparing a chitosan glacial acetic acid solution and a gelatin aqueous solution, mixing them to obtain a chitosan gelatin film solution;

[0091] (4) Rosemary extract and tea polyphenols are added to chitosan gelatin film liquid, and after drying, a natural extract packaging material with antioxidant and antibacterial functions is obtained.

[0092] Specifically, step (1) includes the following process:

[0093] S1. Material preparation: Wash the rosemary leaves, and then put them into a drying oven at 63°C for 7 hours to obtain clean rosemary leaves;

[0094] S2, crushing and sieving: crushing the clean rosemary leaves and passing through a 100-mesh sieve to obtain rosemary leaf powder;

[0095] S3, ultrasonic extraction: weigh rosemary leaf powder, add 70% ethanol in a beaker, the solid-liquid ratio is 1:20, ultrasonicate at 50°C for 40min, ultrasonic power is 300W, and soak at room temperature for 24h to obtain rosemary extract;

[0096] S4, filtration and centrifugation: Filter the rosemary extract with gauze, centrifuge at 5000r / min for 15min, discard the precipitate, take the supernatant, and obtain rosemary supernatant;

[0097] S5. Freeze drying: pour the rosemary supernatant into a freeze drying bottle, and then put it into the cold trap of the freeze dryer. The temperature in the cold trap is -80°C and the freezing time is 12 hours. Reduce the pressure of the freeze dryer to a high vacuum state below 0.1 mbar, and dry in the high vacuum state for 30 hours. After freeze drying is completed, continue to maintain the high vacuum state for 4 hours, turn off the freeze dryer, slowly return to atmospheric pressure, open the freeze drying bottle, and collect the rosemary extract.

[0098] Step (2) includes the following process:

[0099] Q1. Material preparation: Wash the green tea leaves, and then put them into a 63℃ forced air drying oven to dry for 7 hours to obtain clean rosemary leaves;

[0100] Q2. Grinding and sieving: Grind the clean green tea leaves and pass them through an 80-mesh sieve to obtain green tea powder;

[0101] Q3. Extraction: Weigh green tea powder into a flask, add double distilled water, the solid-liquid ratio of green tea powder to double distilled water is 1:30, adjust pH = 6, perform shaking extraction in a 70°C water bath, repeat the extraction 3 times, centrifuge at 5000rpm for 10min, collect the supernatant to obtain the tea polyphenols extract.

[0102] Step (3) includes the following process:

[0103] K1. Prepare sodium alginate membrane liquid: weigh 4.5 g sodium alginate and 1.5 g polyacrylamide solid respectively, mix the sodium alginate and polyacrylamide, add 200 mL sterile deionized water, stir with a magnetic stirrer, set the speed to 400 rpm, set the temperature to 23°C, and stir for 30 min to obtain sodium alginate membrane liquid;

[0104] K2. Preliminary cross-linking with calcium ions: Weigh 0.2 g of nano calcium carbonate particles and add them to the sodium alginate membrane solution. Stir with a magnetic stirrer at a speed of 450 rpm and a temperature of 25°C for 30 min to obtain a sodium alginate preliminary cross-linked membrane solution.

[0105] K3. Uniform cross-linking: Weigh 0.2 g of gluconolactone powder and add it to sodium alginate for preliminary cross-linking of the membrane liquid. Stir with a magnetic stirrer, set the speed to 450 rpm, set the temperature to 25°C, and stir for 60 min to obtain a sodium alginate cross-linked membrane liquid.

[0106] Step (4) includes the following process:

[0107] F1. Adding natural extract: Prepare the rosemary extract prepared above into a 5 mg / mL rosemary extract solution, take 7 mL and add it to the sodium alginate cross-linked membrane solution, then take 7 mL of tea polyphenols extract and add it to the sodium alginate cross-linked membrane solution to obtain a natural extract membrane solution with antioxidant and antibacterial functions;

[0108] F2. Film formation: The natural extract film liquid with antioxidant and antibacterial functions was homogenized with a high-speed homogenizer for 3 minutes, and ultrasonically defoamed for 16 minutes. 40 g of the film liquid was weighed and poured into an acrylic mold, and placed in a 25°C forced air dryer for water evaporation. The relative humidity was controlled at 50%. After 3 days, the packaging material of the natural extract with antioxidant and antibacterial functions was obtained.

[0109] Embodiment 4:

[0110] This embodiment provides a packaging material prepared from a natural extract having antioxidant and antibacterial functions, comprising the following steps:

[0111] (1) extracting rosemary extract with antioxidant and antibacterial functions from rosemary leaves;

[0112] (2) Extracting tea polyphenols with antioxidant and antibacterial properties from green tea;

[0113] (3) preparing a chitosan glacial acetic acid solution and a gelatin aqueous solution, mixing them to obtain a chitosan gelatin film solution;

[0114] (4) Rosemary extract and tea polyphenols are added to chitosan gelatin film liquid, and after drying, a natural extract packaging material with antioxidant and antibacterial functions is obtained.

[0115] Specifically, step (1) includes the following process:

[0116] S1. Material preparation: wash the rosemary leaves, and then put them into a drying oven at 65°C for 6 hours to obtain clean rosemary leaves;

[0117] S2, crushing and sieving: crushing the clean rosemary leaves and passing through a 120-mesh sieve to obtain rosemary leaf powder;

[0118] S3, ultrasonic extraction: weigh rosemary leaf powder, add 98% ethanol in a beaker, the solid-liquid ratio is 1:25, ultrasonicate at 60°C for 50min, ultrasonic power is 400W, and soak at room temperature for 24h to obtain rosemary extract;

[0119] S4, filtration and centrifugation: Filter the rosemary extract with gauze, centrifuge at 5000r / min for 15min, discard the precipitate, take the supernatant, and obtain rosemary supernatant;

[0120] S5. Freeze drying: pour the rosemary supernatant into a freeze drying bottle, and then put it into the cold trap of the freeze dryer. The temperature in the cold trap is -80°C and the freezing time is 12 hours. Reduce the pressure of the freeze dryer to a high vacuum state below 0.1 mbar, and dry in the high vacuum state for 30 hours. After freeze drying is completed, continue to maintain the high vacuum state for 4 hours, turn off the freeze dryer, slowly return to atmospheric pressure, open the freeze drying bottle, and collect the rosemary extract.

[0121] Step (2) includes the following process:

[0122] Q1. Material preparation: Wash the green tea leaves, and then put them into a 65℃ forced air drying oven to dry for 6 hours to obtain clean rosemary leaves;

[0123] Q2. Grinding and sieving: Grind the clean green tea leaves and pass them through a 100-mesh sieve to obtain green tea powder;

[0124] Q3. Double distillation extraction: Weigh green tea powder into a flask, add double distilled water, the solid-liquid ratio of green tea powder to double distilled water is 1:35, adjust pH = 6, perform shaking extraction in an 80°C water bath, repeat the extraction 3 times, centrifuge at 5000rpm for 10min, collect the supernatant to obtain the tea polyphenols extract.

[0125] Step (3) includes the following process:

[0126] K1. Prepare sodium alginate membrane liquid: weigh 4.8 g sodium alginate and 0.16 g polyacrylamide solid respectively, mix the sodium alginate and polyacrylamide, add 200 mL sterile deionized water, stir with a magnetic stirrer, set the speed to 450 rpm, set the temperature to 25°C, and stir for 30 min to obtain a sodium alginate membrane liquid;

[0127] K2. Preliminary cross-linking with calcium ions: Weigh 0.24 g of nano calcium carbonate particles and add them to the sodium alginate membrane solution. Stir with a magnetic stirrer at a speed of 450 rpm and a temperature of 25°C for 30 min to obtain a sodium alginate preliminary cross-linked membrane solution.

[0128] K3. Uniform cross-linking: Weigh 0.24 g of gluconolactone powder and add it to sodium alginate for preliminary cross-linking of the membrane liquid. Stir with a magnetic stirrer, set the speed to 450 rpm, set the temperature to 25°C, and stir for 60 min to obtain a sodium alginate cross-linked membrane liquid.

[0129] Step (4) includes the following process:

[0130] F1. Adding natural extract: Prepare the rosemary extract prepared above into a 5 mg / mL rosemary extract solution, take 8 mL and add it to the sodium alginate cross-linked membrane solution, then take 8 mL of tea polyphenols extract and add it to the sodium alginate cross-linked membrane solution to obtain a natural extract membrane solution with antioxidant and antibacterial functions;

[0131] F2. Film formation: The natural extract film liquid with antioxidant and antibacterial functions was homogenized with a high-speed homogenizer for 3 minutes, and ultrasonically defoamed for 16 minutes. 40 g of the film liquid was weighed and poured into an acrylic mold, and placed in a 25°C forced air dryer for water evaporation. The relative humidity was controlled at 50%. After 3 days, the packaging material of the natural extract with antioxidant and antibacterial functions was obtained.

[0132] Comparative Example 1:

[0133] Comparative Example 1 Compared with Example 3, in the preparation of the packaging material of the natural extract with antioxidant and antibacterial functions in Comparative Example 1, no gluconolactone was added, and other conditions remained unchanged.

[0134] Comparative Example 2:

[0135] Comparative Example 2 Compared with Example 3, in Comparative Example 2, when preparing the packaging material of the natural extract with antioxidant and antibacterial functions, only an equal amount of tea polyphenol extract solution was added, and no rosemary extract solution was added, and other conditions remained unchanged.

[0136] Comparative Example 3:

[0137] Comparative Example 3 Compared with Example 3, in Comparative Example 3, when preparing the packaging material of the natural extract with antioxidant and antibacterial functions, only an equal amount of rosemary extract solution was added, and no tea polyphenol extract solution was added, and other conditions remained unchanged.

[0138] Comparative Example 4:

[0139] Comparative Example 4 Compared with Example 3, in Comparative Example 4, when preparing the packaging material of the natural extract with antioxidant and antibacterial functions, sterile water was used to replace the rosemary extract solution and the tea polyphenol extract solution, and other conditions remained unchanged.

[0140] Experimental example

[0141] The performance of the packaging materials of the natural extracts with antioxidant and antibacterial functions prepared in Examples 1-4 and Comparative Examples 1-4 was monitored.

[0142] 1. Determination of tensile strength and elongation at break

[0143] Select smooth and undamaged composite membranes and cut them into regular strips of 30mm×20mm. Fix them vertically and flatly on the electronic dynamometer of the tensile meter. The initial spacing is 50mm and the stretching rate is 20mm / min. Make 3 parallels for each group of composite membranes and record the maximum tensile strength and displacement when the membrane breaks. Among them, the tensile strength calculation formula is:

[0144]

[0145] Wherein, T is the tensile strength (MPa); F is the maximum tensile force when the film breaks (N); L is the average thickness of the film (mm); W is the width of the film sample (mm).

[0146] The calculation is based on the maximum tensile force corresponding to the displacement when measuring the tensile strength. The elongation at break is calculated by the formula:

[0147]

[0148] Wherein, E is the elongation at break (%); L0 is the length of the film before stretching (mm); L1 is the length of the film after stretching (mm). The results of tensile strength and elongation at break are shown in Table 1:

[0149] Table 1

[0150]

[0151]

[0152] As can be seen from the results of the measurement in Table 1, the packaging materials of the natural extracts with antioxidant and antibacterial functions prepared in Examples 1-4 of the present invention have excellent mechanical properties. By comparing Comparative Example 1 with Examples 1-4, it can be seen that the addition of gluconolactone as a pH regulator can significantly improve its tensile strength and elongation at break, because gluconolactone slowly releases nano calcium carbonate, makes the cross-linking of sodium alginate more uniform, and makes the membrane liquid more delicate. The prepared packaging material has a consistent thickness, is evenly stressed and is not easy to break; By comparing Comparative Examples 2-4 with Examples 1-4, it can be seen that the addition of rosemary extract and tea polyphenols with antioxidant properties extracted by the present invention can also improve its tensile strength and elongation at break, because the added rosemary extract and tea polyphenols make the membrane liquid system more dispersed, and closely combine with the sodium alginate cross-linked membrane liquid by hydrogen bond interaction, and fully fill the gaps therein during the film forming process.

[0153] 2. Water vapor permeability

[0154] Water vapor permeability is measured by gravimetric method using a water vapor permeability tester. The test cup is 30mm in diameter and filled with sterile deionized water. The sample is then sealed on the test cup and placed in a controlled room at 25°C and 50% relative humidity. The weight of the test cup is recorded every 15 minutes for 24 hours. The water vapor transmission rate (WVP) of the sample is calculated by the following formula:

[0155]

[0156] Where Δm is the weight gain (g), d is the membrane thickness (cm), and A is the membrane permeation area (m 2 ), t is the time interval (h), Δp is the water vapor pressure difference on both sides of the film sample (kPa). The water vapor transmission rate measurement results are shown in Table 2:

[0157] Table 2

[0158] sample <![CDATA[Water vapor transmission rate (g*cm / m 2 *h*kPa)]]> Example 1 0.70 Example 2 0.79 Example 3 0.63 Example 4 0.72 Comparative Example 1 9.32 Comparative Example 2 1.02 Comparative Example 3 1.01 Comparative Example 4 1.32

[0159] It can be seen from the results of Table 2 that the packaging materials of the natural extracts with antioxidant and antibacterial functions prepared in Examples 1-4 of the present invention have excellent moisture barrier properties. By comparing Comparative Example 1 with Examples 1-4, it can be seen that the addition of gluconolactone as a pH regulator can significantly improve its moisture barrier properties. The reason is that gluconolactone slowly releases nano-calcium carbonate, making the cross-linking of sodium alginate more uniform, and the prepared packaging material is more compact, and water vapor is not easy to pass through; by comparing Comparative Examples 2-4 with Examples 1-4, it can be seen that the addition of rosemary extract and tea polyphenols with antioxidant properties extracted by the present invention can also improve its moisture barrier properties. The reason may be that the added rosemary extract and tea polyphenols make the membrane liquid system more dispersed, and closely combine with the sodium alginate cross-linked membrane liquid through hydrogen bond interaction, and fully fill the gaps therein during the film formation process.

[0160] 3. Antioxidant Determination

[0161] The antioxidant property of the packaging material was tested by DPPH free radical scavenging activity. 1 mL of the packaging material samples of the natural extracts with antioxidant and antibacterial functions prepared in Examples 1-4 and Comparative Examples 1-4 were added to 4.0 mL of DPPH solution to ensure uniform mixing. The mixed solution was placed at room temperature for reaction for 30 minutes. The absorbance of the mixed solution was measured at a wavelength of 517 nm using a spectrophotometer. The DPPH free radical scavenging rate was calculated using the following formula:

[0162]

[0163] Among them, A 样品 is the absorbance of the solution after adding the antioxidant, A 对照is the absorbance of the DPPH solution without adding antioxidant. The DPPH free radical scavenging test results of the packaging material prepared above are determined according to the formula. Figure 1 As shown, the packaging materials of the natural extracts with antioxidant and antibacterial functions prepared in Examples 1-4 of the present invention have significant antioxidant properties. By comparing Comparative Examples 2-4 with Examples 1-4, it can be seen that adding the rosemary extract with antioxidant properties and tea polyphenols extracted by the present invention can significantly improve its antioxidant properties.

[0164] 4. Determination of antibacterial performance

[0165] The antibacterial properties of the packaging material prepared above were determined by the agar diffusion method. Two bacteria were selected to determine their antibacterial properties. The antibacterial activities of Escherichia coli (E. coli, ATCC25922) and Staphylococcus aureus (S. aureus, ATCC25923) were determined. 100 μL of bacterial suspension (about 10 7 CFU / mL) was evenly coated on the surface of the solid culture medium, and the Oxford cup was picked up with tweezers and placed on the culture medium. 200 μL of membrane solution (diameter 8 mm) was injected respectively, and the cells were placed in a 37°C incubator for 12 hours. Finally, the size of the inhibition zone formed around the Oxford cup was measured. The measurement results are shown in Table 3:

[0166] Table 3

[0167]

[0168]

[0169] The packaging materials of the natural extracts with antioxidant and antibacterial functions prepared in Examples 1-4 of the present invention have significant antibacterial properties. By comparing Comparative Examples 2-4 with Examples 1-4, it can be seen that adding the rosemary extract with antioxidant properties and tea polyphenols extracted by the present invention can significantly improve its antibacterial properties.

[0170] V. Determination of freshness preservation performance

[0171] The cut apples were placed in a beaker and sealed with the above-prepared packaging material. The unsealed apples were set as the control group and stored at room temperature (25±2°C, 75% relative humidity). During the storage process, the weight of the fruit was recorded every day and the rotten area of ​​the apples was measured. The weight loss rate and rotten rate of the apples were used as the evaluation indicators to determine the fresh-keeping performance of the packaging material prepared in the embodiment of the present invention. The measurement results are shown in Table 4:

[0172] Table 4

[0173]

[0174] As can be seen from the results of Table 4, the packaging materials of the natural extracts with antioxidant and antibacterial functions prepared in Examples 1-4 of the present invention have excellent preservation performance. By comparing Comparative Example 1 with Examples 1-4, it can be seen that without adding gluconolactone as a pH regulator, the preservation performance will be reduced; by comparing Comparative Examples 2-4 with Examples 1-4, it can be seen that adding the rosemary extract with antioxidant properties and tea polyphenols extracted by the present invention can significantly improve the preservation performance, because compared with the unsealed control group, the packaging material prepared by the present invention can not only isolate a part of the external microbial contamination, but also exert antioxidant and antibacterial properties, thereby improving the preservation performance of food.

[0175] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0176] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A packaging material prepared from a natural extract having antioxidant and antibacterial functions, characterized in that: The method for preparing the packaging material comprises the following steps: (1) extracting rosemary extract with antioxidant and antibacterial functions from rosemary leaves; (2) Extracting tea polyphenols with antioxidant and antibacterial properties from green tea; (3) preparing a chitosan glacial acetic acid solution and a gelatin aqueous solution, mixing them to obtain a chitosan gelatin film solution; (4) Rosemary extract and tea polyphenols are added to chitosan gelatin film liquid, and after drying, a natural extract packaging material with antioxidant and antibacterial functions is obtained.

2. The packaging material prepared from a natural extract having antioxidant and antibacterial functions according to claim 1, characterized in that: Step (1) includes the following process: S1. Material preparation: wash the rosemary leaves, and then put them into a drying oven to dry them to obtain clean rosemary leaves; S2, crushing and sieving: crushing the clean rosemary leaves and sieving them to obtain rosemary leaf powder; S3, ultrasonic extraction: Weigh rosemary leaf powder, add ethanol in a beaker, put it into ultrasonic extraction, and soak at room temperature to obtain rosemary extract; S4, filtration and centrifugation: filtering the rosemary extract, centrifuging, discarding the precipitate, taking the supernatant, and obtaining a rosemary supernatant; S5. Freeze drying: pour the rosemary supernatant into a freeze drying bottle, then put it into the cold trap of a freeze dryer, reduce the pressure of the freeze dryer to a high vacuum state, and dry; after drying, continue to maintain the high vacuum state; after freeze drying, turn off the freeze dryer and slowly return to atmospheric pressure; open the freeze drying bottle and collect the rosemary extract.

3. The packaging material prepared from a natural extract having antioxidant and antibacterial functions according to claim 2, characterized in that: During the preparation of S1 materials, the materials are dried in a drying oven at 60 to 65°C for 6 to 8 hours; during the crushing and screening of S2 materials, the materials are sieved through a 60 to 120 mesh sieve; S3 uses 60 to 98% ethanol, the solid-liquid ratio is 1:10 to 25, ultrasonic treatment is performed at 40 to 60°C for 10 to 50 minutes, the ultrasonic power is 200 to 400W, and the materials are soaked at room temperature for 16 to 24 hours; S4 rosemary extract is filtered through gauze, and centrifuged at 3000 to 5000 r / min for 10 to 15 minutes; the temperature in the freeze-drying cold trap of S5 is -40 to -80°C, the freezing time is 8 to 12 hours, and a high vacuum state is obtained when the temperature is below 0.1 mbar, the materials are dried in the high vacuum state for 24 to 30 hours, and the high vacuum state is maintained for 2 to 4 hours.

4. The packaging material prepared from a natural extract having antioxidant and antibacterial functions according to claim 1, characterized in that: Step (2) includes the following process: Q1. Material preparation: Wash the green tea leaves and then put them in a drying oven to dry them to obtain clean green tea leaves; Q2. Grinding and sieving: Grind the clean green tea leaves and sieve them to get green tea powder; Q3. Extraction: Weigh green tea powder into a flask, add double distilled water, adjust the pH, set the temperature and perform shaking extraction in a water bath, repeat the extraction, centrifuge, and collect the supernatant to obtain the tea polyphenols extract.

5. The packaging material prepared from a natural extract having antioxidant and antibacterial functions according to claim 4, characterized in that: Q1 drying is placed in a 60-65°C forced air drying oven for 6-8 hours; Q2 green tea leaves are crushed and sieved through a 60-100 mesh sieve; Q3 extraction of green tea powder and double distilled water with a material-liquid ratio of 1:30-35; pH is adjusted to 5-6; water bath temperature is 60-80°C; water bath time is 40-50 minutes; stirring rate is 50-200 r / min; extraction is repeated 2-3 times; centrifugation is performed at 3000-5000 rpm for 5-10 minutes.

6. The packaging material prepared from a natural extract having antioxidant and antibacterial functions according to claim 1, characterized in that: Step (3) includes the following process: K1. Prepare sodium alginate membrane liquid: weigh sodium alginate and polyacrylamide solids respectively, mix the sodium alginate and polyacrylamide, add sterile deionized water, and mix evenly with a magnetic stirrer to obtain a sodium alginate membrane liquid; K2. Preliminary cross-linking with calcium ions: weigh nano-calcium carbonate particles and add them to the sodium alginate membrane solution, and stir them thoroughly with a magnetic stirrer to obtain a sodium alginate preliminary cross-linked membrane solution; K3. Uniform cross-linking: Weigh gluconolactone powder and add it to sodium alginate to initially cross-link the membrane liquid, and continue to stir it fully with a magnetic stirrer to obtain a sodium alginate cross-linked membrane liquid.

7. The packaging material prepared from a natural extract having antioxidant and antibacterial functions according to claim 6, characterized in that: The sodium alginate and polyacrylamide are mixed in a mass ratio of 3:1, the speed of the magnetic stirrer is 350-450 rpm, the temperature is set at 20-25°C, the stirring time is 20-30 min, and the mass concentration of the sodium alginate membrane liquid is 2.8-3.2%; the content of the nano calcium carbonate particles in the sodium alginate membrane liquid is 0.08-0.12%, the speed of the magnetic stirrer is 350-450 rpm, the temperature is set at 20-25°C, and the stirring time is 20-30 min; the content of the gluconolactone powder in the sodium alginate cross-linked membrane liquid is 0.08-0.12%, the speed of the magnetic stirrer is 350-450 rpm, the temperature is set at 20-25°C, and the stirring time is 50-60 min.

8. The packaging material prepared from a natural extract having antioxidant and antibacterial functions according to claim 1, characterized in that: Step (4) includes the following process: F1. Adding natural extracts: The rosemary extract prepared above is prepared into a rosemary extract solution and added into a sodium alginate cross-linked membrane liquid, and then the tea polyphenols extract is added into the sodium alginate cross-linked membrane liquid to obtain a natural extract membrane liquid with antioxidant and antibacterial functions; F2. Film formation: The natural extract film liquid with antioxidant and antibacterial functions is homogenized by a high-speed homogenizer, ultrasonically defoamed, weighed and poured into an acrylic mold, and placed in a blast dryer to evaporate water, thereby obtaining a packaging material of the natural extract with antioxidant and antibacterial functions.

9. The packaging material prepared from a natural extract having antioxidant and antibacterial functions according to claim 8, characterized in that: The concentration of the rosemary extract solution is 3-5 mg / mL, the volume ratio of the rosemary extract solution to the sodium alginate cross-linked membrane liquid is 1:16-30, and the volume ratio of the tea polyphenol extract solution to the sodium alginate cross-linked membrane liquid is 1:16-30; the high-speed homogenizer is homogenized for 2-3 minutes, and the ultrasonic defoaming is performed for 12-16 minutes; 35-40 g of the natural extract membrane liquid with antioxidant and antibacterial functions is weighed and placed in a 20-25° C. air drier for drying for 2-3 days, and the relative humidity is 50%.

10. Use of a packaging material prepared from the natural extract with antioxidant and antibacterial functions according to any one of claims 1 to 9 in food packaging.

Images