A green cauliflower fresh-keeping paper, a preparation method and application thereof

Abstract

The present application relates to green flower vegetable fresh-keeping paper and preparation method and application, including paper-like carrier, and further including powder-like Pickering emulsion freeze-dried sprayed on the carrier, components of the Pickering emulsion freeze-dried include 1-MCP, mustard essential oil, emulsifier and stabilizer.The green flower vegetable fresh-keeping paper has the effects of antibacterial, green protection, insecticidal and antioxidant on green flower vegetable, can realize long-acting fresh-keeping of green flower vegetable during storage, is suitable for large-scale popularization and application, is convenient for packaging and storage of large quantities of postharvest green flower vegetable, and raw materials are widely sourced, low in price, suitable for large-scale production and use, and the related raw materials are non-toxic and harmless to human body and environment, safe and reliable.

Description

Technical Field

[0001] This invention relates to the field of fruit and vegetable preservation technology, and in particular to a broccoli preservation paper, its preparation method, and its application. Background Technology

[0002] Broccoli, also known as brassica oleracea, is a cruciferous vegetable and a common vegetable on the dining table. Currently, my country produces approximately 2.45 million tons of broccoli annually, ranking first in the world in terms of cultivation. Broccoli is a climacteric fruit, meaning it ripens and ages rapidly through the release of ethylene. During storage and transportation, broccoli experiences vigorous postharvest respiration and transpiration, leading to rapid metabolism and degradation of nutrients within its cells. This results in reduced nutritional value and deterioration, such as dehydration and yellowing. Oxidation also causes the loss of vitamin C, amino acids, glucose, and other flavorful nutrients, affecting its taste. Furthermore, broccoli is susceptible to infection by various bacteria and fungi, leading to spoilage and food safety issues. In addition, insect pests can cause holes on the surface of broccoli, exacerbating microbial contamination.

[0003] To slow down the ripening and aging process of broccoli, the commonly used preservative is 1-methylcyclopropene (1-MCP), which can bind to ethylene acceptors in broccoli, thereby inhibiting the ripening effect of ethylene. However, 1-MCP does not have antibacterial or antioxidant functions, and therefore cannot prevent quality deterioration caused by oxidation and microorganisms.

[0004] Furthermore, food preservation paper is a type of food packaging product. It is made by adsorbing preservatives onto a highly absorbent material and then bonding it to paper with an adhesive. For example, Chinese invention patents with application number CN202310634914.2 (publication number CN116556109A) and application number CN202210985375.2 (publication number CN115491926A) disclose existing food preservation papers. However, no food preservation paper suitable for broccoli has been reported so far, mainly because a suitable preservative for broccoli has not yet been found. Summary of the Invention

[0005] The first technical problem to be solved by the present invention is to provide a broccoli preservation paper that is suitable for broccoli and has a good preservation effect, in contrast to the prior art.

[0006] The second technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned broccoli preservation paper in light of the prior art.

[0007] The third technical problem to be solved by the present invention is to provide an application of the above-mentioned broccoli preservation paper in light of the prior art.

[0008] The technical solution adopted by the present invention to solve the first technical problem mentioned above is: a broccoli preservation paper, comprising a paper-like carrier, characterized in that it further comprises a powdered Pickering emulsion freeze-dried on the carrier, wherein the components of the Pickering emulsion freeze-dried include 1-MCP, mustard oil, emulsifier and stabilizer.

[0009] Furthermore, the emulsifier includes collagen. Collagen, as an emulsifier, facilitates the formation of a Pickering emulsion system between 1-MCP and mustard oil.

[0010] Furthermore, the stabilizer includes chitosan and natural anthocyanins. Chitosan contains a large number of hydrophilic groups such as hydrophilic hydroxyl and amino groups, which, when combined with mustard oil, form a Pickering emulsion. Natural anthocyanins, on the one hand, can bind with chitosan in the Pickering emulsion via hydrogen bonds, thereby enhancing the stability of the emulsion system; on the other hand, they possess strong antioxidant activity, protecting the mustard oil and preventing the volatile substances in the mustard oil from premature oxidation and loss of efficacy during use.

[0011] Furthermore, the carrier is absorbent paper. Powdered Pickering emulsion can be freeze-dried and adsorbed onto the absorbent paper using electrostatic force.

[0012] The technical solution adopted to further solve the second technical problem mentioned above is: a method for preparing broccoli preservation paper as described above, characterized by including the following steps:

[0013] (1) Mix 1-MCP and mustard oil at a concentration of 0.5%-1.0% (m / v), shake the mixture to dissolve it completely, and obtain a 1-MCP mustard oil solution;

[0014] (2) Take the 1-MCP mustard oil solution and collagen obtained in step (1) and add them to deionized water at a ratio of 2%-5% (v / v) and 3%-6% (m / v) respectively to obtain a mixture. Under low temperature conditions, the mixture is ultrasonically emulsified to obtain an emulsion.

[0015] (3) Glacial acetic acid and glycerol were added separately to fresh deionized water to obtain a deionized aqueous solution, wherein the concentrations of the glacial acetic acid and glycerol in the deionized aqueous solution were 0.2% (v / v) and 50% (m / v), respectively. Unlike chitosan and natural anthocyanins, glacial acetic acid and glycerol are stabilizers after the Pickering emulsion system is formed, which can effectively prevent the Pickering emulsion from denaturing during subsequent pre-freezing and freeze-drying processes.

[0016] Chitosan nanoparticles and natural anthocyanins were added to the above deionized solution in proportions of 3%-5% (m / v) and 4%-6% (m / v), respectively. Then, the mixture was homogenized at high speed. Finally, the emulsion obtained in step (2) was added to the deionized aqueous solution and stirred thoroughly at room temperature to obtain Pickering emulsion.

[0017] (4) The Pickering emulsion from step (3) is pre-frozen at -20°C for 12 hours, and then freeze-dried under vacuum for 24 to 36 hours until all the water is removed to obtain freeze-dried Pickering emulsion. After spray drying, the freeze-dried Pickering emulsion is in powder form. The pre-freezing operation enables the water in the Pickering emulsion to form crystals that are conducive to sublimation, thereby ensuring the effect of vacuum freeze-drying.

[0018] (5) Using electrostatic spraying, the powdered Pickering emulsion is freeze-dried and evenly sprayed onto the surface of the carrier. Another identical carrier is attached to the side of the carrier with powder. The two carriers are then bonded together around the edges using an adhesive to obtain broccoli preservation paper.

[0019] The technical solution adopted to further solve the third technical problem mentioned above is: an application of the broccoli preservation paper as described above, characterized in that, when in use, the broccoli preservation paper is laid flat on the surface of the broccoli, and then the broccoli and the broccoli preservation paper are sealed and stored together.

[0020] Furthermore, the amount of broccoli preservation paper used is 10-15 kg / sheet, and the area of ​​each broccoli preservation paper is 30cm×40cm.

[0021] Compared with existing technologies, the advantages of this invention are as follows: In this invention, the powdered Pickering emulsion is freeze-dried and adsorbed onto a paper-like carrier using electrostatic force. The components of the freeze-dried Pickering emulsion include 1-MCP, mustard oil, emulsifier, and stabilizer. Mustard oil, as a solvent for 1-MCP, works synergistically with 1-MCP to preserve freshness, achieving antibacterial, green-protecting, insecticidal, and antioxidant effects. Furthermore, the use of a stable Pickering emulsion as the encapsulation system for 1-MCP and mustard oil solves the drawback of high volatility of mustard oil, preventing rapid evaporation and inactivation of 1-MCP and mustard oil during use. This allows for the slow release of 1-MCP and mustard oil, thus achieving a long-lasting preservation effect during the storage of broccoli. Furthermore, in this invention, the Pickering emulsion is freeze-dried and uniformly adsorbed onto the carrier in powder form, which increases the contact area between the Pickering emulsion powder and the ambient gas, thereby facilitating the release of 1-MCP and mustard oil in the Pickering emulsion powder and improving the uniformity of release. At the same time, it is easier to operate in actual use, suitable for large-scale promotion and application, and convenient for the packaging and storage of large quantities of broccoli after harvest.

[0022] Furthermore, the raw materials used in this invention, such as 1-MCP and mustard oil, are widely available and inexpensive, making them suitable for large-scale production. Moreover, all of these raw materials are non-toxic to humans and the environment, ensuring safety. In addition, the preservation paper in this invention is stable, does not damage the packaging, facilitates long-term preservation, and has broad application prospects. Attached Figure Description

[0023] Figure 1 The changes in the appearance of broccoli during storage in Example 3 of this invention;

[0024] Figure 2 The changes in sensory scores of broccoli during storage in Example 3 of this invention;

[0025] Figure 3 This refers to the change in the relative conductivity of broccoli during storage in Example 3 of the present invention.

[0026] Figure 4 This refers to the change in chlorophyll content of broccoli leaves during storage in Example 3 of the present invention;

[0027] Figure 5 This refers to the change in malondialdehyde content in broccoli during storage in Example 3 of the present invention;

[0028] Figure 6 This refers to the changes in the total phenolic and total flavonoid content of broccoli during storage in Example 3 of the present invention. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0030] Example 1: Preparation of broccoli preservation paper

[0031] (1) Mix 0.5g of 1-MCP (α-cyclodextrin inclusion complex) and 100mL of mustard oil (purity 99%, Jiangxi Fanglin Fragrance Co., Ltd., the same below) at 0.5% (m / v) and shake the mixture on a shaker at 1400rpm for 1h to dissolve it completely.

[0032] (2) Take 20 mL of the 1-MCP mustard oil solution obtained in step (1) and 30 g of collagen (purity 90%, Henan Kangguan Biotechnology Co., Ltd., the same below) and add them to 1000 mL of deionized water at a ratio of 2% (v / v) and 3% (m / v) respectively to obtain a mixture. Use an ultrasonic crusher to ultrasonically emulsify the mixture for 5 min under ice water bath conditions with a power of 800W to obtain an emulsion.

[0033] (3) Add 2 mL of glacial acetic acid and 500 g of glycerol to 1000 mL of fresh deionized water. Then add 30 g of chitosan nanoparticles and 40 g of natural anthocyanins (purity 95%, Shaanxi Zelang Biotechnology, the same below) to the deionized water in sequence. Then homogenize at 8000 rpm for 5 min using a high-speed homogenizer. Finally, add the emulsion obtained in step (2) to the deionized water and stir continuously at room temperature for 1 h to obtain Pickering emulsion.

[0034] (4) The Pickering emulsion from step (3) is pre-frozen at -20°C for 12 hours (in this embodiment, a refrigerator is used for pre-freezing), and then vacuum freeze-dried for 24 hours until all moisture is removed to obtain freeze-dried Pickering emulsion. After spray drying, the freeze-dried Pickering emulsion is in powder form.

[0035] (5) Collect the powder produced by spray drying, and evenly spray the powder onto the surface of absorbent paper (30cm×40cm) using electrostatic spraying. The powder can adhere to the absorbent paper by electrostatic force. The spraying amount is 0.1g / cm. 2 .

[0036] (6) Attach the same absorbent paper to the powdery surface of the absorbent paper, and use adhesive to glue the absorbent paper around the edges to make broccoli preservation paper.

[0037] Example 2: Preparation of broccoli preservation paper

[0038] (1) Mix 1.0 g of 1-MCP (α-cyclodextrin inclusion complex) and 100 mL of mustard oil at a concentration of 1.0% (m / v) and shake the mixture on a shaker at 1400 rpm for 1 h to dissolve it completely.

[0039] (2) Take 50 mL of the 1-MCP mustard oil solution obtained in step (1) and 60 g of collagen and add them to 1000 mL of deionized water at a ratio of 5% (v / v) and 6% (m / v) respectively to obtain a mixture. Use an ultrasonic crusher to ultrasonically emulsify the mixture for 5 min under ice water bath conditions at a power of 1000 W to obtain an emulsion.

[0040] (3) Add 2 mL of glacial acetic acid and 500 g of glycerol to 1000 mL of fresh deionized water. Then add 50 g of chitosan nanoparticles and 60 g of natural anthocyanins to the deionized water. Then homogenize the mixture at 8000 rpm for 5 min using a high-speed homogenizer. Finally, add the emulsion obtained in step (2) to the deionized water and stir continuously at room temperature for 1 h to obtain Pickering emulsion.

[0041] (4) The Pickering emulsion from step (3) is pre-frozen at -20°C for 12 hours (in this embodiment, a refrigerator is used for pre-freezing), and then vacuum freeze-dried for 36 hours until all moisture is removed to obtain freeze-dried Pickering emulsion. After spray drying, the freeze-dried Pickering emulsion is in powder form.

[0042] (5) Collect the powder produced by spray drying, and evenly spray the powder onto the surface of absorbent paper (30cm×40cm) using electrostatic spraying. The powder can adhere to the absorbent paper by electrostatic force. The spraying amount is 0.2g / cm. 2 .

[0043] (6) Attach the same absorbent paper to the powdery surface of the absorbent paper, and use adhesive to glue the absorbent paper around the edges to make broccoli preservation paper.

[0044] Example 3: Storage Test

[0045] The broccoli preservation paper prepared in Example 1 was used at a ratio of one sheet per 10 kg of broccoli. It was laid flat on the surface of the broccoli and then packaged in PVC plastic bags (broccoli preservation paper treatment, 1-MCP+MEO). The packaged broccoli was then placed in plastic baskets and stored at 4°C. Meanwhile, untreated broccoli, broccoli treated with 1-MCP, and broccoli treated with freeze-dried mustard oil emulsion powder (MEO) served as control groups.

[0046] Sensory properties, electrical conductivity, and chlorophyll content of broccoli were tested during storage, and the results are as follows: Figure 1 and Figure 2 As shown. By Figure 1 and Figure 2 It is evident that after 21 days of storage, the broccoli in the control group showed yellowing and mold growth, which worsened on day 28, producing an off-odor. Broccoli treated with MEO under postharvest conditions showed yellowing after 21 days; however, broccoli treated with 1-MCP preservative did not show yellowing compared to the control group, although mold spots did form. This is because 1-MCP is an effective inhibitor of ethylene and can irreversibly interact with its receptor, thus delaying fruit and vegetable ripening but not having antibacterial function. Broccoli treated with 1-MCP+MEO did not show yellowing or mold growth during the 28-day storage period (e.g., Figure 1 As shown), and the highest sensory rating (e.g.) Figure 2 As shown in the image, this method provides the best preservation effect.

[0047] Furthermore, relative conductivity, by measuring cell membrane permeability, reflects the integrity of the cell membrane and can indicate the degree of cell damage and the senescence of vegetables. For example... Figure 3 As shown, all three preservation treatment groups (1-MCP+MEO, 1-MCP, and MEO) in this invention inhibited the increase in relative conductivity of broccoli, and showed significant differences compared to the control group, indicating that the preservative treatment could significantly inhibit the increase in relative conductivity. In the early stage of storage, the relative conductivity of broccoli treated with MEO increased significantly, possibly because the active ingredients in the essential oil caused some damage to the cell membrane during the antibacterial process, leading to cell fluid leakage and thus increasing relative conductivity. The 1-MCP preservative treatment showed the smallest increase during storage from 7 to 21 days, showing a significant difference compared to other treatment groups (P<0.05). At 28 days of storage, the broccoli treated with 1-MCP+MEO had the lowest relative conductivity, indicating that the synergistic preservation treatment of 1-MCP and mustard essential oil effectively maintained cell integrity.

[0048] Furthermore, chlorophyll content is one of the key indicators for evaluating the quality of post-harvest broccoli, and also an important indicator for assessing the nutritional value of vegetables. For example... Figure 4As shown, in this invention, on the 14th day of storage, the control group showed the largest decrease in chlorophyll content, reaching 33 mg / 100g, which was 46.42% of the initial value. This was significantly different from the chlorophyll content in the broccoli treated with preservatives (1-MCP+MEO, 1-MCP, MEO) (P<0.05), indicating that preservative treatment can effectively control the decrease in chlorophyll content. Among them, the 1-MCP+MEO treatment group showed the smallest decrease in chlorophyll content because 1-MCP inhibited broccoli maturation and MEO inhibited microbial reproduction and maintained cell membrane integrity, resulting in a significant difference compared to other treatment groups (1-MCP, MEO) (P<0.05). Therefore, the 1-MCP+MEO treatment can better inhibit the decrease in chlorophyll content in broccoli.

[0049] Furthermore, MDA (malondialdehyde) is an important product of membrane lipid peroxidation. The accumulation of MDA can lead to damage to the cell membrane and organelles, and can reflect the aging of plant tissues and the level of cell membrane lipid peroxidation. For example... Figure 5 As shown, in the later stage of storage in this invention, the malondialdehyde (MDA) content of broccoli treated with 1-MCP+MEO was 9.1 μmol / g, significantly lower than that of the control group (12.57 μmol / g, P<0.05). Since 1-MCP treatment can remove most of the oxygen free radicals in the fruit, it can delay membrane lipid peroxidation and effectively inhibit MDA accumulation. Furthermore, mustard oil contains a large amount of phenolic antioxidants, which can also prevent MDA accumulation in broccoli due to oxidative damage. Therefore, between 14 and 21 days, the increase in MDA content in the 1-MCP+MEO treatment group was the smallest, and it showed a significant difference from other treatment groups (1-MCP, MEO) (P<0.05), indicating that 1-MCP+MEO treatment can effectively delay the accumulation of MDA in broccoli.

[0050] Furthermore, total phenolic compounds are important antioxidants and a crucial indicator of fruit and vegetable quality. The decrease in total phenolic content in broccoli treated with 1-MCP+MEO was relatively small, consistently showing a significant difference compared to other treatment groups (P<0.05). Since 1-MCP can inhibit the respiratory metabolism of fruits and vegetables, and the active ingredients in mustard oil not only have antibacterial effects but also stimulate increased activity of total phenolic synthase in broccoli tissue, thus leading to an increase in phenolic compounds, the 1-MCP+MEO treatment not only exerts a synergistic antibacterial effect as a biological preservative but also enhances the inhibition of respiration, slows down browning, and delays the decrease in total phenolic content. Figure 6 As shown in a.

[0051] Furthermore, broccoli is rich in flavonoids, which can effectively scavenge hydroxyl free radicals. In this invention, the 1-MCP+MEO treatment not only exerts a synergistic effect as a biological preservative to inhibit bacteria, but also enhances the inhibition of respiration, slows down browning, and delays the decrease in total flavonoid content. Therefore, after 14 days, the total flavonoid content of the broccoli treated with 1-MCP+MEO was significantly higher than that of the control group (P<0.05), indicating that the broccoli preservation paper treatment can better maintain the total flavonoid content in broccoli. Figure 6 As shown in b.

[0052] Storage tests under the same conditions verified that the broccoli preservation paper prepared in Example 2 could achieve similar effects to the broccoli preservation paper prepared in Example 1, and will not be repeated here.

Claims

1. A broccoli preservation paper, comprising a paper-like carrier, characterized in that, It also includes a powdered Pickering emulsion freeze-dried on the aforementioned carrier, the components of which include 1-MCP, mustard oil, emulsifier and stabilizer, wherein the emulsifier is collagen and the stabilizer is chitosan and natural anthocyanins. Its preparation method includes the following steps: (1) Mix 1-MCP and mustard oil at a ratio of 0.5%-1.0% m / v, shake the mixture to dissolve it completely, and obtain a 1-MCP mustard oil solution; (2) Take the 1-MCP mustard oil solution and collagen obtained in step (1) and add them to deionized water at a ratio of 2%-5% v / v and 3%-6% m / v respectively to obtain a mixture. Under the condition of ice water bath, the mixture is ultrasonically emulsified to obtain an emulsion. (3) Glacial acetic acid and glycerol are added separately to fresh deionized water to obtain a deionized aqueous solution, wherein the concentrations of the glacial acetic acid and glycerol in the deionized aqueous solution are 0.2% v / v and 50% m / v, respectively. Chitosan nanoparticles and natural anthocyanins were added to the above deionized aqueous solution in proportions of 3%-5% m / v and 4%-6% m / v, respectively. Then, the mixture was homogenized at high speed. Finally, the emulsion obtained in step (2) was added to the deionized aqueous solution and stirred thoroughly at room temperature to obtain Pickering emulsion. (4) The Pickering emulsion from step (3) is pre-frozen at −20℃ for 12h, and then freeze-dried under vacuum for 24h~36h until all water is removed to obtain freeze-dried Pickering emulsion. After spray drying, the freeze-dried Pickering emulsion is in powder form. (5) Using electrostatic spraying, the powdered Pickering emulsion is freeze-dried and evenly sprayed onto the surface of the carrier. Another identical carrier is attached to the side of the carrier with powder. The two carriers are then bonded together around the edges using an adhesive to obtain broccoli preservation paper.

2. The broccoli preservation paper as described in claim 1, characterized in that, The carrier is absorbent paper.

3. An application of the broccoli preservation paper as described in claim 1 or 2, characterized in that, When using, lay the broccoli preservation paper flat on the surface of the broccoli, and then seal and store the broccoli and broccoli preservation paper together.

4. The application of the broccoli preservation paper as described in claim 3, characterized in that, The amount of broccoli preservation paper used is 10-15 kg / sheet, and the area of ​​each broccoli preservation paper is 30cm×40cm.

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