Disinfection method for preventing tomato pedicels from mildewing

Abstract

The invention discloses a disinfection method for preventing tomato pedicels from mildewing. Cage-shaped nano platinum liquid is adopted as an effective component and is matched with carbon dot powder and nano calcium carbonate to obtain the platinum nano disinfectant for preventing the tomato pedicels from mildewing. Compared with the prior art, the platinum nano disinfectant used in the disinfection method has efficient sterilization capacity on fungi / bacteria, all the components are green and environmentally friendly, the disinfection method can be used for sterilization and fresh keeping of tomato fruits, and the weight loss rate of tomatoes in the storage process can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of tomato fruit stem mildew prevention, and in particular to a disinfection method for preventing tomato fruit stem from mildew. Background Art

[0002] Tomato is a herbaceous plant of the Solanaceae family, an annual or perennial plant, native to South America. It has only been cultivated in my country for a few decades as a commercial vegetable. Due to its wide adaptability and rich nutritional value, it has developed rapidly and has become one of the agricultural pillar industries in several provinces such as Xinjiang. During transportation, tomatoes face the risk of mold on the fruit stem and infection by various bacteria on the fruit surface, causing the fruit stem to mold and rot when it arrives at the customer end, seriously affecting the quality of tomatoes after harvest; therefore, developing a tomato disinfection method suitable for production is the main technical means to reduce the activity of harmful microorganisms and reduce yield losses.

[0003] At present, the methods used to prevent and control fruit and vegetable diseases at home and abroad mainly include chemical, physical and biological methods, or a combination of several methods. Fruits and vegetables treated by these methods can prolong the freshness and quality of fruits and vegetables and inhibit the growth and reproduction of pathogens. However, tomato planting bases mainly use chemical pesticides to inhibit pathogens on the calyx of tomato fruit surface before harvest, which will increase pesticide residues. As people pay more attention to the negative effects of pesticides, however, the use of disinfectants to disinfect and sterilize picked tomatoes is prone to corroding tomato fruit pedicles. Therefore, it is very necessary to use an efficient, low-toxic, green, environmentally friendly and pollution-free disinfectant to replace chemical pesticides and fungicides in agricultural fruits and vegetables without corroding tomato fruit pedicles.

[0004] CN102047947A discloses a preservative for citrus anti-corrosion and disease prevention, which is prepared by shellac powder: ascorbic acid: sodium benzoate: citric acid: calcium stearate: calcium peroxide: starch: water = 0-20: 0.5-1.5: 1.0-5.0: .0-10: 0.1-1.0: 45-60: 12-26: 160-190. These raw materials are prepared according to the weight ratio to improve the effect of reducing rot and extending the shelf life of citrus after picking. However, the invention does not have data to show whether the effect in actual application can achieve the effect of antibacterial sterilization and extending the shelf life.

[0005] CN112352830A discloses a post-treatment method for citrus fruits, which increases the shelf life of citrus fruits by soaking them in carbendazim and then waxing them. However, the pesticide carbendazim and the waxing method used in the invention have high pesticide residues, which are unsafe for human body and do not conform to the concept of green environmental protection. Summary of the invention

[0006] In view of the above-mentioned defects of the prior art, the object of the present invention is to provide a disinfection method for preventing tomato stems from mold. The disinfectant used in the disinfection method has a high efficiency in killing fungi / bacteria and each component is green and environmentally friendly. It can be used for fruit sterilization and preservation, and can also reduce the weight loss rate of tomatoes during storage.

[0007] To achieve the above object, the present invention provides a disinfection method for preventing tomato stems from becoming moldy, comprising the following steps:

[0008] Spray the platinum nano disinfectant on the surface of picked tomatoes and on the fruit stems; the platinum nano disinfectant is prepared before use.

[0009] The platinum nano disinfectant is composed of the following components in percentage by mass: 0.1-1.0% caged nano platinum liquid, 0.1-1.0% saturated sodium bicarbonate solution, and the balance is water;

[0010] Further preferably, the preparation method of the platinum nano disinfectant is: uniformly mixing the liquid component and the solid component in a mass ratio of 10-50:1-5 to obtain the platinum nano disinfectant;

[0011] The liquid component is composed of the following components in percentage by mass: 0.1-1.0% of cage-shaped nano-platinum liquid, 0.1-1.0% of saturated sodium bicarbonate solution, and the balance is water.

[0012] As a further illustration of the present invention, the caged nano-platinum liquid of the present invention has a nano-platinum particle size of about 2-5 nm, a cage-like structure, and uniform particles that are not easy to aggregate and settle. The addition of saturated sodium bicarbonate solution can serve as a buffer; when the pH value in the system fluctuates due to the introduction of trace impurities or slight changes in other components, sodium bicarbonate can resist such changes, thereby keeping the pH value of the system relatively stable and improving the platinum nano-disinfectant.

[0013] Preferably, the disinfectant needs to be diluted 10-1500 times when used.

[0014] Further preferably, the spraying amount of the disinfectant is 300-800 mL per 100 kg of tomato fruit.

[0015] Preferably, the method for preparing the caged nano-platinum liquid comprises the following steps, measured in parts by mass:

[0016] Under nitrogen protection, 1-5 parts of chloroplatinate, 5-20 parts of polyvinyl pyrrolidone and 50-100 parts of anhydrous ethanol are mixed evenly, 0.1-0.5 parts of trehalose are added, and the mixture is reacted at 80-100° C. and 800-1200 rpm for 1-3 hours to obtain caged nano-platinum liquid.

[0017] As a further illustration of the present invention, the caged nano platinum particles in the caged nano platinum liquid have a good killing effect on microorganisms such as bacteria, fungi and viruses. When in contact with the cell membrane of the microorganism, the protective peptidoglycan layer can be destroyed, resulting in the rupture of the outer membrane of lipoproteins, stopping cell division and causing cell death; and the caged nano platinum particles can promote the increase of reactive oxygen levels to cause oxidative stress, damage components such as intracellular proteins, lipids and DNA, interact with DNA and interrupt the cell transport system, inhibit ATP-dependent protein synthesis and induce DNA damage to hinder microbial growth; the generation of reactive oxygen ROS can delay the electron transfer of the damaged plasma membrane along the respiratory chain, thereby playing a strong antibacterial role. However, the equipment used for the nano platinum particles synthesized by physical methods is expensive and not suitable for mass production, and most chemical reactions will choose to add protective agents, which will affect the reactivity of the nano platinum particles. The method provided by the present invention is adopted to prepare caged nano platinum liquid. The method is simple, and the nano platinum particles have a particle size of about 2-5 nm, present a cage-like structure, and are uniform and not easy to aggregate and settle. Moreover, the cage-like structure can also increase the specific surface area and reaction sites of the nano platinum. Trehalose can be used as a dispersant to increase the viscosity of the reaction liquid, so that the movement of platinum nano particles generated in the reaction process in the reaction solution is restricted, and the aggregation of the nano platinum is further effectively inhibited, thereby increasing the stability of the caged nano platinum liquid.

[0018] Preferably, the solid component is selected from at least one of coffee carbon dot powder, nano calcium carbonate, coffee carbon dot powder and nano calcium carbonate composite.

[0019] Preferably, the method for preparing the coffee carbon dot powder comprises the following steps, calculated by weight:

[0020] 1-5 parts of coffee beans and 10-50 parts of water are added into a reaction kettle, reacted at 180-220°C for 6-10 hours, filtered, and the filtrate is dialyzed in water for 18-30 hours with a molecular weight cutoff of 1000-10000Da; then freeze-dried to obtain coffee carbon dot powder.

[0021] As a further illustration of the present invention, carbon dots are a new type of carbon nanomaterial with a particle size of less than 10nm and a rich surface of functional groups such as amino, carboxyl, amide and hydroxyl groups. The present invention prepares coffee carbon dot powder by a hydrothermal method. The coffee carbon dot powder has good dispersibility and is easily adsorbed on the surface of microorganisms. Its surface functional groups can destroy the cell wall and cell membrane of microorganisms through electrostatic or hydrophobic interactions, causing the contents of the cells such as DNA and protein to leak, thereby affecting the normal function of the bacteria and causing the death of the bacteria; it can induce the production of ROS, which will destroy the membrane structure of the microorganism, causing irreversible damage such as DNA chain breakage and oxidative damage; it can enter the interior of the microorganism, and combine with the DNA or RNA in the bacteria through electrostatic and hydrophobic interactions to destroy its structure, causing its gene transmission errors, thereby inhibiting growth and achieving an antibacterial effect. Due to the hydrogen donor behavior of coffee carbon dots, sp 2 The antioxidant capacity of the hybrid carbon domain and the precursor material has an important influence on its antioxidant performance, and the surface of the coffee carbon dots contains abundant functional groups such as amino, carboxyl, and hydroxyl, which can provide hydrogen ions to scavenge free radicals. Therefore, the coffee carbon dot powder prepared by the present invention also has excellent antioxidant properties.

[0022] Preferably, the preparation method of nano calcium carbonate comprises the following steps, calculated by mass: adding 0.1-1 part of sodium polyaspartate to 1-10 parts of 1-5wt% calcium chloride aqueous solution, stirring at room temperature and 800-1200rpm for 20-40min to obtain a mixed solution A; then dropping 1-10 parts of 1-5wt% sodium carbonate aqueous solution at a speed of 10mL / min, and then stirring at 800-1200rpm for 10-14h; then centrifuging at 8000-10000rpm for 20-40min, washing the solid with water for 2-4 times, and then drying at 40-60℃ for 6-8h to obtain nano calcium carbonate.

[0023] As a further illustration of the present invention, when the double decomposition method is used to prepare nano calcium carbonate, sodium polyaspartate can couple with calcium ions or carbonate ions to form a complex, and the complex forms colloidal particles as the cross-linking time increases. Sodium polyaspartate affects the formation of unit cells during the crystallization process, induces the formation of calcium carbonate with different crystal forms and morphologies, and inhibits its transformation to other crystal forms, forming spherical calcium carbonate with a particle size of about 430 nm. The spherical calcium carbonate is formed by closely stacking finer particles, and there are gaps between the particles, which has good adsorption properties.

[0024] Preferably, the method for preparing the composite of coffee carbon dot powder and nano-calcium carbonate comprises the following steps, calculated by weight:

[0025] 1-10 parts of coffee carbon dot powder and 10-50 parts of water are mixed evenly, and then 20-40 parts of nano-calcium carbonate are added, ultrasonically shaken at 40-80 kHz for 20-60 minutes, and then reacted at 800-1000 rpm for 16-32 hours, filtered, the filter cake is washed with water 2-4 times, and then dried at 50-70°C for 6-8 hours to obtain a composite of coffee carbon dot powder and nano-calcium carbonate.

[0026] The present invention uses a compound of coffee carbon dot powder and nano calcium carbonate as a solid component, and the coffee carbon dot powder can be adsorbed in the nano calcium carbonate through electrostatic and chemical effects to form a sustained-release structure; and the liquid component and the solid component are mixed, and the nano calcium carbonate in the solid component can be adsorbed and complexed with the caged nano platinum liquid in the liquid component, which can improve the stability of the disinfectant, reduce agglomeration and precipitation caused by the influence of the external environment, and enhance the antibacterial effect.

[0027] Beneficial effects of the present invention:

[0028] 1. Compared with the prior art, the present invention utilizes the interaction between various substances through reasonable proportions and optimizes the preparation process to obtain a platinum nano disinfectant. The platinum nano disinfectant obtained by the present invention not only has the antibacterial effect of the disinfectant itself, but also has the advantages of synergistic action of multiple antibacterial mechanisms to improve the antibacterial breadth and prolong the antibacterial time. At the same time, the disinfectant is also green and environmentally friendly and has no corrosive effect on tomato fruit stalks. It can also extend the storage time of picked tomato fruits and reduce the weight loss rate of fruits during the storage period.

[0029] 2. Compared with the prior art, the present invention compounds a liquid component containing caged nano-platinum with a solid component containing coffee carbon dot powder and nano-calcium carbonate. Nano-calcium carbonate can be adsorbed and complexed with the caged nano-platinum liquid in the liquid component, thereby improving the stability of the disinfectant, reducing agglomeration and precipitation caused by the influence of the external environment, and increasing the antibacterial ability of the disinfectant.

[0030] 3. Compared with the prior art, the present invention compounds a liquid component containing caged nano-platinum with a solid component containing coffee carbon dot powder and nano-calcium carbonate. The sustained-release particles formed by the coffee carbon dot powder and nano-calcium carbonate can complex with the nano-platinum particles to form an antibacterial barrier, which can reduce the occurrence of disease spots during storage of tomatoes and reduce the rate of tomato tissue damage, thereby reducing weight loss. The coffee carbon dot powder also has antioxidant properties, which can regulate the physiological metabolic process of tomatoes and prevent the oxidative decomposition of flavor pigments and flavor substances. DETAILED DESCRIPTION

[0031] The parameters and sources of some raw materials in the embodiments of the present invention are as follows:

[0032] Coffee beans, variety: Typica, origin: Pu'er, Yunnan;

[0033] Polyvinylpyrrolidone, CAS: 9003-39-8, average molecular weight: 55000;

[0034] Fruit and vegetable fresh-keeping bags, specifications: length 2m*width 1.5m*height 1.5m, from Juxian Jinlei Plastic Products Co., Ltd.;

[0035] Sodium polyaspartate, CAS: 181828-06-8, product number: S28654, from Shanghai Yuanye Biotechnology Co., Ltd.;

[0036] Benzalkonium chloride, dosage form: liquid, total active ingredient content (calculated as benzalkonium chloride): 4% Fluoxathiocarb, dosage form: suspension, total active ingredient content: 43%;

[0037] Pyrimethanil, dosage form: suspension, total active ingredient content: 40%;

[0038] Iprodione, dosage form: wettable powder, total active ingredient content: 50%;

[0039] Fluoxetine, dosage form: suspension, total active ingredient content: 42.4%;

[0040] Iprodione, dosage form: suspension, total active ingredient content: 400g / L;

[0041] Thiophanate-methyl, formulation: wettable powder, total active ingredient content: 65% (52.5% thiophanate-methyl + 12.5% ​​ethophanate);

[0042] Fluopyram·pyrimidine, dosage form: suspension, total active ingredient content: 500g / L.

[0043] Example 1

[0044] A disinfection method for preventing tomato stems from becoming moldy comprises the following steps: diluting a platinum nano disinfectant by 20 times and spraying it on the surface of picked tomatoes and the stems.

[0045] The platinum nano disinfectant is composed of the following components in percentage by mass: 0.5% of caged nano platinum liquid, 0.5% of saturated sodium bicarbonate solution, and the balance is water.

[0046] The preparation method of the cage-shaped nano-platinum liquid comprises the following steps:

[0047] Under nitrogen protection, 300 g of chloroplatinate, 1500 g of polyvinyl pyrrolidone and 8000 g of anhydrous ethanol were mixed evenly, 30 g of trehalose was added, and the mixture was reacted at 90° C. and 1000 rpm for 2 h to obtain a caged nano-platinum liquid.

[0048] Example 2

[0049] A disinfection method for preventing tomato stems from mold, which differs from Example 1 in that a platinum nano disinfectant is diluted 30 times and sprayed on the surface of picked tomatoes and the stems.

[0050] Example 3

[0051] A disinfection method for preventing tomato stems from mold, which differs from Example 1 in that a platinum nano disinfectant is diluted 40 times and sprayed on the surface of picked tomatoes and the stems.

[0052] Example 4

[0053] A disinfection method for preventing tomato stems from mold, which differs from Example 1 in that a platinum nano disinfectant is diluted 50 times and sprayed on the surface of picked tomatoes and the stems.

[0054] Example 5

[0055] A disinfection method for preventing tomato stems from becoming moldy comprises the following steps: diluting a platinum nano disinfectant by 20 times and spraying it on the surface of picked tomatoes and the stems.

[0056] The preparation method of the platinum nano disinfectant is: the liquid component and the solid component are uniformly mixed in a mass ratio of 25:2 to obtain a ready-to-use platinum nano disinfectant;

[0057] The liquid component is composed of the following components in percentage by mass: 0.5% of cage-shaped nano-platinum liquid, 0.5% of saturated sodium bicarbonate solution, and the balance is water.

[0058] The preparation method of the caged nano-platinum comprises the following steps:

[0059] Under nitrogen protection, 300 g of chloroplatinate, 1500 g of polyvinyl pyrrolidone and 8000 g of anhydrous ethanol were mixed evenly, 30 g of trehalose was added, and the mixture was reacted at 90° C. and 1000 rpm for 2 h to obtain a caged nano-platinum liquid.

[0060] The preparation method of the solid component comprises the following steps:

[0061] 500 g of coffee carbon dot powder and 2500 g of water were mixed evenly, and then 3000 g of nano-calcium carbonate was added and ultrasonically vibrated at 60 kHz for 40 min, and then reacted at 900 rpm for 24 h. The filter cake was washed with water three times and then dried at 60°C for 7 h to obtain a composite of coffee carbon dot powder and nano-calcium carbonate, i.e., a solid component.

[0062] The method for preparing the coffee carbon dot powder comprises the following steps:

[0063] 300 g of coffee beans and 3000 g of water were added into a reactor, reacted at 200° C. for 8 h, filtered, and the filtrate was dialyzed in water for 24 h with a molecular weight cutoff of 5000 Da; then freeze-dried to obtain coffee carbon dot powder.

[0064] The preparation method of the nano calcium carbonate comprises the following steps:

[0065] Add 50 g of sodium polyaspartate to 500 g of 3 wt % calcium chloride aqueous solution, stir at room temperature and 1000 rpm for 30 min; then add 500 g of 3 wt % sodium carbonate aqueous solution dropwise at a speed of 10 mL / min, and then stir at 1000 rpm for 12 h; then centrifuge at 9000 rpm for 30 min, wash the solid with water 3 times, and then dry at 50° C. for 7 h to obtain nano calcium carbonate.

[0066] Example 6

[0067] A disinfection method for preventing tomato stems from mold, which differs from Example 5 in that the preparation method of the platinum nano disinfectant comprises the following steps:

[0068] The preparation method of the platinum nano disinfectant is: the liquid component and the solid component are uniformly mixed in a mass ratio of 25:2 to obtain a ready-to-use platinum nano disinfectant;

[0069] The liquid component is composed of the following components in percentage by mass: 0.5% of cage-shaped nano-platinum liquid, 0.5% of saturated sodium bicarbonate solution, and the balance is water.

[0070] The preparation method of the cage-shaped nano-platinum liquid is consistent with that of Example 5.

[0071] The solid component is nano calcium carbonate, and its preparation method is consistent with that in Example 5.

[0072] Example 7

[0073] A disinfection method for preventing tomato stems from mold, which differs from Example 5 in that the preparation method of the platinum nano disinfectant comprises the following steps:

[0074] The preparation method of the platinum nano disinfectant is: the liquid component and the solid component are uniformly mixed in a mass ratio of 25:2 to obtain a ready-to-use platinum nano disinfectant;

[0075] The liquid component is composed of the following components in percentage by mass: 0.5% of cage-shaped nano-platinum liquid, 0.5% of saturated sodium bicarbonate solution, and the balance is water.

[0076] The preparation method of the cage-shaped nano-platinum liquid is consistent with that of Example 5.

[0077] The solid component is coffee carbon dot powder, and its preparation method is consistent with Example 5.

[0078] Comparative Example 1

[0079] A disinfection method for preventing tomato stems from mold. The disinfectant comprises the following steps: evenly mixing 500g of coffee carbon dot powder and 2500g of water, then adding 3000g of nano-calcium carbonate, ultrasonically oscillating at 60kHZ for 40min, then reacting at 900rpm for 24h, filtering, washing the filter cake with water for 3 times, and then drying at 60°C for 7h to obtain a compound of coffee carbon dot powder and nano-calcium carbonate, which is then diluted 20 times and sprayed on the surface of picked tomatoes and stems.

[0080] The preparation method of the coffee carbon dot powder is consistent with that in Example 5.

[0081] The preparation method of the nano calcium carbonate is consistent with that of Example 5.

[0082] Comparative Example 2

[0083] A disinfection method for preventing tomato stems from becoming moldy is disclosed, which differs from Example 1 in that peracetic acid is diluted 200 times and sprayed on the surface of picked tomatoes and the stems.

[0084] Comparative Example 3

[0085] A disinfection method for preventing tomato stems from becoming moldy is disclosed, which differs from Example 1 in that benzalkonium chloride is diluted 300 times and sprayed on the surface of picked tomatoes and the stems.

[0086] Comparative Example 4

[0087] A disinfection method for preventing tomato stems from mold, which differs from Example 1 in that fluopicolide is diluted 1000 times and sprayed on the surface of picked tomatoes and the stems.

[0088] Comparative Example 5

[0089] A disinfection method for preventing tomato stems from mold, which differs from Example 1 in that pyrimethanil is diluted 600 times and sprayed on the surface of picked tomatoes and the stems.

[0090] Comparative Example 6

[0091] A disinfection method for preventing tomato stems from becoming moldy is disclosed, which differs from Example 1 in that cyprodinil is diluted 800 times and sprayed on the surface of picked tomatoes and the stems.

[0092] Comparative Example 7

[0093] A disinfection method for preventing tomato stems from mold, which differs from Example 1 in that fluazifop-sodium is diluted 1000 times and sprayed on the surface of picked tomatoes and the stems.

[0094] Comparative Example 8

[0095] A disinfection method for preventing tomato stems from mold, which differs from Example 1 in that isoflurane is diluted 1000 times and sprayed on the surface of picked tomatoes and the stems.

[0096] Comparative Example 9

[0097] A disinfection method for preventing tomato stems from becoming moldy is disclosed, which differs from Example 1 in that ethofluthrin is diluted 1500 times and sprayed on the surface of picked tomatoes and the stems.

[0098] Comparative Example 10

[0099] A disinfection method for preventing tomato stems from mold, which differs from Example 1 in that fluopyram·pyrimethanil is diluted 1000 times and sprayed on the surface of picked tomatoes and the stems.

[0100] Comparative Example 11

[0101] A tomato preservation method comprises putting picked tomato fruits into a fruit and vegetable preservation bag.

[0102] Test Example 1

[0103] Antibacterial performance test

[0104] Test method: Select moldy tomatoes in the greenhouse, soak them in saline, and then ultrasonically vibrate them at 60 kHz for 5 minutes. Take 10 mL of the saline after ultrasonic vibration and put it into PDA liquid culture medium. Incubate it at 37 ° C for 24 hours, and determine the number of bacteria by measuring the absorbance (OD) value. Then, use sterile water to make a 1×10 6 CFU / mL of bacterial suspension; 100 μL of the prepared bacterial suspension was aspirated, added to a liquid culture medium in which PDA and the disinfectants configured in Examples 1-7 and Comparative Examples 1-10 were mixed in a mass ratio of 10:1, placed in an incubator at 25°C for dark culture for 3 days, and then the colony count (CFU / g) was calculated by the experimental method of the plate colony counting method. The test results are shown in Table 1.

[0105] Table 1 Antibacterial performance test

[0106]

[0107]

[0108] By comparing Examples 1-7 and Comparative Examples 1-10, it can be found that the number of colonies in Examples 1-7 and Comparative Examples 1-3 is small. The reason may be that the disinfectant prepared in Examples 1-7 contains nano-platinum particles with strong disinfection ability; Comparative Example 2 is peracetic acid, which has strong oxidizing properties and can oxidize the chemical substances in the bacterial cells, causing redox reactions, thereby destroying the cell structure and function; the benzalkonium chloride in Comparative Example 3 is a quaternary ammonium salt disinfectant, which is a cationic surfactant and can be highly aggregated on the bacterial surface, affecting the permeability of the bacterial cell membrane and causing the bacterial cytoplasm to extravasate, thereby hindering the cell metabolism of microorganisms and playing a killing role; the solid component coffee carbon dot powder and nano-calcium carbonate compound in Comparative Example 1, the coffee carbon dot powder can be adsorbed in the nano-calcium carbonate through electrostatic and chemical effects to form a sustained-release structure, and the carbon dots have good antibacterial properties.

[0109] Test Example 2

[0110] Inhibition zone test

[0111] Test method: Select moldy tomatoes in the greenhouse, soak them in saline, and then ultrasonically vibrate them at 60 kHz for 5 minutes. Take 10 mL of the saline after ultrasonic vibration and put it into PDA liquid culture medium. Incubate it at 37 ° C for 24 hours, and determine the number of bacteria by measuring the absorbance (OD) value. Then, use sterile water to make a 1×10 6 CFU / mL bacterial suspension; 100 μL of the prepared bacterial suspension was aspirated and added to the PDA solid culture medium, and the bacterial solution was evenly spread with a coating rod; a blank filter paper with a diameter of 6 mm was soaked in the disinfectants of Example 1, Examples 5-7, Comparative Examples 1-2 and Comparative Example 7, respectively, and then the filter paper was attached to the surface of the culture medium coated with bacteria, and then the plate was inverted in a 37°C biochemical incubator for 72 h, and the diameter (mm) of the inhibition zone was measured by the cross method. Five repeated experiments were set for each experimental group. The test results are shown in Table 2.

[0112] Table 2 Diameter of inhibition zone

[0113]

[0114] By comparing Example 1, Example 5-7, Comparative Example 1-2 and Comparative Example 7, it can be found that the diameter of the antibacterial circle of Example 1, Example 5-7 and Comparative Example 1 is higher than that of Comparative Example 2 and Comparative Example 7; Example 1, Example 5-7 and Comparative Example 1 can find that the diameter of the antibacterial circle of Example 5 is the highest, and the diameter of the antibacterial circle reaches 19.21 mm, indicating that it has excellent antibacterial effect. The reason for the analysis may be that the main component of Example 1 is Kaibei nano disinfectant, and the disinfection effect is mainly achieved through the action of nano-platinum particles to achieve antibacterial effect. Nano-platinum particles can promote the increase of active oxygen levels to cause oxidative stress, damage intracellular proteins, lipids and DNA components, interact with DNA and interrupt the cell transport system, inhibit ATP-dependent protein synthesis and induce DNA damage to hinder microbial growth; the generation of active oxygen ROS can delay the electron transfer of damaged plasma membrane along the respiratory chain, thereby playing a strong antibacterial effect.

[0115] The platinum nano disinfectant of Example 5 contains nano-platinum particles, coffee carbon dots, and nano-calcium carbonate, wherein the nano-calcium carbonate can first be adsorbed and loaded with the coffee carbon dot powder through electrostatic adsorption and chemical action to form a sustained-release structure, and when the solid component and the liquid component are mixed, the nano-platinum particles can be complexed with sodium polyaspartate to improve the stability of the disinfectant; from the perspective of the mechanism of action, the coffee carbon dots are easily adsorbed on the surface of the bacteria, and their surface functional groups can destroy the cell walls and cell membranes of microorganisms through electrostatic or hydrophobic interactions, causing the contents of the cells such as DNA and proteins to leak, thereby affecting the normal function of the bacteria and causing the death of the bacteria; it can induce the production of ROS, which will destroy the membrane structure of the microorganism, causing irreversible damage such as DNA chain breaks and oxidative damage; it can enter the interior of the microorganism, combine with the DNA or RNA in the bacteria through electrostatic and hydrophobic interactions to destroy its structure, causing its gene transmission errors, thereby inhibiting the growth of bacteria; it can increase the antibacterial action mode and produce synergistic effects with nano-platinum particles to improve the antibacterial effect.

[0116] Test Example 3

[0117] Corrosion rate test

[0118] The picked tomato fruits were checked for sterile spots and damage on the fruit stems, and then 500 mL was sprayed on the fruits and fruit stems according to the mass ratio for every 100 kg, and then the disinfectants prepared in Example 1, Examples 5-7, Comparative Examples 1-2 and Comparative Example 7 were sprayed, with 100 in each group, and five groups were set up in parallel. After the fruit surface was free of water, the samples were sent to a 10°C cold storage for storage, and a blank control group was added without spraying disinfectant. When the fruit stems were damaged, they were identified as being corroded by the disinfectant. The corrosion rate was statistically analyzed after 24 hours, and the corrosion rate calculation formula was as follows:

[0119] Corrosion rate (%) = (S1 / S0) × 100%

[0120] Where S1 is the tomato with fruit pedicle loss, and S0 is the number of experimental tomatoes;

[0121] The specific test results are shown in Table 3.

[0122] Table 3 Corrosion rate

[0123]

[0124] As can be seen from Table 2, by comparing Example 1, Examples 5-7, Comparative Examples 1-2 and Comparative Example 7, it can be found that the corrosion rates of tomato stalks in Comparative Example 7, Examples 5-7 and Comparative Example 1 are relatively low. By comparing Comparative Example 7, Examples 5-7 and Comparative Example 1, it can be found that the corrosion rate of tomato stalks in Example 5 is the lowest, only 0.02%. Analysis shows that the reason may be that in the Kaibei disinfectant of Example 1, it is in direct contact with the surface of tomatoes, and the high content of nano-platinum particles has a strong catalytic effect, which can easily destroy the pectin structure and cell membrane structure, and may cause damage to the tomato stalk; in the platinum nano disinfectant of Example 5, the slow-release particles formed by nano-calcium carbonate and coffee carbon dot powder can adhere to the surface of the fruit stalk to produce a protective effect. The slow-release particles also have a similar buffer effect, which can adjust the microenvironment and reduce the corrosion rate; the liquid part of the platinum nano disinfectant of Comparative Example 1 does not contain caged nano-platinum, and its direct contact corrosion rate with the fruit stalk cells is lower than that of Example 1; the solid part of the platinum nano disinfectant of Example 6 does not contain coffee carbon dot powder, which may be because nano-calcium carbonate has an adsorption effect and can adhere to the surface of tomatoes to produce a protective effect, and its direct contact corrosion rate with the fruit stalk cells is lower than that of Example 7; the solid part of the platinum nano disinfectant of Example 7 does not contain nano-calcium carbonate, which may be because coffee carbon dot powder has a certain antioxidant effect, which can reduce the corrosion of some compounds on the fruit stalk cells and thus reduce the corrosion rate.

[0125] The peracetic acid in Comparative Example 2 is a strong oxidant, and the peroxide bond in contact with the tomato fruit stalk is easily broken and the active oxygen atoms are released, resulting in the destruction of the cell structure; the flutolanil in Comparative Example 7 belongs to the methoxyacrylate fungicide, which is a pesticide and mainly acts on fungi. This may be because the tomato fruit stalk has a relatively rough structure and is easy to absorb disinfectants, resulting in increased concentration and a small amount of corrosion, but it may cause accumulation of pesticides in the tomato fruit.

[0126] Test Example 4

[0127] Tomato weight loss test

[0128] 100 tomatoes of similar size and intact surface that were 80 to 90% ripe and just picked were selected from each group, and were treated by the methods of Example 1, Example 5-7, Comparative Example 1-2, Comparative Example 7, and Comparative Example 11, respectively, and recorded as Example 1, Example 5-7, Comparative Example 1-2, Comparative Example 7, and Comparative Example 11 groups; another group of tomatoes was not treated and served as a blank control group; then each group was placed in a constant temperature box at 25° C. and 45% relative humidity for 3 days, 5 days, 10 days, and 15 days, respectively, and the changes in the weight of each group of tomatoes at different statistical days were observed, and the weight loss rate of the tomatoes with the extension of the storage time was calculated. The weight loss rate calculation formula is as follows:

[0129] Weight loss rate (%) = (M0-M1) ÷ M0 × 100%;

[0130] Where M1 is the mass of tomatoes at different statistical days, and M0 is the mass of tomatoes just picked;

[0131] The specific test results are shown in Table 4.

[0132] Table 4 Weight loss rate of tomatoes

[0133]

[0134]

[0135] By comparing Example 1, Example 5-7, Comparative Example 1-2, Comparative Example 7, Comparative Example 11 and the blank group, it can be found that the weight loss rate of Example 5-7 and Comparative Example 1 is lower; by comparing Example 5-7 and Comparative Example 1, it can be found that the weight loss rate of Example 5 is the lowest, and the weight loss rate of storage for 15 days is only 13.81%. The reason for this may be that Example 1, Example 5-7, and Comparative Example 1 have antibacterial effects that can reduce the occurrence of disease spots during tomato storage and reduce the rate of tomato tissue damage, thereby reducing weight loss; the peracetic acid in Comparative Example 2 can reduce the occurrence of disease spots during tomato storage and reduce the rate of tomato tissue damage, but peracetic acid is easy to decompose and has, so the weight loss rate will be higher; the thiazolinamide in Comparative Example 7 belongs to the methoxyacrylate fungicide, and its mechanism of action is to deplete cell energy by inhibiting the cytochrome bc1 complex in the respiratory electron transport chain of pathogens, leading to cell death, but thiazolinamide belongs to the pesticide class, and direct use on fruits and vegetables may cause safety hazards; the polyethylene film in Comparative Example 11 has barrier properties and can effectively prevent water The carbon dioxide content in tomatoes will not be lost to the outside world, and the respiration of tomatoes themselves will increase the carbon dioxide content, which can reduce the consumption of organic matter and thus reduce the weight loss rate; the sustained-release particles formed by the coffee carbon dot powder and nano-calcium carbonate in the solid components of the platinum nano-disinfectant of Example 5 may form a physical protective film on the surface of tomatoes, which can reduce the direct contact between tomatoes and the external environment and reduce the evaporation rate of water; the sustained-release particles formed by the coffee carbon dot powder and nano-calcium carbonate can be chelated with nano-platinum particles to form an antibacterial barrier, which can reduce the occurrence of disease spots during the storage of tomatoes and reduce the rate of tomato tissue destruction, thereby reducing weight loss; the coffee carbon dot powder also has antioxidant properties, which can regulate the physiological metabolism of tomatoes and prevent the oxidative decomposition of flavor pigments and flavor substances.

Claims

1. A disinfection method for preventing tomato stems from becoming moldy, characterized in that: Spray platinum nano disinfectant on the surface and stems of picked tomatoes; The platinum nano disinfectant is composed of the following components in percentage by mass: 0.1-1.0% caged nano platinum liquid, 0.1-1.0% saturated sodium bicarbonate solution, and the balance is water; Alternatively, the preparation method of the platinum nano disinfectant is: the liquid component and the solid component are evenly mixed in a mass ratio of 10-50:1-5 to obtain the platinum nano disinfectant; the liquid component is composed of the following components in mass percentage: 0.1-1.0% caged nano platinum liquid, 0.1-1.0% saturated sodium bicarbonate solution, and the balance is water.

2. The disinfection method for preventing tomato stems from becoming moldy as claimed in claim 1, characterized in that: The disinfectant needs to be diluted to 10-1500 times when used.

3. The disinfection method for preventing tomato stems from becoming moldy as claimed in claim 1, characterized in that: The spraying amount of the disinfectant is 300-800 mL per 100 kg of tomato fruit.

4. The disinfection method for preventing tomato stems from becoming moldy according to claim 1, characterized in that: The preparation method of the caged nano-platinum liquid comprises the following steps, calculated by mass: under nitrogen protection, 1-5 parts of chloroplatinate, 5-20 parts of polyvinyl pyrrolidone and 50-100 parts of anhydrous ethanol are uniformly mixed, 0.1-0.5 parts of trehalose are added, and the mixture is reacted at 80-100° C. and 800-1200 rpm for 1-3 hours to obtain the caged nano-platinum liquid.

5. The disinfection method for preventing tomato stems from mold as claimed in claim 1, characterized in that: The solid component is selected from at least one of coffee carbon dot powder, nano calcium carbonate, coffee carbon dot powder and nano calcium carbonate compound.

6. The disinfection method for preventing tomato stems from becoming moldy as claimed in claim 5, characterized in that: The method for preparing the coffee carbon dot powder comprises the following steps, calculated by weight: 1-5 parts of coffee beans and 10-50 parts of water are added into a reaction kettle, reacted at 180-220°C for 6-10 hours, filtered, and the filtrate is dialyzed in water for 18-30 hours with a molecular weight cutoff of 1000-10000Da; then freeze-dried to obtain coffee carbon dot powder.

7. The disinfection method for preventing tomato stems from becoming moldy as claimed in claim 5, characterized in that: The preparation method of nano calcium carbonate comprises the following steps, measured by weight: 0.1-1 part of sodium polyaspartate is added to 1-10 parts of 1-5wt% calcium chloride aqueous solution, and the mixture is stirred at room temperature and 800-1200rpm for 20-40min to obtain a mixed solution A; then 1-10 parts of 1-5wt% sodium carbonate aqueous solution are added dropwise at a speed of 10mL / min, and then stirred at 800-1200rpm for 10-14h; then centrifuged at 8000-10000rpm for 20-40min, the solid is washed with water for 2-4 times, and then dried at 40-60℃ for 6-8h to obtain nano calcium carbonate.

8. The disinfection method for preventing tomato stems from becoming moldy as claimed in claim 5, characterized in that: The preparation method of the coffee carbon dot powder and nano calcium carbonate composite comprises the following steps, calculated by weight: 1-10 parts of coffee carbon dot powder and 10-50 parts of water are mixed evenly, and then 20-40 parts of nano-calcium carbonate are added, ultrasonically shaken at 40-80 kHz for 20-60 minutes, and then reacted at 800-1000 rpm for 16-32 hours, filtered, the filter cake is washed with water 2-4 times, and then dried at 50-70°C for 6-8 hours to obtain a composite of coffee carbon dot powder and nano-calcium carbonate.

Images