Ripening coating for vegetables and fruits as well as preparation method and application of ripening coating

Abstract

The invention belongs to the field of vegetable and fruit preservation and transportation, and particularly relates to a ripening coating for vegetables and fruits and a preparation method and application of the ripening coating. The ripening coating for vegetables and fruits comprises a connecting layer, a functional layer and a film forming layer which are sequentially compounded, the connecting layer is used for connecting the carrier and the functional layer; the functional layer is prepared from the following raw materials in parts by weight: 25 to 41 parts of vinyl acetate, 0.5 to 2.5 parts of propylene glycol methyl ether acetate, 3 to 10 parts of plasticizer, 6 to 20 parts of ethephon and 1 to 16 parts of epoxy resin; and the film forming layer is used for protecting the functional layer. By coating the inner surface of the carton, the strength and original functions of the corrugated carton are not affected while the carton is endowed with a ripening function, and the treatment process is relatively simple and easy to implement.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of vegetable and fruit preservation and transportation, and particularly relates to a vegetable and fruit ripening coating and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of global trade integration and e-commerce, the cross-regional circulation of vegetables and fruits is becoming increasingly frequent. For post-ripening vegetables and fruits such as mangoes, kiwis, bananas, etc., the ripening process is irreversible, and if picked after complete ripening, they are prone to rot and deterioration during transportation and storage, resulting in loss of commodity value. Therefore, the industry generally adopts the mode of "unripe picking and post-transportation ripening", that is, picking vegetables and fruits that are 70-80% ripe, placing them in a semi-dormant state by controlling the storage environment, and then performing ripening treatment after reaching the sales terminal or the hands of consumers.

[0003] However, the existing ripening methods have many defects: first, the commonly used ethylene ripening agent needs to be prepared separately and placed in a container before being placed with the vegetables and fruits in a sealed space, which is cumbersome to operate, and the dosage of the ripening agent is difficult to accurately control, which can easily lead to over-ripening or insufficient ripening; second, the ripening agent directly contacts the vegetables and fruits, and if not thoroughly cleaned, the residual components can pose potential risks to human health; third, the ripening needs of different vegetables and fruits differ greatly, and the existing ripening methods cannot achieve simultaneous adaptive ripening of multiple vegetables and fruits; fourth, the traditional ripening process lacks controllability, and the ripening start time and ripening rate cannot be flexibly adjusted according to the transportation period and sales demand, resulting in some vegetables and fruits not being ripe when reaching the hands of consumers, which requires additional waiting, seriously affecting the consumer experience.

[0004] In addition, the existing corrugated cartons, as the main packaging carriers for vegetables and fruits, only have bearing and protection functions and do not have additional functions such as ripening, and the functions are single. If the ripening function can be integrated on the packaging carrier to realize "transportation-ripening" integration, the above technical problems will be effectively solved. Therefore, it is of important practical application value to develop a vegetable and fruit ripening coating with simple process, controllable ripening, safety and environmental protection, and apply it to transportation packaging. SUMMARY

[0005] In view of the problems of existing vegetable and fruit ripening methods such as cumbersome operation, poor controllability, insufficient safety, and single function of packaging carriers, the present application provides a vegetable and fruit ripening coating and a preparation method and application thereof. The coating can be integrated into packaging carriers such as corrugated cartons to realize controllable ripening during vegetable and fruit transportation, improve consumer experience, and at the same time ensure the original performance of the packaging carrier.

[0006] The technical solution of the present application is as follows:

[0007] The application provides a fruit and vegetable ripening coating, which comprises a connecting layer, a functional layer and a film-forming layer arranged in sequence.

[0008] The connecting layer is used for connecting the carrier and the functional layer.

[0009] The functional layer is composed of the following raw materials in parts by weight: 25-41 parts by weight of vinyl acetate, 0.5-2.5 parts by weight of propylene glycol methyl ether acetate, 3-10 parts by weight of a plasticizer, 6-20 parts by weight of ethephon and 1-16 parts by weight of an epoxy resin.

[0010] The film-forming layer is used for protecting the functional layer.

[0011] Vinyl acetate is used as a base material, has good film-forming property and adhesion, and provides a stable bearing matrix for the functional components; propylene glycol methyl ether acetate is used as a solvent, can improve the compatibility of the raw materials, and promotes the uniformity of mixing; the plasticizer is selected from one or more of dibutyl phthalate, dioctyl phthalate, tributyl citrate and epoxy soybean oil, and can improve the flexibility and ductility of the functional layer, and avoid cracking of the coating; ethephon is used as a ripening active component, can slowly release ethylene gas after being contacted with water, ethylene can enhance the activity of enzymes in fruits and vegetables, accelerate respiration and organic matter conversion, and promote fruit ripening; the epoxy resin is a thermosetting resin, can form a dense network structure, prevents ethephon from being volatilized in advance during transportation and storage, and ensures the stability of the ripening effect.

[0012] The film-forming layer is used for sealing and protecting the functional layer, avoids the functional layer from reacting in advance; the film-forming layer can block the contact of external moisture with the functional layer, avoids the ripening reaction from starting in advance; meanwhile, the air permeable hole can ensure the smooth release of ethylene gas, and the ethylene gas contacts fruits and vegetables to play a ripening role.

[0013] As a specific embodiment of the application, the carrier is a paperboard, and the paperboard is preferably a paperboard for a corrugated carton. The coating is coated on the inner surface of the carton, does not affect the bearing strength and protection performance of the carton.

[0014] As a specific embodiment of the application, the functional layer further comprises 2-8 parts by weight of a natural plant extract; preferably, the natural plant extract is one or more of banana peel extract, mango leaf extract and tomato stem extract.

[0015] ​As a specific embodiment of the present application, the preparation method of the natural plant extract is as follows: taking fresh plant raw materials (banana peel, mango leaves or tomato stems), washing and crushing to a particle size of 1-3 mm, adding deionized water at a solid-liquid ratio of 1:(8-15), constant temperature extraction at 50-70℃ for 2-4h, then high speed centrifugation at 8000-12000r / min for 15-25min, taking the supernatant and filtering through a 0.22-0.45μm microporous filter, vacuum concentration of the filtrate at 40-50℃ to a solid content of 25-40wt%, and obtaining the natural plant extract.

[0016] As a specific embodiment of the present application, the connecting layer is a water-based environmentally friendly adhesive. Such adhesive is environmentally friendly and non-toxic, and has good compatibility with paperboard and functional layer, and high bonding strength.

[0017] As a specific embodiment of the present application, the water-based environmentally friendly adhesive includes polyvinyl acetate adhesive, water-based polyurethane adhesive, and starch-based composite adhesive.

[0018] As a specific embodiment of the present application, the water-based environmentally friendly adhesive has a solid content of 30-50wt% and a viscosity of (25℃).

[0019] As a specific embodiment of the present application, the film-forming layer is a polyvinyl chloride film, a polyethylene film, a polypropylene film or a polylactic acid film, with a film thickness of 10-50μm, and the surface of the film-forming layer is provided with air permeable holes with a hole diameter of 1-5μm and a hole density of 10-50 / cm 2 .

[0020] As a specific embodiment of the present application, the plasticizer is one or more of dibutyl phthalate, dioctyl phthalate, tributyl citrate and epoxy soybean oil.

[0021] In a second aspect, the present application provides a preparation method of the above-mentioned fruit and vegetable ripening coating, which adopts dry mixing.

[0022] As a specific embodiment of the present application, the method comprises the following steps:

[0023] (1) Functional layer preparation: weighing the vinyl acetate, propylene glycol methyl ether acetate, plasticizer, ethephon and epoxy resin according to the weight ratio, mixing at a temperature of 50-70℃ and a rotation speed of 800-1200r / min for 15-30min to obtain a functional layer slurry;

[0024] (2) Connecting layer coating: uniformly coating the connecting layer material on the surface of the carrier by roller coating process, with a coating amount of 10-30g / m 2 , and then drying at 60-80℃ for 5-10min to form the connecting layer;

[0025] (3) Functional layer composite: the functional layer slurry prepared in step (1) is coated on the surface of the connecting layer by means of a doctor blade coating method, the coating thickness is 50-150 μm, and the coating is cured at 70-90 °C for 20-40 min;

[0026] (4) Film-forming layer composite: the film-forming layer is coated on the surface of the cured functional layer by means of a hot-pressing composite process, the hot-pressing temperature is 100-140 °C, the pressure is 0.3-0.8 MPa, and the composite time is 5-15 s, thereby obtaining the ripening coating for vegetables and fruits.

[0027] The connecting layer material (water-based environmentally friendly glue) is uniformly coated on the surface of the paperboard carrier by means of a roller coating process (roller coating can realize uniform coating, and the coating amount is easy to control), and the coating amount is 10-30 g / m 2 (the coating amount is too low, the bonding strength is insufficient, and too high coating amount is easy to cause the glue to penetrate the paperboard, thereby affecting the strength; 10-30 g / m 2 , the bonding strength and the performance of the paperboard can be balanced), and then the coated paperboard is dried at 60-80 °C for 5-10 min (low-temperature drying can avoid deformation of the paperboard, and the glue moisture can be removed, thereby ensuring the bonding strength), thereby forming the connecting layer.

[0028] The film-forming layer is coated on the surface of the cured functional layer by means of a hot-pressing composite process, the hot-pressing temperature is 100-140 °C (the temperature range can soften the film-forming layer and tightly adhere to the functional layer, and the activity of the functional components is not damaged), the pressure is 0.3-0.8 MPa (the pressure is too low, the adhesion is not tight, and too high pressure is easy to cause the air permeable holes to be blocked; the pressure of 0.3-0.8 MPa can ensure the composite effect), and the composite time is 5-15 s, thereby obtaining the ripening coating for vegetables and fruits.

[0029] As a specific embodiment of the present application, the natural plant extract is further added in step (1).

[0030] As a specific embodiment of the present application, the natural plant extract is added as follows: the vinyl acetate, propylene glycol methyl ether acetate, plasticizer and epoxy resin are mixed for 10 min, and then the ethephon and the natural plant extract are added and mixed for 5-20 min, thereby ensuring that the natural plant extract and the ethephon are uniformly dispersed, and avoiding that the local concentration is too high.

[0031] As a specific embodiment of the present application, the mixing process in step (1) adopts a segmented stirring method: first stirring at a speed of 800-900 r / min for 10-20 min, and then stirring at a speed of 1100-1200 r / min for 10-20 min. The segmented stirring can avoid that the natural plant extract is damaged in activity due to early high-speed shearing, and the precise feeding time can ensure that the ethephon and the natural plant extract are uniformly dispersed, and avoid that the local concentration is too high, thereby causing uneven ripening.

[0032] As a specific embodiment of the present application, the curing process in step (3) is divided into two stages: first pre-curing at 70-75℃ for 10-15min, and then final curing at 85-90℃ for 10-25min.

[0033] Segmented curing: first pre-curing at 70-75℃ for 10-15min (to preliminarily shape the functional layer and avoid component migration during subsequent final curing), and then final curing at 85-90℃ for 10-25min (to fully crosslink the epoxy resin and form a dense structure to fix the functional components).

[0034] In a third aspect, the present application provides the use of the fruit ripening coating or the fruit ripening coating prepared by the above preparation method in fruit transportation.

[0035] As a specific embodiment of the present application, the ripening cycle is regulated to 0.3-4.5d by adjusting the weight content of ethephon (6-20 parts) and the weight content of natural plant extract (2-8 parts) in the functional layer. There is a significant synergistic effect between the natural plant extract and ethephon: when the weight content of natural plant extract increases by 1 part, the weight of ethephon can be reduced by 0.8-1.2 parts, and the ripening cycle is shortened by 8%-12%.

[0036] For example: when only 10 parts of ethephon is used, the mango ripening cycle is 3.2d; when 3 parts of natural plant extract and 7 parts of ethephon are added, the mango ripening cycle is shortened to 2.1d, and the ripening efficiency is increased by 34.4%. This synergistic effect can reduce the amount of chemical ripening agent, reduce the safety risk, and improve the ripening efficiency, which is suitable for the differentiated needs of different fruits (such as kiwi fruit which needs 3-4d ripening, and banana which needs 1.5-2d ripening).

[0037] As a specific embodiment of the present application, the ripening rate is regulated by adjusting the humidity of the transportation environment (20%-80%). Humidity affects the hydrolysis rate of ethephon and the activity of natural plant extract: for every 10% increase in humidity, the ripening cycle is shortened by 5%-15%. For example, when the humidity is 20%, the avocado ripening cycle is 3.5d; when the humidity is increased to 60%, the ripening cycle is shortened to 2.0d, and the oil content of the mature avocado is increased by 1.2wt%. Suitable humidity can promote oil synthesis and improve flavor. In practical application, the humidity in the vehicle can be adjusted according to the transportation time, such as using low humidity of 30%-40% to delay ripening for long-distance transportation, and using medium humidity of 50%-60% to accelerate ripening for short-distance transportation.

[0038] As a specific embodiment of the present application, the ripening start time is adjusted by removing the film-forming layer or retaining the film-forming layer. When the film-forming layer is retained, external moisture needs to slowly penetrate to the functional layer through the air permeable hole, and the ripening reaction starts slowly, with a start time of about 36 h; after the film-forming layer is removed, the functional layer directly contacts the environmental moisture, and the ripening start time is advanced by 12-24 h, with a start time of about 12-24 h. For example, for kiwifruits with a transportation period of 5 d, the film-forming layer can be retained, so that the ripening reaction starts on the second day of transportation, and the kiwifruits are just ripe when they arrive at the destination; for bananas with a transportation period of 2 d, the film-forming layer can be removed, so that the ripening reaction starts on the day of transportation, and the bananas can be eaten when they arrive at the destination.

[0039] As a specific embodiment of the present application, the vegetables and fruits include one or more of kiwifruit, mango, banana, persimmon and avocado.

[0040] The polyphenol components and plant hormones in the natural plant extract can improve the quality of the vegetables and fruits after ripening: increase the sugar content: promote the conversion of starch to soluble sugar, so that the sugar content of the vegetables and fruits after ripening is increased by 1-3 °Brix (such as the sugar content of mango is increased from 12 °Brix to 15 °Brix); reduce the organic acid content: accelerate the decomposition of organic acids (such as citric acid and malic acid), so that the organic acid content is reduced by 0.1-0.3 wt%, and the ratio of sweet to sour is improved; maintain the color: inhibit the activity of polyphenol oxidase, and reduce browning (such as the browning rate of kiwifruit after ripening is reduced from 15% to 5%); prolong the shelf life: the antioxidant components in the natural plant extract can delay the aging process of the vegetables and fruits after ripening, and the shelf life is prolonged by 1-2 d (such as the shelf life of banana is prolonged from 3 d to 5 d).

[0041] The suitable types of vegetables and fruits include post-ripening vegetables and fruits such as kiwifruit, mango, banana, persimmon and avocado, and the vegetables and fruits can be packaged and ripened singly, or a plurality of vegetables and fruits can be mixed and ripened synchronously (by adjusting the ratio of ethephon to natural plant extract, uniform ripening of mixed vegetables and fruits is achieved, and over-ripening of certain types of vegetables and fruits is avoided).

[0042] Advantages of the present application

[0043] Synergistic improvement of ripening efficiency and safety: through the synergistic effect of natural plant extract and ethephon, the ripening efficiency is improved by 25%-40% while the amount of ethephon is reduced by 30%-40%, which not only reduces the safety risk of chemical ripening agent residues, but also solves the problem of low ripening efficiency of pure natural extract, and meets the industry development trend of "green ripening".

[0044] Overall improvement of the quality of vegetables and fruits: the natural plant extract not only improves the ripening efficiency, but also improves the sugar content, organic acid content, color and shelf life of the vegetables and fruits after ripening, solves the pain points of "ripe but not sweet" and "flavorless" caused by traditional chemical ripening, and improves the consumer experience.

[0045] Multi-dimension controllability of ripening process: through the regulation of ethylene-natural plant extract ratio, humidity regulation, and film layer state regulation, the multi-dimension controllability of ripening cycle, ripening rate, and ripening start time is realized, which adapts to the needs of different vegetables and fruits and different transportation time, and the flexibility is far superior to that of traditional ripening methods.

[0046] Integration of packaging function and industrialization adaptation: the ripening function is combined with the corrugated paper box to realize the integration of "transportation-ripening-quality improvement", and the added value of the packaging carrier is increased; the preparation process adopts dry mixing, which can seamlessly connect with the existing corrugated paper box production process without the need for additional complex equipment, and the production cost is low (the coating cost is reduced by 15%-20% per ton), which is suitable for large-scale industrial production.

[0047] Balance between packaging performance and environmental protection: the mild preparation process of the coating does not damage the structural integrity of the paperboard, and the breaking strength of the corrugated paper box coated with the coating is ≥ , and the edge pressure strength is ≥5.0 N / m, which is equivalent to the performance of the paper box without coating; the film layer can be made of degradable materials such as polylactic acid, which reduces white pollution and meets environmental protection requirements. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 It is a structure diagram of the ripening coating for vegetables and fruits.

[0049] Among them, 1 is a carrier, 2 is a connecting layer, 3 is a functional layer, and 4 is a film layer. DETAILED DESCRIPTION

[0050] The application will be further described in detail through specific examples, but the protection scope of the application is not limited to the following examples.

[0051] Example 1

[0052] A kind of preparation of ripening coating for vegetables and fruits, comprising the following steps:

[0053] (1) Functional layer preparation: weigh 25g of vinyl acetate, 0.5g of propylene glycol methyl ether acetate, 3g of plasticizer (dibutyl phthalate), 6g of ethylene, and 1g of epoxy resin, and put them into a high-speed mixer, first stir at 800r / min for 10min, then stir at 1100r / min for 10min, and the stirring temperature is 50℃, to obtain a functional layer slurry;

[0054] (2) Connecting layer coating: polyvinyl acetate glue (solid content 30wt%, viscosity ) is selected as the connecting layer material, and is coated on the surface of the paperboard for corrugated paper box by roll coating process, the coating amount is 10g / m 2 , and is dried at 60℃ for 5min to form a connecting layer;

[0055] (3) Functional layer composite: the functional layer slurry is coated on the surface of the connecting layer by means of doctor blade coating, the coating thickness is 50 μm, pre-curing at 70 °C for 10 min, and final curing at 85 °C for 10 min;

[0056] (4) Film forming layer composite: polyethylene film (film thickness 10 μm, air permeable hole diameter 1 μm, hole density 10 pieces / cm 2 ) is selected as the film forming layer, and is covered on the surface of the functional layer by means of hot pressing composite process, the hot pressing temperature is 100 °C, the pressure is 0.3 MPa, and the composite time is 5 s, to obtain the ripening coating for vegetables and fruits.

[0057] Example 2

[0058] Preparation of banana peel extract composite ripening coating, including the following steps:

[0059] (1) Natural plant extract preparation: 100 g of fresh banana peel is crushed to a particle size of 1-2 mm after washing, deionized water is added at a solid-liquid ratio of 1:10, and is extracted at 60 °C for 3 h, and then is centrifuged at 10000 r / min for 20 min, the supernatant is filtered through a 0.22 μm microporous filter, and the filtrate is vacuum concentrated at 45 °C to a solid content of 30 wt%, to obtain banana peel extract.

[0060] (2) Functional layer preparation: 25 g of vinyl acetate, 0.5 g of propylene glycol methyl ether acetate, 3 g of plasticizer (dibutyl phthalate), 6 g of ethephon, 1 g of epoxy resin, and 2 g of banana peel extract are weighed and put into a high-speed mixer; first, the vinyl acetate, propylene glycol methyl ether acetate, plasticizer, and epoxy resin are stirred at 50 °C and 800 r / min for 10 min, then the ethephon and banana peel extract are added, and the stirring speed is adjusted to 1100 r / min for 10 min, to obtain the functional layer slurry.

[0061] (3) Connecting layer coating: polyvinyl acetate glue (solid content 30 wt%, viscosity ) is selected, and is roll-coated on the surface of the paperboard for corrugated paper boxes, the coating amount is 10 g / m², and is dried at 60 °C for 5 min to form the connecting layer.

[0062] (4) Functional layer composite: the functional layer slurry is doctor blade coated on the surface of the connecting layer, the coating thickness is 50 μm, pre-curing at 70 °C for 10 min, and final curing at 85 °C for 10 min.

[0063] (5) Film forming layer composite: polyethylene film (film thickness 10 μm, air permeable hole diameter 1 μm, hole density 10 pieces / cm 2 ) is selected, and is hot pressed (100 °C, 0.3 MPa, 5 s) to obtain the ripening coating.

[0064] Example 3

[0065] Preparation of ripening coating with banana peel-mango leaf composite extract, including the following steps:

[0066] (1) Preparation of natural plant extract: Take fresh banana peel 60 g, mango leaf 40 g, wash and crush to particle size 1-2 mm, add deionized water according to solid-liquid ratio 1:12, constant temperature extraction at 65°C for 3.5h, then high speed centrifugation at 11000r / min for 22min, take the supernatant and filter through 0.3μm microporous filter membrane, vacuum concentration of the filtrate at 45°C to solid content 35wt%, get banana peel-mango leaf composite extract.

[0067] (2) Preparation of functional layer: take vinyl acetate 33g, propylene glycol methyl ether acetate 1.5g, plasticizer (dioctyl phthalate) 6.5g, ethephon 13g, epoxy resin 8.5g, banana peel-mango leaf composite extract 5g, put into high speed mixer; first stir vinyl acetate, propylene glycol methyl ether acetate, plasticizer, epoxy resin at 60°C, 850r / min for 10min, then add ethephon and composite extract, adjust the speed to 1150r / min and continue stirring for 15min, get functional layer slurry.

[0068] (3) Coating of connecting layer: select starch-based composite glue (solid content 40wt%, viscosity 1000mpa.s, pH 7.5, drying temperature 70°C, drying time 8min, drying method air drying), roll coating on the surface of paperboard for corrugated carton, coating amount 20g / m², 70°C drying for 8min, form connecting layer.

[0069] (4) Functional layer compounding: blade coating of functional layer slurry on the surface of connecting layer, coating thickness 100μm, first 72°C pre-curing for 12min, then 88°C final curing for 18min.

[0070] (5) Film forming layer compounding: select polypropylene film (film thickness 30μm, air permeation hole diameter 3μm, hole density 30 / cm 2 ), hot pressing compounding (120°C, 0.5MPa, 10s), get ripening coating.

[0071] Example 4

[0072] Preparation of ripening coating with mango leaf-tomato stem composite extract, including the following steps:

[0073] ​(1) Natural plant extract preparation: Take fresh mango leaves 50 g, tomato stems 50 g, wash and crush to a particle size of 2-3 mm, add deionized water at a solid-liquid ratio of 1:15, and immerse at 70°C for 4 h, then centrifuge at 12000 r / min for 25 min, take the supernatant and filter through a 0.45 μm microporous filter, and then concentrate the filtrate at 50°C under vacuum to a solid content of 40 wt%, to obtain a mango leaf-tomato stem composite extract.

[0074] (2) Functional layer preparation: weigh 41 g of vinyl acetate, 2.5 g of propylene glycol methyl ether acetate, 10 g of plasticizer (tributyl citrate: epoxy soybean oil = 1:1), 20 g of ethephon, 16 g of epoxy resin, and 8 g of mango leaf-tomato stem composite extract, and put them into a high-speed mixer; first stir the vinyl acetate, propylene glycol methyl ether acetate, plasticizer, and epoxy resin at 70°C and 900 r / min for 10 min, then add ethephon and the composite extract, adjust the speed to 1200 r / min, and continue stirring for 20 min to obtain a functional layer slurry.

[0075] (3) Connection layer coating: select water-based polyurethane glue (solid content 50 wt%, viscosity ), roll coat on the surface of the paperboard for corrugated paper boxes, coating amount 30 g / m 2 , dry at 80°C for 10 min to form a connection layer.

[0076] (4) Functional layer compounding: blade coat the functional layer slurry on the surface of the connection layer, coating thickness 150 μm, first pre-cure at 75°C for 15 min, then final cure at 90°C for 25 min.

[0077] (5) Film forming layer compounding: select polylactic acid film (film thickness 50 μm, air permeation hole diameter 5 μm, hole density 50 pieces / cm²), hot press compounding (140°C, 0.8 MPa, 15 s) to obtain a ripening coating.

[0078] Effect Example 1: Synergistic ripening effect of ethephon and natural plant extract (take mango as an example)

[0079] Using the preparation method of Example 3, adjust the amount of natural plant extract (banana peel-mango leaf composite extract) and ethephon, and prepare 5 groups of ripening coatings, and the amount of other raw materials remains unchanged; coat each group of coatings on the inner surface of a corrugated paper box with a size of 30 cm x 20 cm x 20 cm, put 2 kg of the same batch of seven mature mangoes into each group of paper boxes, and place them in an environment with a temperature of 25°C and a humidity of 40%, record the ripening period, sugar content and organic acid content after ripening, and the results are shown in Table 1.

[0080] Table 1 Influence of different ethephon contents on mango ripening period

[0081]

[0082] As can be seen from Table 1, with the increase of the amount of natural plant extract and the decrease of the amount of ethylene, the ripening period is significantly shortened, and the ripening efficiency is improved (the ripening period of the experimental group 4 is shortened by 59.4% compared with the control group), proving that there is a synergistic ripening effect between the two; the sugar content of the mature mango in the experimental group is increased by 1.4-3.1 °Brix compared with the control group, and the organic acid content is reduced by 0.07-0.27 wt%, indicating that the natural plant extract can effectively improve the flavor quality of mango.

[0083] Effect Example 2: Influence of Different Natural Plant Extracts on the Ripening Effect of Kiwi

[0084] The preparation method of Example 3 was used, and banana peel extract, mango leaf extract, tomato stem extract, and banana peel-mango leaf composite extract (3:2) were respectively selected as natural plant extracts (the amount was 5 g), and the amount of ethylene was 13 g, and the amounts of other raw materials were unchanged; four groups of ripening coatings were prepared and coated on the inner surface of the corrugated paper box, 2 kg of seven mature kiwi fruits were put in, and the ripening period and the browning rate of the fruits after ripening were recorded in an environment with a temperature of 25°C and a humidity of 40%, and the results are shown in Table 2.

[0085] Table 2: Influence of Different Natural Plant Extracts on the Ripening Effect of Kiwi

[0086]

[0087] As can be seen from Table 2, all four natural plant extracts can shorten the ripening period of kiwi, and the ripening efficiency of the composite extract is the highest (14.3%-23.5% shorter than that of the single extract), indicating that the combination of different extracts can enhance the synergistic effect; the browning rate of the kiwi after ripening in the composite extract group is the lowest (5.3%), which is significantly lower than that in the single extract group, proving that the antioxidant and anti-browning effect of the composite extract is better.

[0088] Effect Example 3: Influence of Humidity on the Ripening Effect and Quality of Avocado

[0089] The ripening coating prepared in Example 3 (ethylene 13 g + banana peel-mango leaf composite extract 5 g) was coated on the inner surface of the corrugated paper box, 2 kg of seven mature avocados were put in, and the ripening period and the oil content of the avocados after ripening were recorded in an environment with a temperature of 25°C and different humidities (20%, 30%, 40%, 50%, 60%), and the results are shown in Table 3.

[0090] Table 3: Influence of Humidity on the Ripening Effect and Quality of Avocado

[0091]

[0092] From Table 3, it can be seen that as the humidity increases, the ripening period of avocado gradually shortens, and the ripening period shortens by 5.9%-20.0% for every 10% increase in humidity, indicating that humidity can effectively regulate the ripening rate; when the humidity is increased to 40%-60%, the oil content of the mature avocado reaches 16.5%-17.5wt%, proving that appropriate humidity not only accelerates ripening, but also promotes oil synthesis and improves quality.

[0093] Effect Example 4: Effect of film layer state on banana ripening start time and shelf life

[0094] The ripening coating prepared in Example 3 (ethephon 13g + banana peel-mango leaf composite extract 5g) was divided into two groups: one group retained the film layer, and the other group removed the film layer; coated on the inner surface of the corrugated paper box, 2kg of seven mature bananas were loaded, and placed in an environment with a temperature of 25℃ and a humidity of 40%, the ripening start time, ripening period and shelf life after ripening (from ripening to rotting) were recorded, and the results are shown in Table 4.

[0095] Table 4 Effect of film layer state on banana ripening

[0096]

[0097] From Table 4, it can be seen that after removing the film layer, the banana ripening start time is advanced by 24h, and the ripening period is shortened by 0.6d, which can meet the rapid ripening demand of short-distance transportation; the shelf life of bananas after ripening with the film layer is extended by 0.4d, the reason is that the film layer can slow down the contact between the bananas after ripening and the external oxygen, delaying oxidation and aging.

[0098] Effect Example 5: Effect of coating on the performance and environmental friendliness of the paper box

[0099] The blank corrugated paper box without coating (control group) and the corrugated paper box coated with the coating prepared in Example 3 (experimental group) were selected to detect their mechanical properties; at the same time, the degradation performance test was conducted on the polylactic acid film layer used in the experimental group (according to GB / T 41010-2021 standard), and the results are shown in Table 5.

[0100] Table 5 Effect of coating on the performance and environmental friendliness of the paper box

[0101]

[0102] From Table 5, it can be seen that the bursting strength and edge compression strength of the paper box in the experimental group are basically the same as those in the control group (difference≤2%), indicating that the coating does not affect the load protection performance of the paper box; the 60d degradation rate of the polylactic acid film layer reaches 85.3%, meeting the environmental protection requirements, and can reduce the pollution of packaging waste to the environment.

[0103] The application forms a synergistic ripening effect with ethylene by adding natural plant extracts in the functional layer, reduces the use of chemical ripening agent, reduces the safety risk, and significantly improves the ripening efficiency (the ripening period is shortened by 25%-59%); at the same time, the natural plant extracts can improve the sugar content, organic acid content and color of the ripened vegetables and fruits, and improve the consumer experience. In addition, the humidity control and film layer state adjustment realize the multi-dimensional controllability of the ripening process, adapt to the transportation needs of different vegetables and fruits; the coating preparation process is simple, can be connected with the existing paper box production process, and does not affect the performance of the paper box, has practicality and environmental protection, and has wide industrialization application prospect.

[0104] The above examples are only used to illustrate the technical solutions of the present application, and are not limited to the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A ripening coating for vegetables and fruits, characterized by, The vegetable and fruit ripening coating comprises a connecting layer, a functional layer and a film-forming layer arranged in sequence. The connecting layer is used for connecting the carrier and the functional layer. The functional layer is composed of the following raw materials in parts by weight: vinyl acetate 25-41 parts by weight, propylene glycol methyl ether acetate 0.5-2.5 parts by weight, plasticizer 3-10 parts by weight, ethephon 6-20 parts by weight, and epoxy resin 1-16 parts by weight. The film-forming layer is used for protecting the functional layer.

2. The fruit and vegetable ripening coating according to claim 1, characterized in that, The functional layer further comprises natural plant extract 2-8 parts by weight; preferably, the natural plant extract is one or more of banana peel extract, mango leaf extract, and tomato stem extract. And / or, the connecting layer is a water-based environment-friendly glue; preferably, the water-based environment-friendly glue comprises polyvinyl acetate glue, water-based polyurethane glue, starch-based composite glue; more preferably, the water-based environment-friendly glue has a solid content of 30-50wt%, a viscosity of 30-50s / 25g (25℃) and a pH value of 7-9. (25℃); And / or, the film-forming layer is a polyvinyl chloride film, a polyethylene film, a polypropylene film, or a polylactic acid film, with a film thickness of 10-50 μm, and a surface of the film-forming layer is provided with air-permeable holes with a diameter of 1-5 μm and a density of 10-50 per cm 2 ; The plasticizer is one or more of dibutyl phthalate, dioctyl phthalate, tributyl citrate, and epoxy soybean oil. The carrier is a paperboard, preferably a corrugated carton.

3. A method for preparing the fruit ripening coating according to claim 1 or 2, characterized in that The dry mixing method comprises the following steps: (1) Preparation of the functional layer: weigh the vinyl acetate, propylene glycol methyl ether acetate, plasticizer, ethephon, and epoxy resin, and mix them at a temperature of 50-70℃ and a rotation speed of 800-1200r / min for 15-30min to obtain a functional layer slurry; (2) Coating of the connecting layer: uniformly coat the connecting layer material on the surface of the carrier, with a coating amount of 10-30g / m², and then dry at 60-80℃ for 5-10min to form the connecting layer; (3) Functional layer compounding: cover the functional layer slurry prepared in step (1) on the surface of the connecting layer by means of doctor blade coating, with a coating thickness of 50-150μm, and then solidify at 70-90℃ for 20-40min; (4) Film-forming layer compounding: cover the film-forming layer on the surface of the solidified functional layer by means of hot pressing, with a hot pressing temperature of 100-140℃, a pressure of 0.3-0.8MPa, and a compounding time of 5-15s, to obtain the vegetable and fruit ripening coating.

4. The production method according to claim 3, characterized by, The natural plant extract is added in step (1); the addition process of the natural plant extract is as follows: first mix the vinyl acetate, propylene glycol methyl ether acetate, plasticizer, and epoxy resin, and then add the ethephon and natural plant extract and continue mixing.

5. The preparation method according to claim 4, characterized in that, The mixing process in step (1) adopts a segmented stirring mode: first stir at a rotation speed of 800-900r / min for 10-20min, and then stir at a rotation speed of 1100-1200r / min for 10-20min; The solidification process in step (3) is divided into two stages: first pre-solidify at 70-75℃ for 10-15min, and then finally solidify at 85-90℃ for 10-25min.

6. Use of the vegetable and fruit ripening coating of claim 1 or 2 or the vegetable and fruit ripening coating prepared by the preparation method of any one of claims 3-5 in the transportation of vegetables and fruits.

7. Use according to claim 6, characterized in that, By adjusting the weight content of ethylene and the weight content of natural plant extract in the functional layer, the ripening cycle is regulated to 0.3-4.5 days; preferably, when the content of natural plant extract increases by 1 weight part, the amount of ethylene used can be reduced by 0.8-1.2 weight parts, and the ripening cycle is shortened by 8%-12%, to adapt to different ripening needs of vegetables and fruits.

8. Use according to claim 6, characterized in that, By adjusting the humidity of the transportation environment to 20%-80%, the ripening rate is regulated; preferably, for every 10% increase in humidity, the ripening cycle is shortened by 5%-15%.

9. Use according to claim 6, characterized in that, By removing the film-forming layer or retaining the film-forming layer, the ripening start time is adjusted, and after removing the film-forming layer, the ripening start time is advanced by 12-24 hours.

10. Use according to any one of claims 6 to 9, characterized in that, The vegetables and fruits include one or more of kiwi, mango, banana, persimmon, avocado; And / or, the natural plant extract and ethylene synergistically improve the sugar content of the vegetables and fruits after ripening by 1-3 °Brix, reduce the organic acid content by 0.1-0.3 wt%, and improve the flavor quality of the vegetables and fruits.

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