Fruit and vegetable postharvest preservative and application thereof

Abstract

The invention relates to the technical field of fruit and vegetable postharvest fresh keeping, in particular to a fruit and vegetable postharvest fresh keeping agent and application thereof.The fruit and vegetable postharvest fresh keeping agent comprises an asparagus tea extract, and a preparation method of the asparagus tea extract comprises the following steps that S1, extraction is conducted, asparagus tea and deionized water are mixed, ultrasonic extraction is conducted, then filtration is conducted, and an extracting solution is obtained; s2, concentration: concentrating the extracting solution to obtain a concentrated solution; s3, drying: freeze-drying the concentrated solution to obtain the asparagus tea extract. The fruit and vegetable postharvest preservative provided by the invention is safe and non-toxic, and can inhibit the ethylene release peak, delay the ripening and aging of fruits and vegetables such as strawberries and peaches, well maintain the appearance and hardness of the fruits and vegetables, and prolong the shelf life.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of postharvest preservation of fruits and vegetables, and in particular to a postharvest preservative for fruits and vegetables and application thereof. BACKGROUND

[0002] China is a big country of fruit and vegetable production. In recent years, with the improvement of market demand and production technology, the yield of fruits and vegetables has increased significantly. According to relevant data, the yield of fruits and vegetables in 2010 exceeded 600 million tons, and the yield of fruits in 2024 exceeded 330 million tons, and the yield of vegetables reached 860 million tons. Due to the relatively concentrated maturity period of fruit and vegetable products and the generally long distance between production and consumption, this physical isolation between production and consumption causes the contradiction between supply and demand in the market to become increasingly apparent, and improving the storage and transportation time of fruits and vegetables becomes an important way to alleviate this contradiction. According to incomplete statistics, the economic loss caused by the rotting of fruits and vegetables due to microbial infection during the storage and transportation process exceeds 70 billion yuan. Therefore, it is of great significance to explore the postharvest preservation method of fruits and vegetables.

[0003] For a long time, chemical preservatives have been considered as one of the most effective measures to control postharvest diseases of fruits and vegetables due to their high efficiency, low cost and convenience of use. However, although such chemical preservatives have been widely used in the field of fruit and vegetable preservation, the potential threat of their residues to food safety cannot be ignored. Studies have shown that chemical synthetic substances can not only have a negative impact on human health, but also have potential risks of carcinogenicity, teratogenicity and mutagenicity.

[0004] Therefore, how to provide a safer postharvest preservative for fruits and vegetables is a technical problem to be solved in the art. SUMMARY

[0005] In view of the above deficiencies in the prior art, the purpose of the present application is to provide a postharvest preservative for fruits and vegetables and application thereof. The postharvest preservative for fruits and vegetables provided by the present application is safe and non-toxic, can inhibit the ethylene release peak, delay the maturation and senescence of fruits and vegetables such as strawberries and peaches, better maintain the appearance and hardness of fruits and vegetables, and prolong the shelf life.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions: In a first aspect, the present application provides a postharvest preservative for fruits and vegetables, which comprises asparagus tea extract.

[0007] Further, the preparation method of the asparagus tea extract comprises the following steps: S1, extraction: mixing asparagus tea with deionized water, ultrasonic extraction, and then filtering to obtain an extraction liquid; S2, concentration: concentrating the extraction liquid to obtain a concentrated liquid; S3. Drying: The concentrate is freeze-dried to obtain the asparagus tea extract.

[0008] Furthermore, the mass ratio of the asparagus tea to the volume of the deionized water is 1:(10~50)g / mL; And / or, the ultrasonic extraction temperature is 10~60℃, the ultrasonic extraction power is 100-300W, and the ultrasonic extraction time is 10-60 minutes; And / or, the ultrasonic extraction is performed once; And / or, in step S1, filter paper with a pore size of 10-15 μm is used for filtration; And / or, in step S2, the extract is concentrated using a rotary evaporator; And / or, in step S2, the concentration temperature is 50–60°C; And / or, in step S2, the volume ratio of the concentrate to the extract is 1:(20-30).

[0009] Furthermore, the preparation method of the asparagus tea includes the following steps: (1) Raw material pretreatment: After washing the fresh asparagus, cut it to obtain asparagus segments; (2) Blanching and surface drying: Blanch the asparagus segments in boiling water, then cool and air dry them to evaporate surface moisture; (3) Kneading: Knead the dried asparagus sections; (4) Drying: The kneaded asparagus segments are dried to obtain the asparagus tea.

[0010] Furthermore, the fresh asparagus includes at least one of fresh green asparagus and fresh white asparagus; And / or, in step (2), the hot ironing time is 20-40 seconds; And / or, in step (2), the blanched asparagus pieces are cooled to room temperature with cold water; And / or, in step (2), the cooled asparagus pieces are spread out in a ventilated place to dry in order to evaporate the surface moisture; And / or, in step (3), the kneading time is 20-40 min and the kneading speed is 20-40 rpm; And / or, in step (4), the drying process includes initial drying and re-drying, wherein the initial drying includes drying the kneaded asparagus segments at 100-120℃ to a moisture content of 10-30wt%; and the re-drying includes re-drying the initially dried asparagus segments at 80-100℃ for 30-50min.

[0011] Secondly, the present invention provides an application of the postharvest preservative for fruits and vegetables as described in the first aspect in the postharvest preservation of fruits and vegetables.

[0012] Furthermore, the application includes the following steps: The postharvest preservative for fruits and vegetables is dissolved in a solvent to obtain a preservation solution. The postharvest fruits and vegetables to be preserved are then brought into contact with the preservation solution for preservation treatment. Alternatively, the postharvest preservative for fruits and vegetables can be prepared into a preservation film, and then the postharvest fruits and vegetables to be preserved can be wrapped with the preservation film.

[0013] Furthermore, the solvent includes deionized water; And / or, the mass ratio of the fruit and vegetable postharvest preservative to the volume of the solvent is 1:(1-15)mg / mL; And / or, the contact between the post-harvest fruits and vegetables to be preserved and the preservation solution includes: applying the preservation solution to the post-harvest fruits and vegetables to be preserved by means of soaking, spraying or smearing; And / or, the step of contacting the post-harvest fruits and vegetables to be preserved with the preservation solution for preservation treatment includes: after contacting the post-harvest fruits and vegetables to be preserved with the preservation solution, air-drying them naturally at room temperature, and then storing them; And / or, the step of preparing the postharvest preservative of fruits and vegetables into a preservation film includes: Preparation of film-forming solution: Dissolve chitosan in acidic aqueous solution, stir until completely dissolved, add plasticizer and the post-harvest preservative of fruits and vegetables, mix evenly, and let stand to degas to obtain film-forming solution; Film formation and drying: The film-forming liquid is cast onto a substrate to obtain a wet film. After drying the wet film, it is peeled off to obtain the preservation film.

[0014] Furthermore, the acidic aqueous solution includes at least one of acetic acid aqueous solution, citric acid aqueous solution, and malic acid aqueous solution; And / or, the mass ratio of the chitosan to the volume of the acidic aqueous solution is (1-3): 100 g / mL; And / or, the plasticizer includes glycerin; And / or, the volume ratio of the plasticizer to the acidic aqueous solution is (1-3):100; And / or, the mass ratio of the postharvest preservative to the volume of the acidic aqueous solution is (1-5): 100 mg / mL; And / or, the substrate includes a glass plate; And / or, the thickness of the wet film is 1-5 mm; And / or, in the film-forming and drying steps, the drying temperature is 40-60℃ and the drying time is 3-5h.

[0015] Furthermore, the fruits and vegetables include at least one of berries and stone fruits.

[0016] Compared with the prior art, the beneficial effects of the present invention include at least one of the following: (1) The postharvest preservative for fruits and vegetables provided by the present invention is safe and non-toxic, and can inhibit the release of ethylene. Peak ripening delays the ripening and senescence of fruits and vegetables such as strawberries and peaches, better maintaining their appearance and firmness, and extending their shelf life.

[0017] (2) The postharvest preservative for fruits and vegetables provided by the present invention can delay the decay of fruits and vegetables such as strawberries and peaches by inhibiting the growth of putrefactive bacteria (such as Sclerotinia sclerotiorum).

[0018] (3) This invention significantly improves the safety and antibacterial efficacy of asparagus tea extract in the preparation of a preservation film, effectively addressing the problem of post-harvest losses of fruits and vegetables. While traditional chemical preservatives are highly efficient and inexpensive, they pose risks of residual hazards and inducing drug resistance. This invention uses natural asparagus tea extract as its core ingredient, whose abundant active components have broad-spectrum antibacterial and antioxidant effects, specifically inhibiting common microorganisms that cause fruit and vegetable rot. Combined with the film-forming and antibacterial properties of chitosan itself, the two work synergistically to form a dual physical and biochemical barrier. This composite film effectively delays spoilage caused by microbial infection—which is of great significance for reducing the post-harvest loss rate of fruits and vegetables in my country, ensuring food safety and consumer health.

[0019] (4) The postharvest preservative for fruits and vegetables provided by this invention embodies the direction of green and sustainable preservation technology and has broad application prospects. The preservative provided by this invention is applied to the surface of fruits and vegetables by coating or wrapping, which is convenient to operate and can adapt to the storage and transportation chain from the production area to the consumer. The asparagus tea extract can be configured as a preservative to directly treat fruits and vegetables, or it can be prepared into a biodegradable preservation film to meet the needs of various postharvest treatment scenarios. It can not only extend the shelf life and alleviate the supply and demand contradiction caused by the isolation of production and sales areas, but also better maintain the appearance, firmness and nutritional quality of fruits and vegetables. Compared with developed countries that have controlled the loss rate of fruits and vegetables to below 5%, this invention provides a practical and feasible path for my country to develop efficient and safe preservation solutions using local natural resources, which has positive value for promoting industrial loss reduction and efficiency improvement and transformation and upgrading. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 Comparison of Sclerotinia sclerotiorum colony diameters after treatment with white asparagus tea extract and green asparagus tea extract (blank control, white asparagus tea extract, and green asparagus tea extract). Figure 2 Comparison of Sclerotinia sclerotiorum colony phenotypes after treatment with blank control, white asparagus tea extract, and green asparagus tea extract; Figure 3 The graph shows the effects of a blank control, a 1 mg / mL white asparagus tea extract preservative solution, and a 1 mg / mL green asparagus tea extract preservative solution on the storage quality of peaches. In the graph, A is the trend of ethylene release rate in each group, B is the trend of peach firmness in each group, and C is the trend of fruit brightness data in each group. Figure 4 The graphs show the effects of chitosan membrane, white asparagus tea extract composite membrane, and green asparagus tea extract composite membrane on the storage quality of strawberry fruit. In the graphs, A is the trend of ethylene release rate for each group, B is the trend of fruit firmness for each group, and C is the trend of fruit brightness for each group. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Process parameters in the following embodiments that do not specify specific conditions are generally based on conventional conditions, unless otherwise specified, indicating that all raw materials are commercially available or commonly used in this industry.

[0023] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0024] In a first aspect, the present invention provides a postharvest preservative for fruits and vegetables, the postharvest preservative for fruits and vegetables including asparagus tea extract.

[0025] The postharvest preservative for fruits and vegetables provided by this invention is safe and non-toxic. It can delay the ripening, aging and decay of fruits and vegetables such as strawberries and peaches by inhibiting the peak release of ethylene and the growth of putrefactive bacteria (such as Sclerotinia sclerotiorum). It can better maintain the appearance and firmness of fruits and vegetables and extend their shelf life.

[0026] Asparagus tea extract has shown great potential as a novel postharvest preservative for fruits and vegetables in controlling postharvest diseases and extending shelf life. This type of preservative has both antibacterial and disease-preventing effects and is safe and non-toxic. It also has excellent antioxidant and antibacterial properties, which are of great value in maintaining the postharvest quality and food safety of fruits and vegetables.

[0027] In one optional embodiment of the above-mentioned postharvest preservatives for fruits and vegetables, the preparation method of the asparagus tea extract includes the following steps: S1. Extraction: Mix asparagus tea with deionized water, perform ultrasonic extraction, and then filter to obtain the extract; S2. Concentration: The extract is concentrated to obtain a concentrated solution; S3. Drying: The concentrate is freeze-dried to obtain the asparagus tea extract.

[0028] In the above-mentioned postharvest preservatives for fruits and vegetables, as an optional embodiment, the mass ratio of the asparagus tea to the volume of the deionized water is 1:(10~50) g / mL, for example, it can be 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45 or 1:50.

[0029] In the above-mentioned postharvest preservatives for fruits and vegetables, as an optional embodiment, the ultrasonic extraction temperature is 10~60℃ (e.g., 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃ or 60℃), the ultrasonic extraction power is 100-300W (e.g., 100W, 150W, 200W, 250W or 300W), and the ultrasonic extraction time is 10-60 minutes (e.g., 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes or 60 minutes).

[0030] In the above-mentioned postharvest preservatives for fruits and vegetables, as an optional implementation, the ultrasonic extraction is performed once.

[0031] In the above-mentioned postharvest preservatives for fruits and vegetables, as an optional implementation, in step S1, filter paper with a pore size of 10-15μm is used for filtration.

[0032] In the above-mentioned postharvest preservatives for fruits and vegetables, as an optional implementation, in step S2, the extract is concentrated using a rotary evaporator.

[0033] In the above-mentioned postharvest preservatives for fruits and vegetables, as an optional implementation, in step S2, the concentration temperature is 50-60°C, for example, 50°C, 52°C, 54°C, 56°C, 58°C or 60°C.

[0034] In the above-mentioned postharvest preservatives for fruits and vegetables, as an optional implementation, in step S2, the volume ratio of the concentrate to the extract is 1:(20-30), for example, 1:20, 1:22, 1:25, 1:28, or 1:30.

[0035] As an optional implementation method of the above-mentioned postharvest preservatives for fruits and vegetables, the preparation method of the asparagus tea includes the following steps: (1) Raw material pretreatment: After washing the fresh asparagus, cut it to obtain asparagus segments; (2) Blanching and surface drying: Blanch the asparagus segments in boiling water, then cool and air dry them to evaporate surface moisture; (3) Kneading: Knead the dried asparagus sections; (4) Drying: The kneaded asparagus segments are dried to obtain the asparagus tea.

[0036] In the above-mentioned postharvest preservatives for fruits and vegetables, as an optional implementation, the fresh asparagus includes at least one of fresh green asparagus and fresh white asparagus, preferably green asparagus. Asparagus tea extract prepared from green asparagus has a better preservation effect on harvested fruits and vegetables.

[0037] In the above-mentioned postharvest preservatives for fruits and vegetables, as an optional implementation, in step (2), the blanching time is 20-40s, for example, 20s, 25s, 30s, 35s or 40s.

[0038] In the above-mentioned postharvest preservatives for fruits and vegetables, as an optional implementation method, in step (2), the blanched asparagus segments are cooled to room temperature with cold water.

[0039] In the above-mentioned postharvest preservatives for fruits and vegetables, as an optional implementation method, in step (2), the cooled asparagus segments are spread out in a ventilated place to dry in order to evaporate the surface moisture.

[0040] In the above-mentioned postharvest preservatives for fruits and vegetables, as an optional implementation, in step (3), the kneading treatment time is 20-40 minutes, for example, 20 minutes, 25 minutes, 30 minutes, 35 minutes or 40 minutes, and the kneading treatment speed is 20-40 revolutions per minute, for example, 20 revolutions per minute, 25 revolutions per minute, 30 revolutions per minute, 35 revolutions per minute or 40 revolutions per minute.

[0041] In the above-mentioned postharvest preservatives for fruits and vegetables, as an optional implementation, in step (4), the drying treatment includes initial drying and re-drying. The initial drying includes drying the kneaded asparagus segments at 100-120℃ (e.g., 100℃, 105℃, 110℃, 115℃ or 120℃) until the moisture content is 10-30wt% (e.g., 10wt%, 15wt%, 20wt%, 25wt% or 30wt%). The re-drying includes re-drying the initially dried asparagus segments at 80-100℃ (e.g., 80℃, 85℃, 90℃, 95℃ or 100℃) for 30-50 minutes (e.g., 30 minutes, 35 minutes, 40 minutes, 45 minutes or 50 minutes). Initial drying (high-temperature rapid drying) can quickly inactivate enzymes (such as polyphenol oxidase). If not inhibited rapidly at high temperatures, these enzymes will catalyze the oxidative browning of polyphenols and other substances, consuming a large amount of valuable preservative components, leading to a decrease in the antioxidant capacity of the extract and affecting the preservation effect. Re-drying (low-temperature slow drying): After the enzymes have been inactivated, the remaining moisture is slowly removed at a lower temperature. This avoids the destruction of heat-sensitive active ingredients (such as some volatile antibacterial substances and certain vitamins) by prolonged high temperatures, allowing these "preservative factors" to be fully preserved.

[0042] Secondly, the present invention provides an application of the postharvest preservative for fruits and vegetables as described in the first aspect in the postharvest preservation of fruits and vegetables.

[0043] In the above application, as an optional implementation, the application includes the following steps: The postharvest preservative for fruits and vegetables is dissolved in a solvent to obtain a preservation solution. The postharvest fruits and vegetables to be preserved are then brought into contact with the preservation solution for preservation treatment. Alternatively, the postharvest preservative for fruits and vegetables can be prepared into a preservation film, and then the postharvest fruits and vegetables to be preserved can be wrapped with the preservation film.

[0044] In the above applications, as an optional implementation, the solvent includes deionized water.

[0045] In the above applications, as an optional implementation, the mass ratio of the fruit and vegetable postharvest preservative to the volume of the solvent is 1:(1-15) mg / mL, for example, it can be 1:1 mg / mL, 1:3 mg / mL, 1:5 mg / mL, 1:7 mg / mL, 1:9 mg / mL, 1:11 mg / mL, 1:13 mg / mL or 1:15 mg / mL.

[0046] In the above applications, as an optional implementation, the step of contacting the post-harvest fruits and vegetables to be preserved with the preservation solution includes: applying the preservation solution to the post-harvest fruits and vegetables to be preserved by means of soaking, spraying or smearing.

[0047] In the above applications, as an optional implementation, the step of contacting the post-harvest fruits and vegetables to be preserved with the preservation solution for preservation treatment includes: after contacting the post-harvest fruits and vegetables to be preserved with the preservation solution, air-drying them naturally at room temperature, and then storing them.

[0048] In the above applications, as an optional implementation, the postharvest preservative for fruits and vegetables is prepared into a preservation film, comprising: Preparation of film-forming solution: Dissolve chitosan in acidic aqueous solution, stir until completely dissolved, add plasticizer and the post-harvest preservative of fruits and vegetables, mix evenly, and let stand to degas to obtain film-forming solution; Film formation and drying: The film-forming liquid is cast onto a substrate to obtain a wet film. After drying the wet film, it is peeled off to obtain the preservation film.

[0049] In the above applications, as an optional implementation, the acidic aqueous solution includes at least one of acetic acid aqueous solution, citric acid aqueous solution, and malic acid aqueous solution.

[0050] In the above applications, as an optional implementation, the ratio of the mass of chitosan to the volume of the acidic aqueous solution is (1-3):100 g / mL, for example, it can be 1:100 g / mL, 2:100 g / mL or 3:100 g / mL.

[0051] In the above applications, as an optional implementation, the plasticizer includes glycerin.

[0052] In the above applications, as an optional implementation, the volume ratio of the plasticizer to the acidic aqueous solution is (1-3):100, for example, it can be 1:100, 2:100 or 3:100.

[0053] In the above applications, as an optional implementation, the mass ratio of the fruit and vegetable postharvest preservative to the volume ratio of the acidic aqueous solution is (1-5):100 mg / mL, for example, it can be 1:100 mg / mL, 2:100 mg / mL, 3:100 mg / mL, 4:100 mg / mL or 5:100 mg / mL.

[0054] In the above applications, as an optional implementation, the substrate includes a glass plate.

[0055] In the above applications, as an optional implementation, the thickness of the wet film is 1-5 mm, for example, it can be 1 mm, 2 mm, 3 mm, 4 mm or 5 mm.

[0056] In the above applications, as an optional implementation, in the film-forming and drying steps, the drying temperature is 40-60℃ (e.g., 40℃, 45℃, 50℃, 55℃ or 60℃), and the drying time is 3-5h (e.g., 3h, 4h or 5h).

[0057] In the above applications, as an optional implementation, the fruits and vegetables include at least one of berries and stone fruits.

[0058] In the above applications, as an optional implementation, the berry fruit includes at least one of strawberry, blueberry, and kiwi.

[0059] In the above applications, as an optional implementation, the stone fruit includes at least one of peach, cherry, and apricot.

[0060] The present invention will now be described in further detail with reference to specific embodiments and comparative examples.

[0061] In the following embodiments and comparative examples: Fresh green asparagus: Variety No. 7, purchased from Weifang Baorun Food Co., Ltd. (Shandong Province, China).

[0062] Fresh white asparagus: Champion variety, purchased from Weifang Baorun Food Co., Ltd. (Shandong Province, China).

[0063] Example 1: Preparation of Green Asparagus Tea Extract as a Postharvest Preservative for Fruits and Vegetables The postharvest preservative for fruits and vegetables provided in this embodiment is green asparagus tea extract. The preparation method of the green asparagus tea extract includes the following steps: (1) Preparation of green asparagus tea: After rinsing fresh green asparagus several times with running water, cut it to obtain asparagus segments; blanch the asparagus segments in boiling water at 100℃ for about 30 seconds, then cool them to room temperature with cold water, and then spread the asparagus segments out in a ventilated place to dry in order to evaporate the surface moisture; place the dried asparagus segments in a kneading machine (type 25) and knead them at a speed of 30 r / min for 30 minutes; dry the kneaded asparagus segments at 110℃ until the moisture content is about 20wt%, and then re-dry them in an aroma-enhancing machine at 90℃ for 40 minutes to obtain green asparagus tea.

[0064] (2) Using green asparagus tea and deionized water as raw materials, 1g of green asparagus tea was added to 30mL of deionized water and ultrasonically extracted for 30min at 55℃ and 200W power. Then, the extract was filtered with filter paper with a pore size of 10-15μm to obtain the extract.

[0065] (3) Pour the extract obtained in step (2) into a rotary evaporator and evaporate it at 55 °C to concentrate it to 1 mL to obtain a concentrated solution.

[0066] (4) The concentrate obtained in step (3) was freeze-dried by a freeze dryer (temperature 0℃, vacuum degree 7Pa, drying for 24 h) to obtain green asparagus tea extract.

[0067] Example 2: Preparation of White Asparagus Tea Extract as a Postharvest Preservative for Fruits and Vegetables The postharvest preservative for fruits and vegetables provided in this embodiment is white asparagus tea extract. The preparation method of the white asparagus tea extract includes the following steps: (1) Preparation of white asparagus tea: After rinsing fresh white asparagus several times with running water, cut it to obtain asparagus segments; blanch the asparagus segments in boiling water at 100℃ for about 30 seconds, then cool them to room temperature with cold water, and then spread the asparagus segments out in a ventilated place to dry in order to evaporate the surface moisture; place the dried asparagus segments in a rolling machine (type 25) and roll them at 30 r / min for 30 minutes; dry the rolled asparagus segments at 110℃ until the moisture content is about 20wt%, and then re-dry them at 90℃ for 40 minutes in an aroma-enhancing machine to obtain white asparagus tea.

[0068] (2) Using white asparagus tea and deionized water as raw materials, 1g of white asparagus tea was added to 30mL of deionized water and ultrasonically extracted for 30min at 55℃ and 200W power. Then, the extract was filtered with filter paper with a pore size of 10-15μm to obtain the extract.

[0069] (3) Pour the extract obtained in step (2) into a rotary evaporator and evaporate it at 55 °C to concentrate it to 1 mL to obtain a concentrated solution.

[0070] (4) The concentrate obtained in step (3) was freeze-dried by a freeze dryer (temperature 0℃, vacuum degree 7Pa, drying for 24h) to obtain white asparagus tea extract.

[0071] Example 3: Preparation of Green Asparagus Tea Extract as a Postharvest Preservative for Fruits and Vegetables The postharvest preservative for fruits and vegetables provided in this embodiment is green asparagus tea extract. The preparation method of the green asparagus tea extract is basically the same as that in Example 1. The difference is that in step (2), ultrasonic extraction is performed at 40°C and 300 W power for 50 min; in step (1), the kneaded asparagus segments are first dried at 120°C to a moisture content of 30wt%, and then re-dried at 100°C for 50 min in an aroma extractor.

[0072] Comparative Example 1 The postharvest preservative for fruits and vegetables provided in this comparative example is a fresh green asparagus extract. The preparation method of the fresh green asparagus extract includes the following steps: (1) After cutting fresh green asparagus into pieces, it was pre-cooled in a -20 ℃ refrigerator for 1 day, and then placed in a freeze dryer for freeze drying (temperature 0℃, vacuum degree 7Pa, drying for 24 h). Afterwards, the freeze-dried fresh asparagus was ground into powder by a grinder and passed through a 100-mesh sieve to obtain fresh green asparagus ultrafine powder. (2) Using fresh green asparagus ultrafine powder and deionized water as raw materials, 1g of fresh green asparagus ultrafine powder was added to 30mL of deionized water and ultrasonically extracted for 30min at 55℃ and 200W power. Then, the extract was filtered with filter paper with a pore size of 10-15μm to obtain the extract.

[0073] (3) Pour the extract obtained in step (2) into a rotary evaporator and evaporate it at 55 °C to concentrate it to 1 mL to obtain a concentrated solution.

[0074] (4) The concentrate obtained in step (3) was freeze-dried by a freeze dryer (temperature 0 ℃, vacuum degree 7 Pa, drying for 24 h) to obtain fresh green asparagus extract.

[0075] Comparative Example 2 The postharvest preservative for fruits and vegetables provided in this comparative example is a fresh white asparagus extract. The preparation method of the fresh white asparagus extract includes the following steps: (1) After cutting fresh white asparagus into pieces, it was pre-cooled in a -20 ℃ refrigerator for 1 day, and then placed in a freeze dryer for freeze drying (temperature 0 ℃, vacuum degree 7 Pa, drying for 24 hours). Afterwards, the freeze-dried fresh asparagus was ground into powder by a grinder and passed through a 100-mesh sieve to obtain fresh white asparagus ultrafine powder. (2) Using fresh white asparagus ultrafine powder and deionized water as raw materials, 1g of fresh white asparagus ultrafine powder was added to 30mL of deionized water and ultrasonically extracted for 30min at 55℃ and 200W power. Then, the extract was filtered with filter paper with a pore size of 10-15μm to obtain the extract.

[0076] (3) Pour the extract obtained in step (2) into a rotary evaporator and evaporate it at 55 °C to concentrate it to 1 mL to obtain a concentrated solution.

[0077] (4) The concentrate obtained in step (3) was freeze-dried by a freeze dryer (temperature 0℃, vacuum degree 7Pa, drying for 24 h) to obtain fresh white asparagus extract.

[0078] Application Example 1 This embodiment provides an application of a postharvest preservative for fruits and vegetables in the postharvest preservation of peaches, including the following steps: The post-harvest preservative for fruits and vegetables (green asparagus tea extract) provided in Example 1 was dissolved in deionized water to obtain a preservation solution. The concentration of the post-harvest preservative in the preservation solution was 1 mg / mL. The preservation solution was evenly sprayed onto the surface of the peaches to be preserved using a spraying device until the surface of the peaches was dripping with water. Then, the peaches were naturally air-dried at room temperature to obtain the preserved peaches, which were then stored at room temperature.

[0079] Application Example 2 This embodiment provides an application of a postharvest preservative for fruits and vegetables in the postharvest preservation of peaches, including the following steps: The post-harvest preservative for fruits and vegetables (white asparagus tea extract) provided in Example 2 was dissolved in deionized water to obtain a preservation solution. The concentration of the post-harvest preservative in the preservation solution was 1 mg / mL. The preservation solution was evenly sprayed onto the surface of the peaches to be preserved using a spraying device until the surface of the peaches was dripping with water. Then, the peaches were naturally air-dried at room temperature to obtain the preserved peaches, which were then stored at room temperature.

[0080] Application Example 3 This embodiment provides an application of a postharvest preservative for fruits and vegetables in the postharvest preservation of strawberries, including the following steps: (1) Accurately weigh 1.0 g of chitosan, dissolve it in 100 mL of 1% (volume percentage) acetic acid aqueous solution, stir magnetically until completely dissolved, add 1.5 mL of glycerol as plasticizer, then add 1 mg of the postharvest preservative for fruits and vegetables (green asparagus tea extract) provided in Example 1, mix evenly and let stand to degas, and obtain film-forming solution.

[0081] (2) The film-forming liquid obtained in step (1) is cast onto a glass plate to obtain a wet film. The thickness of the wet film is controlled to be 1.0 mm. Then, it is placed in a 50 ℃ forced-air drying oven to dry for 4 h. After peeling off the film, it is cut into 10×10 cm sizes to obtain a plastic wrap. It is sealed and stored for later use.

[0082] (3) Wrap the harvested strawberry fruits with the plastic wrap obtained in step (2) to obtain the strawberry fruits after preservation treatment, and then store them at room temperature.

[0083] Application Example 4 This embodiment provides an application of a postharvest preservative for fruits and vegetables in the postharvest preservation of strawberries, including the following steps: (1) Accurately weigh 1.0 g of chitosan, dissolve it in 100 mL of 1% (volume percentage) acetic acid aqueous solution, stir magnetically until completely dissolved, add 1.5 mL of glycerol as a plasticizer, then add 1 mg of the postharvest preservative for fruits and vegetables (white asparagus tea extract) provided in Example 2, mix evenly and let stand to degas, and obtain film-forming solution.

[0084] (2) The film-forming liquid obtained in step (1) is cast onto a glass plate to obtain a wet film. The thickness of the wet film is controlled to be 1.0 mm. Then, it is placed in a 50 ℃ forced-air drying oven to dry for 4 h. After peeling off the film, it is cut into 10×10 cm sizes to obtain a plastic wrap. It is sealed and stored for later use.

[0085] (3) Wrap the harvested strawberry fruits with the plastic wrap obtained in step (2) to obtain the strawberry fruits after preservation treatment, and then store them at room temperature.

[0086] Application Comparative Example 1 This embodiment provides an application of plastic wrap in post-harvest preservation of strawberries, including the following steps: (1) Accurately weigh 1.0 g of chitosan, dissolve it in 100 mL of 1% (volume percentage) acetic acid aqueous solution, stir magnetically until completely dissolved, add 1.5 mL of glycerol as plasticizer, mix evenly and let stand to degas, and obtain film-forming solution.

[0087] (2) The film-forming liquid obtained in step (1) is cast onto a glass plate to obtain a wet film. The thickness of the wet film is controlled to be 1.0 mm. Then, it is placed in a 50 ℃ forced-air drying oven to dry for 4 h. After peeling off the film, it is cut into 10×10 cm sizes to obtain a plastic wrap. It is sealed and stored for later use.

[0088] (3) Wrap the harvested strawberry fruits with the plastic wrap obtained in step (2) to obtain the strawberry fruits after preservation treatment, and then store them at room temperature.

[0089] Performance testing 1. In vitro antibacterial experiment of asparagus tea extract This experiment verified the inhibitory effect of asparagus tea extract preservative on the mycelial growth of Sclerotinias clerotiorum through in vitro antibacterial experiments.

[0090] Test strain: Sclerotinia sclerotiorum, purchased from Beina Biotechnology - Henan Provincial Industrial Microbial Strains Engineering Technology Research Center.

[0091] Culture medium preparation: Prepare potato dextrose agar (PDA) medium and autoclave it at 121℃ for 20 min before use.

[0092] Experimental methods: (1) Preparation of drug-containing plates: The green asparagus tea extract prepared in Example 1 and the white asparagus tea extract prepared in Example 2 were dissolved in deionized water to obtain preservation solutions of different concentrations. Then, the preservation solutions of different concentrations were mixed with sterile PDA culture medium at a volume ratio of 1:9 to prepare drug-containing plates with three concentration gradients of 4 mg / mL, 8 mg / mL and 16 mg / mL. Plates with the same proportion of distilled water were used as blank controls.

[0093] (2) Use a mycelium picker to pick up mycelium for inoculation and inoculate it in the center of the control group and each plate containing preservative (asparagus tea extract).

[0094] (3) Culture and observation: The inoculated plates were placed in a 25℃ constant temperature incubator and cultured in the dark for 72 h.

[0095] (4) Data measurement: The diameter of colonies in each treatment was measured using the cross-cross method, and each treatment was repeated 3 times.

[0096] Experimental results: After 72 hours of incubation, the following was observed: (1) The mycelium in the blank control group grew vigorously, and the average colony diameter reached 89 mm; (2) All treatments with asparagus tea extract at different concentrations showed significant antibacterial effects, and the antibacterial effect increased with increasing concentration. (3) When the extract concentration was 16 mg / mL, the antibacterial effect was most significant. After treatment with green asparagus tea extract, the colony diameter was only 45 mm, and the antibacterial rate reached 49.4%.

[0097] (4) Green asparagus tea extract at various concentrations showed better antibacterial effects than white asparagus tea extract. For detailed experimental results, please see... Figure 1 , Figure 2 , Figure 1 Comparison of Sclerotinia sclerotiorum colony diameters after treatment with the white asparagus tea extract prepared in Example 2 and the green asparagus tea extract prepared in Example 1 (as blank control). Figure 2 Comparison of Sclerotinia sclerotiorum colony phenotypes after treatment with white asparagus tea extract prepared in Example 2 and green asparagus tea extract prepared in Example 1, serving as a blank control.

[0098] Experimental results show that asparagus tea extract can effectively inhibit the mycelial growth of *Sclerotinia sclerotiorum*, and its antibacterial effect is more significant with higher concentrations. This provides experimental evidence for the application of asparagus tea extract as a fruit preservative.

[0099] 2. In vitro antibacterial comparison experiment of extracts from fresh asparagus and asparagus tea. Test strain: Sclerotinia sclerotiorum, purchased from Beina Biotechnology - Henan Provincial Industrial Microbial Strains Engineering Technology Research Center.

[0100] Culture medium preparation: Prepare potato dextrose agar (PDA) medium and autoclave it at 121℃ for 20 min before use.

[0101] Experimental methods: (1) Preparation of drug-containing plates: The green asparagus tea extract prepared in Example 1, the white asparagus tea extract prepared in Example 2, the fresh green asparagus extract prepared in Comparative Example 1, and the fresh white asparagus extract prepared in Comparative Example 2 were dissolved in deionized water to obtain preservation solutions. The different preservation solutions were mixed with sterile PDA culture medium at a volume ratio of 1:9 to prepare drug-containing plates with a final concentration of 8 mg / mL. Plates with the same proportion of distilled water were used as blank controls.

[0102] (2) Use a mycelium picker to pick up mycelium for inoculation and inoculate it in the center of the control group and each plate containing preservative (asparagus tea extract or fresh asparagus extract).

[0103] (3) Culture observation: The inoculated plates were placed in a 25 ℃ constant temperature incubator and cultured in the dark for 72 h.

[0104] (4) Data measurement: Pixel conversion was performed according to the scale given in the Sclerotium colony phenotypic diagram. The colony range was selected using the selection tool in Photoshop. In the analysis-measurement tool, Photoshop calculated the corresponding area according to the scale. Each treatment was repeated 3 times, and the average value of the test results was taken.

[0105] Experimental results: After 72 hours of incubation, the following was observed: (1) The mycelial growth in the blank control group was vigorous. The colony coverage area was statistically analyzed, and the colony coverage area of ​​the blank control group was 60.29 cm. 2 The colony coverage area of ​​the white asparagus tea extract group was 22.96 cm². 2 The colony coverage area of ​​the green asparagus tea extract group was 22.42 cm². 2 The colony coverage area of ​​the fresh white asparagus extract group was 30.79 cm². 2 The colony coverage area of ​​the fresh green asparagus extract group was 27.15 cm². 2 .

[0106] (2) All asparagus extracts showed significant antibacterial effects, with green asparagus showing a more significant antibacterial effect than white asparagus, and tea extract showing a more significant effect than fresh asparagus extract.

[0107] Experimental results show that both asparagus tea extract and fresh asparagus extract can effectively inhibit the mycelial growth of Sclerotinia sclerotiorum. The antibacterial effect of asparagus tea extract is more significant than that of fresh asparagus extract, which provides experimental evidence for the application of asparagus tea extract in fruit biological preservatives.

[0108] 3. Postharvest preservation experiment of peach fruit This experiment verified the preservation effect of the postharvest preservative provided by this invention on peach fruit through a postharvest preservation experiment.

[0109] Test materials: Selected peaches that are uniform in size, free from mechanical damage, pests and diseases, and harvested at a consistent maturity.

[0110] Experimental Design: The peaches were randomly divided into 3 groups, and the specific processing was as follows: Experimental Group 1: The post-harvest preservative for fruits and vegetables (green asparagus tea extract) provided in Example 1 was dissolved in deionized water to obtain a preservation solution. The concentration of the post-harvest preservative in the preservation solution was 1 mg / mL. The preservation solution was evenly sprayed onto the surface of the peaches to be preserved using a spraying device until the surface of the peaches was dripping with water. Then, the peaches were naturally air-dried at room temperature to obtain the peaches after preservation treatment. All treated fruits were labeled and then stored indoors at room temperature to observe the preservation effect.

[0111] Experimental Group 2: The post-harvest preservative for fruits and vegetables (white asparagus tea extract) provided in Example 2 was dissolved in deionized water to obtain a preservation solution. The concentration of the post-harvest preservative in the preservation solution was 1 mg / mL. The preservation solution was evenly sprayed onto the surface of the peaches to be preserved using a spraying device until the surface of the peaches was dripping with water. Then, the peaches were naturally air-dried at room temperature to obtain the peaches after preservation treatment. All treated fruits were labeled and then stored indoors at room temperature to observe the preservation effect.

[0112] Control group: Peaches were treated with an equal amount of deionized water using the same spraying device and then air-dried at room temperature. All treated fruits were labeled and then stored indoors at room temperature to observe the preservation effect.

[0113] Measurement indicators and methods: (1) Ethylene release rate: A 1L container was used to place a sample and seal it for 1 h. After sealing, headspace gas was collected using a 1ml syringe to determine the ethylene generation rate. The collected gas sample was injected into a GC-2010 gas chromatograph (Shimadzu Corporation, Kyoto, Japan) for analysis. Three ethylene release rates were measured at each collection point, and the average value of the test results was taken. Gas chromatography was then used to determine the ethylene release rate every 24 h thereafter. The ethylene release rate calculation formula followed the industry standard GH / T 1405-2022 "Determination of Ethylene Release Rate during Fruit and Vegetable Storage - Gas Chromatography": Ethylene release rate (μL / kg•h) = V × (A 样 ÷ A 标 ) ×C 标 / (m × t), where V is the remaining volume of the container, A 样 A represents the peak area of ​​ethylene gas in the sample gas. 标 The peak area of ​​standard ethylene gas, C 标 denoted as standard ethylene gas concentration, m as sample mass, and t as ethylene release time.

[0114] (2) Fruit firmness: The firmness of the fruit was measured every 24 hours using a texture analyzer. The firmness of the fruit was measured using a CT3 texture analyzer (Brookfield Engineering Laboratory, Middleborough, Massachusetts, USA). The instrument is equipped with a probe with a diameter of 2 mm and a puncture speed of 1 mm / s. Before the test, about 1 mm of peel needs to be removed and the puncture depth is 10 mm. During the storage of peaches, the firmness of 3 fruits was measured at each time point. Three equidistant points were selected at the equator for each fruit and the test results were averaged.

[0115] (3) Peel brightness: The L* value was measured every 24 h using a colorimeter. Each treatment was repeated 3 times. A colorimeter (CR-400, Konica Minolta Co., Ltd., 2018-3-1) was used. Before each measurement, a white calibration plate CR-A43 was used for calibration. Three biological replicates and three experimental replicates were set up. The equatorial part of the fruit was measured once every 1 s. There was a 3 s interval between each measurement. The color parameter L* describes the brightness of the sample. The test results were averaged. ΔL = L* (measured value) - L0 (white plate value).

[0116] Experimental results: After 5 days of storage, the measurement results for each treatment group are as follows: Figure 3 As shown, Figure 3The graphs show the effects of a blank control, 1 mg / mL white asparagus tea extract preservative solution, and 1 mg / mL green asparagus tea extract preservative solution on the storage quality of peaches. Figure A shows the trend of ethylene release rate for each group. It can be seen that the control group showed a significant peak in ethylene release on day 3, while the ethylene release rate in the experimental groups was significantly inhibited. The green asparagus tea extract group showed a more significant inhibitory effect on ethylene release, while the white asparagus extract group had a significantly lower ethylene release rate than the control group, but a slightly higher rate than the green asparagus tea extract group. Figure B shows the trend of peach fruit firmness for each group. The firmness of each treatment group gradually decreased over time, with the control group showing the fastest decrease in firmness at day 2. d represents the low hardness value. The hardness of the control group decreased significantly compared to the experimental group. Both extracts had the effect of delaying fruit softening. Among the experimental groups, the green asparagus tea extract group had the highest hardness and significantly inhibited the decrease in hardness. C is the trend graph of the changes in fruit brightness data for each group. Both asparagus tea extract treatments delayed the decrease in fruit brightness, which is beneficial to maintaining the appearance of the product. The ΔL value of the control group decreased from the initial -23.7 to -32.9, the ΔL value of the green asparagus tea extract treatment group was -28.0, and the ΔL value of the white asparagus tea extract treatment group was -27.5.

[0117] This experiment shows that asparagus tea extract treatment can effectively inhibit the peak of ethylene release in peach fruits, alleviate the decrease in fruit firmness and darkening of brightness. Among them, green asparagus tea extract has a better preservation effect than white asparagus tea extract. This provides reliable technical support for the post-harvest application of asparagus tea extract in delaying fruit senescence and softening, and extending fruit shelf life.

[0118] 4. Experiment on the application of food preservation film This experiment verified the effect of chitosan composite film on the postharvest preservation of strawberry fruits through a postharvest preservation experiment.

[0119] (1) Experimental materials: Select freshly harvested strawberry fruits that are uniform in size, consistent in maturity, and free from mechanical damage and pests.

[0120] (2) Experimental design: The strawberries were randomly divided into three groups, and the specific treatments were as follows: Experimental Group 1: The harvested strawberry fruits were wrapped with the plastic wrap (white asparagus tea extract composite film) obtained in step (2) of Application Example 4.

[0121] Experimental Group 2: The harvested strawberry fruits were wrapped with the plastic wrap (green asparagus tea extract composite film) obtained in step (2) of Application Example 3.

[0122] Control group: Strawberry fruits were wrapped with the preservation film (chitosan film) obtained in step (2) of Comparative Example 1.

[0123] (3) Storage conditions: All treated strawberry fruits were stored at a temperature of 0±1℃ and a relative humidity of 85%. Each treatment was replicated in 3 replicates, with 3 fruits per replicate.

[0124] (4) Measurement indicators and methods ① Firmness: Fruit firmness was measured using a CT3 texture analyzer (Brookfield). This instrument is equipped with a 2 mm diameter probe, a puncture speed of 1 mm / s, and a puncture depth of 4 mm. During strawberry storage, firmness was measured at each fruit at each time point. Three equidistant points were selected at the equator for each fruit, and measurements were taken every 24 hours. The average value of the test results was taken.

[0125] ② Ethylene release rate: Three samples were placed in a 0.22 L container and sealed for 1 h. After sealing, headspace gas was collected using a 1 ml syringe to determine the ethylene generation rate. The collected gas sample was injected into a GC-2010 gas chromatograph (Shimadzu Corporation, Kyoto, Japan) for analysis. Three ethylene release rates were measured at each collection point, and the average value was taken. Measurements were then taken every 24 h thereafter. The ethylene release rate was calculated according to the industry standard GH / T1405-2022 "Determination of Ethylene Release Rate during Fruit and Vegetable Storage - Gas Chromatography": Ethylene release rate (μL / kg•h) = V × (A 样 ÷ A 标 ) ×C 标 / (m × t), where V is the remaining volume of the container, A 样 A represents the peak area of ​​ethylene gas in the sample gas. 标 The peak area of ​​standard ethylene gas, C 标 denoted as standard ethylene gas concentration, m as sample mass, and t as ethylene release time.

[0126] ③ Sensory quality: The samples were placed under natural light, and the L* value was measured every 24 hours using a colorimeter (CR-400, Konica Minolta). Before each measurement, a white calibration plate (CR-A43) was used for calibration. Three biological replicates and three experimental replicates were set up, measuring the equatorial region of the fruit. Measurements were taken once every 1 second, with a 3-second interval between each measurement. The color parameter L* describes the brightness of the sample. The average value of the test results was taken, ΔL = L* (measured value) - L0 (white plate value).

[0127] (5) Experimental results: After 3 days of storage, the measurement results of each treatment group are as follows: Figure 4 As shown, Figure 4The graphs show the effects of chitosan membrane, white asparagus tea extract composite membrane, and green asparagus tea extract composite membrane on the storage quality of strawberry fruit. In the graphs, A is the trend of ethylene release rate for each group, B is the trend of fruit firmness for each group, and C is the trend of fruit brightness for each group.

[0128] Depend on Figure 4 It can be seen that: ① Changes in ethylene release rate After 3 days of storage, the results for each treatment group are as follows: The control group had the highest ethylene release rate among all experimental groups, reaching a high value at 2 days.

[0129] The experimental group showed a significantly lower ethylene release rate compared to the control group, demonstrating a significant inhibitory effect on ethylene release.

[0130] In the experimental groups, the green asparagus tea extract composite membrane group showed better inhibitory effects than the white asparagus tea extract composite membrane group during 1-2 days; the white asparagus tea extract composite membrane group showed better inhibitory effects than the green asparagus tea extract composite membrane group during 2-3 days.

[0131] ② Changes in fruit firmness: The control group showed the most significant decrease in hardness and the fastest rate of decrease. The experimental group showed a slower decrease in hardness compared to the control group, and the effect of delaying the decrease in fruit hardness was significant. Among the experimental groups, the green asparagus tea extract composite film group had the highest hardness, and the effect was more significant than that of the white asparagus tea extract composite film group.

[0132] The hardness of the control group decreased from an initial 0.52 N to 0.35 N, a decrease of 32.7%. The hardness of the green asparagus tea extract composite membrane treatment group remained at 0.45 N, with a decrease rate of only 13.5%. The hardness of the white asparagus tea extract composite membrane treatment group was 0.37 N, with a decrease rate of 28.8%.

[0133] ③ Changes in peel brightness: The ΔL value of the control group decreased from the initial -43.1 to -57.47, the ΔL value of the green asparagus tea extract composite membrane treatment group remained at -52.8, and the ΔL value of the white asparagus tea extract composite membrane treatment group was -55.2.

[0134] This experiment shows that the asparagus tea extract composite film can effectively reduce ethylene accumulation, inhibit the peak ethylene release of strawberries to a certain extent, and alleviate the decrease in fruit firmness and darkening of brightness. The effect of green asparagus tea extract composite film is significantly higher than that of white asparagus tea extract composite film, which provides reliable technical support for the application of asparagus tea composite film in strawberry fruit preservation.

[0135] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A postharvest preservative for fruits and vegetables, characterized in that, The postharvest preservatives for fruits and vegetables include asparagus tea extract.

2. The postharvest preservative for fruits and vegetables according to claim 1, characterized in that, The preparation method of the asparagus tea extract includes the following steps: S1. Extraction: Mix asparagus tea with deionized water, perform ultrasonic extraction, and then filter to obtain the extract; S2. Concentration: The extract is concentrated to obtain a concentrated solution; S3. Drying: The concentrate is freeze-dried to obtain the asparagus tea extract.

3. The postharvest preservative for fruits and vegetables according to claim 2, characterized in that, The mass ratio of the asparagus tea to the volume of the deionized water is 1:(10~50)g / mL; And / or, the ultrasonic extraction temperature is 10~60℃, the ultrasonic extraction power is 100-300W, and the ultrasonic extraction time is 10-60 minutes; And / or, the ultrasonic extraction is performed once; And / or, in step S1, filter paper with a pore size of 10-15 μm is used for filtration; And / or, in step S2, the extract is concentrated using a rotary evaporator; And / or, in step S2, the concentration temperature is 50–60°C; And / or, in step S2, the volume ratio of the concentrate to the extract is 1:(20-30).

4. The postharvest preservative for fruits and vegetables according to claim 2, characterized in that, The preparation method of the asparagus tea includes the following steps: (1) Raw material pretreatment: After washing the fresh asparagus, cut it to obtain asparagus segments; (2) Blanching and surface drying: Blanch the asparagus segments in boiling water, then cool and air dry them to evaporate surface moisture; (3) Kneading: Knead the dried asparagus sections; (4) Drying: The kneaded asparagus segments are dried to obtain the asparagus tea.

5. The postharvest preservative for fruits and vegetables according to claim 4, characterized in that, The fresh asparagus includes at least one of fresh green asparagus and fresh white asparagus; And / or, in step (2), the hot ironing time is 20-40 seconds; And / or, in step (2), the blanched asparagus pieces are cooled to room temperature with cold water; And / or, in step (2), the cooled asparagus pieces are spread out in a ventilated place to dry in order to evaporate the surface moisture; And / or, in step (3), the kneading time is 20-40 min and the kneading speed is 20-40 rpm; And / or, in step (4), the drying process includes initial drying and re-drying, wherein the initial drying includes drying the kneaded asparagus segments at 100-120℃ to a moisture content of 10-30wt%; and the re-drying includes re-drying the initially dried asparagus segments at 80-100℃ for 30-50min.

6. The application of a postharvest preservative for fruits and vegetables as described in any one of claims 1-5 in the postharvest preservation of fruits and vegetables.

7. The application according to claim 6, characterized in that, The application includes the following steps: The postharvest preservative for fruits and vegetables is dissolved in a solvent to obtain a preservation solution. The postharvest fruits and vegetables to be preserved are then brought into contact with the preservation solution for preservation treatment. Alternatively, the postharvest preservative for fruits and vegetables can be prepared into a preservation film, and then the postharvest fruits and vegetables to be preserved can be wrapped with the preservation film.

8. The application according to claim 7, characterized in that, The solvent includes deionized water; And / or, the mass ratio of the fruit and vegetable postharvest preservative to the volume of the solvent is 1:(1-15)mg / mL; And / or, the contact between the post-harvest fruits and vegetables to be preserved and the preservation solution includes: applying the preservation solution to the post-harvest fruits and vegetables to be preserved by means of soaking, spraying or smearing; And / or, the step of contacting the post-harvest fruits and vegetables to be preserved with the preservation solution for preservation treatment includes: after contacting the post-harvest fruits and vegetables to be preserved with the preservation solution, air-drying them naturally at room temperature, and then storing them; And / or, the step of preparing the postharvest preservative of fruits and vegetables into a preservation film includes: Preparation of film-forming solution: Dissolve chitosan in acidic aqueous solution, stir until completely dissolved, add plasticizer and the post-harvest preservative of fruits and vegetables, mix evenly, and let stand to degas to obtain film-forming solution; Film formation and drying: The film-forming liquid is cast onto a substrate to obtain a wet film. After drying the wet film, it is peeled off to obtain the preservation film.

9. The application according to claim 8, characterized in that, The acidic aqueous solution includes at least one of acetic acid aqueous solution, citric acid aqueous solution, and malic acid aqueous solution; And / or, the mass ratio of the chitosan to the volume of the acidic aqueous solution is (1-3): 100 g / mL; And / or, the plasticizer includes glycerin; And / or, the volume ratio of the plasticizer to the acidic aqueous solution is (1-3):100; And / or, the mass ratio of the postharvest preservative to the volume of the acidic aqueous solution is (1-5): 100 mg / mL; And / or, the substrate includes a glass plate; And / or, the thickness of the wet film is 1-5 mm; And / or, in the film-forming and drying steps, the drying temperature is 40-60℃ and the drying time is 3-5h.

10. The application according to claim 6, characterized in that, The fruits and vegetables mentioned include at least one of berries and stone fruits.

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