阅读说明：本技术 一种净菜加工方法 (Processing method of clean vegetables ) 是由 黄有侠 于 2020-12-09 设计创作，主要内容包括：本发明提供了一种净菜加工方法,其步骤主要包括采收、真空预冷、修整、清洗、切分、保鲜、脱水、包装、冷藏贮藏等工序,不仅安全高效,而且能够有效去除净菜表面微生物,更好地延长净菜的货架期,最大限度地保证了净菜的品质和营养价值。(The invention provides a clean vegetable processing method which mainly comprises the working procedures of harvesting, vacuum precooling, trimming, cleaning, cutting, fresh keeping, dehydrating, packaging, refrigerating and storing and the like, is safe and efficient, can effectively remove microorganisms on the surface of the clean vegetable, better prolongs the shelf life of the clean vegetable, and furthest ensures the quality and the nutritive value of the clean vegetable.)

1. A clean vegetable processing method is characterized by comprising the following steps:

(1) harvesting, namely harvesting vegetables meeting the harvesting quality requirement in time, and strictly controlling the quality of the vegetables;

(2) vacuum pre-cooling, namely spraying a pre-treatment liquid on the surface of the harvested vegetables, then placing the vegetables in a vacuum chamber, starting a vacuum pump and a refrigerating device, closing the vacuum pump and the refrigerating device when the temperature in the vacuum chamber is reduced to 2-5 ℃, and keeping for 40min to obtain the pre-cooled vegetables, wherein the pre-treatment liquid is a 3-6 wt% calcium chloride aqueous solution, and the spraying amount of the pre-treatment liquid is 3-8% of the mass of the harvested vegetables;

(3) trimming, namely trimming the pre-cooled vegetables to enable the edible part to reach more than 90% so as to obtain trimmed vegetables;

(4) cleaning, namely placing the trimmed vegetables in 0.8-2.5mg/L ozone water solution circularly flowing at the temperature of 2-5 ℃, and simultaneously performing ultrasonic cleaning for 6-15min under the conditions of ultrasonic frequency of 30-40KHz and ultrasonic power of 300- & lt 500 & gtW to obtain cleaned vegetables, wherein the bath ratio of the trimmed vegetables to the ozone water solution is 1g: (5-10) mL;

(5) cutting, namely cutting the cleaned vegetables into sections of 3cm, and spraying and cleaning the cleaned vegetables for 45-90s by using a vitamin C aqueous solution with the concentration of 80-150mg/L at the flow rate of 5-15L/min to obtain the cut vegetables;

(6) and (2) fresh-keeping, namely putting the cut vegetables into a water tank, immersing the cut vegetables in a circulating fresh-keeping solution at the temperature of 2-5 ℃ for 5-15min, then taking the vegetables out of the water tank under the drive of a conveying mesh belt, and spraying purified water for 15-45s at the flow rate of 5-15L/min to obtain the fresh-keeping treated vegetables, wherein the bath ratio of the cut vegetables to the fresh-keeping solution is 1g: (3-10) mL;

(7) dewatering, namely placing the vegetables subjected to fresh-keeping treatment in a centrifuge for dewatering and drying, wherein the centrifugation conditions are as follows: the rotation speed is 600-;

(8) packaging, namely putting the dehydrated vegetables into a polyethylene packaging bag with the thickness of 0.05mm, filling prepared mixed gas, and sealing the opening of the bag to obtain a packaged product, wherein the mixed gas is nitrogen and oxygen according to the volume ratio of (85-95): (5-15) the mixed gas;

(9) and (4) refrigerating and storing, namely quickly putting the packaged product into a refrigerator for storage, wherein the temperature of the refrigerator is 2-5 ℃, and the humidity is 75-85%.

2. The processing method of the clean vegetable as claimed in claim 1, wherein the fresh-keeping solution is composed of the following raw materials in parts by weight: 0.1-10 wt% of plant extract, 0.4-5 wt% of film-forming agent, 0.1-2 wt% of emulsifier and the balance of water.

3. The method for processing the clean vegetables as claimed in claim 2, wherein the preparation method of the fresh-keeping liquid is as follows: mixing the components, stirring at 20-30 ℃ and 1000rpm for 2-6 hours, and then carrying out ultrasonic treatment for 20-60min to obtain the fresh-keeping liquid, wherein the ultrasonic frequency is 30-40KHz, and the ultrasonic power is 400W and 600W.

4. The method of claim 2, wherein the plant extract is one or more of grape seed extract, spinach seed extract, lactic acid bacteria fermented spinach seed extract, and barley extract.

5. The clean vegetable processing method of claim 2, wherein the film forming agent is one or a mixture of more than two of chitosan, modified chitosan, pullulan, Ag @ CNTs-COOH @ chitosan composite material.

6. The clean vegetable processing method of claim 5, wherein the film forming agent is Ag @ CNTs-COOH @ chitosan composite material.

7. The clean vegetable processing method of claim 6, wherein the Ag @ CNTs-COOH @ chitosan composite material is prepared by the following steps:

s1, adding 1 part by weight of carbon nanotube CNTs into 80-120 parts by weight of mixed solution of concentrated sulfuric acid and concentrated nitric acid in a mass ratio of 1:1, performing ultrasonic treatment for 30-60min by using an ultrasonic cell crusher, then stirring the mixture at 100 ℃ and a rotation speed of 8000-8000 plus of rotation for condensation and reflux for 4-8h, after the reaction is finished, centrifuging for 8-15min at a rotation speed of 8000-5000 plus of rotation, washing for 4-8 times by using deionized water, placing the mixture into a vacuum drying oven, and drying for 6-24h at 50-80 ℃ to obtain CNTs-COOH;

s2, adding the CNTs-COOH obtained in the S1 and 1-5 parts by weight of silver nitrate into 20-50mL of deionized water, stirring at the rotating speed of 300-10000 rpm for 20-40min to obtain a mixed solution, then adding 2-6 parts by weight of sodium borohydride, continuing stirring for reaction for 5-10h, centrifuging at the rotating speed of 6000-10000rpm for 8-12min after the reaction is finished, washing with deionized water for 2-5 times, and freeze-drying to obtain Ag @ CNTs-COOH;

s3, adding the Ag @ CNTs-COOH obtained in the S2 into 20-50mL of deionized water to obtain a dispersion liquid A; adding 1 part by weight of chitosan into 20-50mL of 0.1mol/L acetic acid aqueous solution to obtain a solution B; and then mixing the dispersion liquid A and the solution B, carrying out ultrasonic reaction for 40-80min, centrifuging the product at the rotation speed of 4000-8000rpm for 5-15min, washing the product for 4-8 times by using deionized water, and carrying out freeze drying to obtain the Ag @ CNTs-COOH @ chitosan composite material.

8. The method for processing clean vegetables according to claim 2, wherein the emulsifier is one or a mixture of more than two of tween 20, sodium dodecyl benzene sulfonate and lauroyl arginine ethyl ester hydrochloride.

9. The method of claim 8, wherein the emulsifier is lauroyl arginine ethyl ester hydrochloride.

10. A method as claimed in any one of claims 1 to 9, wherein the vegetable is any one of leaf vegetables, rhizomes, cauliflower, fresh beans, melons and solanaceous vegetables.

Technical Field

The invention relates to the technical field of clean vegetable processing, in particular to a clean vegetable processing method.

Background

The vegetables are one of indispensable foods in the diet of people, and can supplement various vitamins and minerals required by the body. Due to the laggard state of the domestic vegetable postharvest treatment and circulation system, the problems of serious postharvest loss, urban environmental pollution, labor waste and the like of the vegetables exist. According to statistics, about 30 percent of vegetables in China are rotten and deteriorated in the processes of harvesting, storing, processing and transporting every year, the vegetable loss is up to hundreds of millions of tons, and the basic nutritional requirements of two hundred million people can be almost met. Therefore, the method has great practical significance on effectively ensuring the quality of the vegetables, inhibiting the speed of water loss, yellowing and rotting of the vegetables in the processes of storage, transportation and sale and prolonging the shelf life of the vegetables.

Clean vegetables, called 'new food of the new century revolution', are short for clean fresh vegetables, and refer to fresh vegetables which are subjected to grading, sorting, cleaning, cutting, fresh keeping, packaging and other treatments so as to keep the fresh state of the vegetables. After the consumer purchases the product, it can be consumed or cooked without further treatment. With the acceleration of modern life rhythm and the improvement of living standard, the consumption of vegetables is continuously increased, and the clean vegetables rapidly become the posttaste of the vegetable market due to the characteristics of freshness, convenience, nutrition, no public nuisance and the like.

After the vegetables are cut, epidermal tissues are damaged, so that cells are broken, water is rapidly lost, excessive water is lost, the product is wilted, shrunken and dried, and the freshness state is lost. Meanwhile, physiological and biochemical reactions such as fast respiration, aggravation of enzymatic change, non-enzymatic browning and the like can be induced, and the extravasation of tissue juice and the oxidation of some nutrient components can be caused to cause the loss of nutrient substances. Therefore, the research on how to effectively improve the quality of the clean vegetables and prolong the shelf life has important significance for improving the commodity value of the clean vegetables.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides refreshing pineapple fruit beer tea and a preparation method thereof.

In order to solve the technical problems, the invention adopts the technical scheme that:

a clean vegetable processing method is characterized by comprising the following steps:

(1) harvesting, namely harvesting vegetables meeting the harvesting quality requirement in time, and strictly controlling the quality of vegetable raw materials;

(2) vacuum pre-cooling, namely spraying a pre-treatment liquid on the surface of the harvested vegetables, then placing the vegetables in a vacuum chamber, starting a vacuum pump and a refrigerating device, closing the vacuum pump and the refrigerating device when the temperature in the vacuum chamber is reduced to 2-5 ℃, and keeping for 40min to obtain the pre-cooled vegetables, wherein the pre-treatment liquid is a 3-6 wt% calcium chloride aqueous solution, and the spraying amount of the pre-treatment liquid is 3-8% of the mass of the harvested vegetables;

(3) trimming, trimming the pre-cooled vegetables, removing yellow leaves, disease spots and vegetables with unqualified shapes, and enabling the edible part to reach more than 90% to obtain trimmed vegetables;

(4) cleaning, namely placing the trimmed vegetables in 0.8-2.5mg/L ozone water solution circularly flowing at the temperature of 2-5 ℃, and simultaneously performing ultrasonic cleaning for 6-15min under the conditions of ultrasonic frequency of 30-40KHz and ultrasonic power of 300- & lt 500 & gtW to obtain cleaned vegetables, wherein the bath ratio of the trimmed vegetables to the ozone water solution is 1g: (5-10) mL;

(5) cutting, namely cutting the cleaned vegetables into sections of 3cm, and spraying 80-150mg/L vitamin C aqueous solution at the flow rate of 10L/min for 45-90s to obtain the cut vegetables;

(6) and (2) fresh-keeping, namely putting the cut vegetables into a water tank, immersing the cut vegetables in a circulating fresh-keeping solution at the temperature of 2-5 ℃ for 5-15min, then taking the vegetables out of the water tank under the drive of a conveying mesh belt, and spraying purified water for 15-45s at the flow rate of 5-15L/min to obtain the fresh-keeping treated vegetables, wherein the bath ratio of the cut vegetables to the fresh-keeping solution is 1g: (3-10) mL;

(7) dewatering, namely placing the vegetables subjected to fresh-keeping treatment in a centrifuge for dewatering and drying, wherein the centrifugation conditions are as follows: the rotation speed is 600-;

(8) packaging, namely putting the dehydrated vegetables into a polyethylene packaging bag with the thickness of 0.05mm, filling prepared mixed gas, and sealing the opening of the bag to obtain a packaged product, wherein the mixed gas is nitrogen and oxygen according to the volume ratio of (85-95): (5-15) the mixed gas;

(9) and (4) refrigerating and storing, namely quickly putting the packaged product into a refrigerator for storage, wherein the temperature of the refrigerator is 2-5 ℃, and the humidity is 75-85%.

The fresh-keeping solution is prepared from the following raw materials in parts by weight: 0.1-10 wt% of plant extract, 0.4-5 wt% of film-forming agent, 0.1-2 wt% of emulsifier and the balance of water. The preparation method of the fresh-keeping liquid comprises the following steps: mixing the components, stirring at 20-30 ℃ and 1000rpm for 2-6 hours, and then carrying out ultrasonic treatment for 20-60min to obtain the fresh-keeping liquid, wherein the ultrasonic frequency is 30-40KHz, and the ultrasonic power is 400W and 600W.

The plant extract is one or more of grape seed extract, spinach seed extract, lactobacillus fermented spinach seed extract, and barley extract.

The plant extract is a spinach seed extract, and the preparation method of the spinach seed extract comprises the following steps: pulverizing fructus Spinaciae, sieving with 60 mesh sieve, extracting with 70 wt% ethanol at 1g (15-30) mL at 60-80 deg.C under 30-40KHz ultrasonic frequency and 500W ultrasonic power for 30-60min, filtering, collecting filtrate, and freeze drying to obtain fructus Spinaciae extract.

Preferably, the plant extract is lactobacillus fermented spinach seed extract. The preparation method of the lactobacillus fermented spinach seed extract comprises the following steps:

s1, crushing the spinach seeds, sieving the crushed spinach seeds with a 80-mesh sieve, mixing the sieved spinach seeds with deionized water according to the mass ratio of 1 (1-5), and performing steam sterilization at the temperature of 110-;

s2, adding lactic acid bacteria into the fermentation stock solution, and carrying out sealed fermentation for 12-60h at the temperature of 25-40 ℃ to obtain fermentation liquor, wherein the mass ratio of the fermentation liquor to the lactic acid bacteria is 1 (0.02-0.05);

s3, after the fermentation is finished, centrifuging the fermentation liquid at 6000-1000rpm for 10-30min at room temperature, collecting the supernatant, and freeze-drying to obtain the lactobacillus fermented spinach seed extract.

The lactobacillus is one or more of Lactobacillus casei, Leuconostoc and Lactobacillus plantarum.

Preferably, the lactic acid bacteria are a mixture of leuconostoc and lactobacillus plantarum, wherein the leuconostoc and the lactobacillus plantarum are mixed according to the mass ratio of (1-3) to (2-5).

The polyphenol oxidase is combined with an inner capsule membrane in the tissues of fruits and vegetables, can catalyze the hydroxylation reaction of free phenolic acid in the fruits and vegetables and the dehydrogenation reaction of hydroxyl phenol to quinone to generate brown pigment or melanin, and is a key enzyme for causing the browning of the vegetables. The phenolic substances can generate stable intermediates after contributing electrons, and can effectively prevent cells from being oxidized at a physiological level, so that enzymatic browning of the tissue cells of the fruits and vegetables is controlled.

The total phenol content of the lactobacillus fermented spinach seed extract is higher than that of the spinach seed which is not fermented, probably because the lactobacillus generates certain enzymes (such as xylanase and protease) in the fermentation process, the ester bonds connecting the hydroxyl groups of the soluble bound phenol in the spinach seed with long-chain alcohols and other substances are broken through enzymolysis, and the soluble bound phenol is released, so the total phenol content is increased after the fermentation, thereby effectively inhibiting the vegetable histiocyte from browning, playing a certain role in color protection, and simultaneously reducing the loss of nutrient substances.

The film forming agent is one or a mixture of more than two of chitosan, modified chitosan, pullulan polysaccharide and Ag @ CNTs-COOH @ chitosan composite material.

Preferably, the film forming agent is Ag @ CNTs-COOH @ chitosan composite material.

The preparation method of the Ag @ CNTs-COOH @ chitosan composite material comprises the following steps:

s1, adding 1 part by weight of carbon nanotube CNTs into 80-120 parts by weight of 10mol/L aqueous solution of sulfuric acid and 10mol/L aqueous solution of nitric acid in a mass ratio of 1:1, carrying out ultrasonic treatment for 30-60min by using an ultrasonic cell crusher to obtain a mixture, wherein the ultrasonic frequency is 20KHz, the ultrasonic power is 400-500W, then stirring and condensing and refluxing the mixture at 100 ℃ and a rotation speed of 12000rpm for 4-8h, after the reaction is finished, centrifuging at a rotation speed of 8000rpm for 8-15min, washing with deionized water for 4-8 times, putting into a vacuum drying box, and drying at 50-80 ℃ for 6-24h to obtain CNTs-COOH;

s2, adding all CNTs-COOH obtained in S1 and 1-5 parts by weight of silver nitrate into 20-50 parts by weight of deionized water, stirring at the rotating speed of 300-10000 rpm for 20-40min, then adding 2-6 parts by weight of sodium borohydride, continuing stirring for reaction for 5-10h, centrifuging at the rotating speed of 6000-10000rpm for 8-12min after the reaction is finished, washing with deionized water for 2-5 times, and freeze-drying to obtain Ag @ CNTs-COOH;

s3, adding all Ag @ CNTs-COOH obtained in the S2 into 20-50 parts by weight of deionized water to obtain a dispersion liquid A; adding 1 part by weight of chitosan into 20-50 parts by weight of 0.1mol/L acetic acid aqueous solution to obtain solution B; and then mixing the dispersion liquid A and the solution B, carrying out ultrasonic reaction for 40-80min, centrifuging the product at the rotation speed of 4000-8000rpm for 5-15min, washing the product for 4-8 times by using deionized water, and carrying out freeze drying to obtain the Ag @ CNTs-COOH @ chitosan composite material.

The chitosan is a natural polysaccharide, is non-toxic, green and economical, has good stability, film forming property and biocompatibility, has higher protein adsorption capacity, and is a very good substrate material for fixing enzyme. The chitosan is used as a matrix, the modified carbon nano tube is used as an activity enhancing phase, and the modified carbon nano tube contains a large amount of carboxyl negative ions, so that the modified carbon nano tube can be tightly combined with amino positive ions on the chitosan through van der Waals force and electrostatic action on one hand, and can also have amidation reaction on the other hand, thereby realizing uniform doping to form a complex network structure.

Further, silver nanoparticles are widely used as bacteriostatic agents for inorganic materials because of their strong antibacterial properties, but they have disadvantages such as easy agglomeration. The inventor finds that the silver nanoparticle composite material is prepared by loading the silver nanoparticles on the modified carbon nanotube through intermolecular force and adsorption and then combining the modified carbon nanotube with the chitosan matrix, the process conditions are easy to operate, the cost is low, and the dispersibility and the biocompatibility of the silver nanoparticle composite material are improved in the modification process.

The invention not only can effectively block the air holes and skin holes on the surface of the vegetable, inhibit the respiration of the vegetable and reduce the water evaporation, but also has certain inhibiting effect on the microorganisms on the surface of the vegetable, prevents the cross section of the vegetable from browning to a certain extent, plays a role in color protection and effectively prolongs the shelf life of the vegetable by superposing the characteristics of a biobased material on the characteristics of an organic-inorganic composite material, and has low cost and good film forming property.

The emulsifier is one or a mixture of more than two of Tween 20, sodium dodecyl benzene sulfonate and lauroyl arginine ethyl ester hydrochloride.

Preferably, the emulsifier is lauroyl arginine ethyl ester hydrochloride.

The vegetable is any one of leaf vegetables, rhizome vegetables, cauliflower, fresh beans, melons and solanaceous fruits.

The invention has the advantages that:

1. vacuum precooling is adopted, so that the picked vegetables quickly cross the optimal temperature section of various enzymatic and physiological deterioration reactions, and the freshness of the vegetables is ensured to the maximum extent; secondly, the pretreatment liquid calcium chloride is sprayed before vacuum precooling, so that the reduction of the content of protopectin in the vegetables can be inhibited, the softening of the texture of the vegetables is delayed, and the color and the taste are kept.

2. In the step (4), ozone water is used as a cleaning agent in the cleaning process, so that the safety of vegetables in microbiology can be guaranteed, the metabolism of the vegetables can be delayed, the activity of enzymes of the vegetables and the growth of microorganisms of the vegetables are inhibited, and the loss of nutrient substances can be reduced; in addition, the ultrasonic cleaning mode is adopted, so that the contact area of the vegetables and the cleaning liquid can be increased, and the quality of the cleaned vegetables is ensured.

3. The preservative solution in the step (6) has the advantages of simple preparation process, low cost and no toxic or side effect, can effectively inhibit the microbial propagation on the surface of the vegetable, prevents the surface of the vegetable from browning, has good film forming property, can reduce the loss of water and nutrient substances, and prolongs the shelf life of the clean vegetable.

4. And (4) packaging in the step (7) by adopting modified atmosphere packaging filled with high-concentration inert gas, so that cell respiration can be effectively inhibited, vegetable aging can be delayed, and rotting can be inhibited.

The invention provides a clean vegetable processing method which mainly comprises the working procedures of harvesting, vacuum precooling, trimming, cleaning, cutting, fresh keeping, dehydrating, packaging, refrigerating and storing and the like, is safe and efficient, can effectively remove microorganisms on the surface of the clean vegetable, better prolongs the shelf life of the clean vegetable, and furthest ensures the quality and the nutritive value of the clean vegetable.

Detailed Description

The above summary of the present invention is described in further detail below with reference to specific embodiments, but it should not be understood that the scope of the above subject matter of the present invention is limited to the following examples.

Introduction of some raw materials in this application:

the ozone water solution is prepared by an ozone generator and purchased from Jinhao constant environmental protection science and technology Limited in Jinanhao, model CYFS-026;

the method for measuring the concentration of the ozone aqueous solution comprises the following steps: sucking 200mL of ozone water sample, adding the ozone water sample into a 500mL conical flask with a plug, containing 20mL of 20 wt% potassium iodide solution, adding 5mL of 3mol/L sulfuric acid solution, plugging the bottle mouth, uniformly mixing, standing for 5min, titrating with 0.005mol/L sodium thiosulfate standard solution until the solution is light yellow, adding 1mL of 0.5 wt% starch indicator, continuing to titrate until blue just disappears, and recording the total amount of consumed sodium thiosulfate standard solution. The ozone water concentration calculation formula is as follows:

wherein, the concentration of N-ozone water (mg/L); the molar concentration (mol/L) of the standard solution of M-sodium thiosulfate; v-number of milliliters (mL) of sodium thiosulfate standard solution consumed for titration; sampling amount (mL) of W-ozone water.

Vitamin C, CAS No.: 50-81-7 available from Yu food additives Co., Kai, Zhengzhou.

Lauroyl arginine ethyl ester hydrochloride, CAS No.: 60372-77-2, available from Hubei Yuanmeng Biotech, Inc.

Carbon nanotube, type: ENN-CMa11, available from Xinao graphene technology, Inc.

Chitosan, CAS No.: 9012-76-4, molecular weight: 30000, cargo number: c850346, available from McClin Biotechnology, Inc., Shanghai.

Spinach seeds are available from Changchang Dai Co, Jiangsu Lu.

Leuconostoc, latin name: leuconostoc mesenteroides, numbering: GIM1.774, purchased from Guangdong province culture Collection of microorganisms.

Lactobacillus plantarum, latin name: lactobacillus plantarum subsp. GIM1.380, purchased from the Collection of microorganisms of Guangdong province.

The total phenol content of the lactobacillus fermented spinach seed extract and the spinach seed extract is measured by a Folin-Ciocalteu method. Weighing 200mg of the extract, adding 0.5mL of forskolin phenol and 2.3mL of pure water, standing for 1min, adding 2mL of 7.5% (w/v) sodium carbonate solution, mixing at room temperature, performing dark reaction for 2h, and measuring the absorbance value of the reaction solution at 760 nm. The total phenol content was expressed as Gallic Acid Equivalent (GAE) using 60% ethanol-water instead of the sample as a blank. The result shows that the total phenol content in the spinach seeds is improved from 4.87 +/-0.10 mg GAE/g before fermentation to 5.61 +/-0.02 mg GAE/g through lactobacillus fermentation, the P is obviously increased on the level of less than 0.01, and the amplification is 15.81 percent.

Example 1

A clean vegetable processing method is characterized by comprising the following steps:

(1) harvesting, namely harvesting vegetables meeting the harvesting quality requirement in time, and strictly controlling the quality of the vegetables;

(2) vacuum pre-cooling, spraying pretreatment liquid on the surface of the harvested vegetables, then placing the vegetables in a vacuum chamber, starting a vacuum pump and a refrigerating device, turning off the vacuum pump and the refrigerating device when the temperature in the vacuum chamber is reduced to 3 ℃, and keeping for 40min to obtain pre-cooled vegetables; the pretreatment liquid is a 2 wt% calcium chloride aqueous solution, and the spraying amount of the pretreatment liquid is 5% of the mass of the harvested vegetables;

(3) trimming, trimming the pre-cooled vegetables, removing yellow leaves, disease spots and vegetables with unqualified shapes, and making the edible part reach more than 90% to obtain trimmed vegetables;

(4) cleaning, namely putting the trimmed vegetables into 1mg/L ozone water solution circularly flowing at 5 ℃, and simultaneously performing ultrasonic cleaning for 10min under the conditions of 30KHz ultrasonic frequency and 350W ultrasonic power to obtain cleaned vegetables, wherein the bath ratio of the trimmed vegetables to the ozone water solution is 1g: 8 mL;

(5) cutting, namely cutting the cleaned vegetables into 3cm sections, and spraying 100mg/L vitamin C aqueous solution at the flow rate of 10L/min for 60s to obtain the cut vegetables;

(6) and (2) fresh-keeping, namely putting the cut vegetables into a water tank, immersing the cut vegetables in a circulating fresh-keeping solution at the temperature of 3 ℃ for 10min, then taking the cut vegetables out of the water tank under the drive of a conveying net belt, and spraying purified water at the flow of 10L/min for 30s to obtain the fresh-keeping processed vegetables, wherein the bath ratio of the cut vegetables to the fresh-keeping solution is 1g: 5 mL;

(7) dewatering, namely placing the fresh-keeping treated vegetables in a centrifuge for dewatering and drying, wherein the centrifugation conditions are as follows: rotating at 800rpm for 90s to obtain dehydrated vegetables;

(8) packaging, namely putting the dehydrated vegetables into a polyethylene packaging bag with the thickness of 0.05mm, filling the prepared mixed gas, and sealing the bag opening to obtain a packaged product, wherein the mixed gas is nitrogen and oxygen, and the volume ratio of the nitrogen to the oxygen is 90: 10 of mixed gas;

(9) and (4) refrigerating and storing, namely quickly placing the packaged product into a refrigerator for storage, wherein the temperature of the refrigerator is 4 ℃, and the humidity is 80%.

The vegetable is lettuce.

The fresh-keeping solution is prepared from the following raw materials in parts by weight: 6 wt% of plant extract, 3 wt% of film forming agent, 1 wt% of emulsifier and 90 wt% of deionized water. The preparation method of the fresh-keeping liquid comprises the following steps: mixing the components, stirring at 25 deg.C and 1000rpm for 5 hr, and performing ultrasonic treatment for 30min to obtain fresh-keeping liquid, wherein the ultrasonic frequency is 40KHz and the ultrasonic power is 500W.

The plant extract is a spinach seed extract.

The preparation method of the spinach seed extract comprises the following steps: pulverizing fructus Spinaciae, sieving with 60 mesh sieve, extracting with 70 wt% ethanol at a ratio of 1g to 20mL at 70 deg.C under 40KHz ultrasonic frequency and 400W ultrasonic power for 40min, filtering, collecting filtrate, and freeze drying to obtain fructus Spinaciae extract.

The film forming agent is chitosan.

The emulsifier is lauroyl arginine ethyl ester hydrochloride.

Example 2

Essentially the same as in example 1, except that:

the fresh-keeping solution is prepared from the following raw materials in parts by weight: 6 wt% of plant extract, 3 wt% of film forming agent, 1 wt% of emulsifier and 90 wt% of deionized water. The preparation method of the fresh-keeping liquid comprises the following steps: mixing the components, stirring at 25 deg.C and 1000rpm for 5 hr, and performing ultrasonic treatment for 30min to obtain fresh-keeping liquid, wherein the ultrasonic frequency is 40KHz and the ultrasonic power is 500W.

The plant extract is a spinach seed extract.

The preparation method of the spinach seed extract comprises the following steps: pulverizing fructus Spinaciae, sieving with 60 mesh sieve, extracting with 70 wt% ethanol at a ratio of 1g to 20mL at 70 deg.C under 40KHz ultrasonic frequency and 400W ultrasonic power for 40min, filtering, collecting filtrate, and freeze drying to obtain fructus Spinaciae extract.

The film forming agent is a CNTs-COOH @ chitosan composite material.

The preparation method of the CNTs-COOH @ chitosan composite material comprises the following steps:

s1, adding 1 part by weight of carbon nanotube CNTs into 100 parts by weight of aqueous solution mixed by 10mol/L sulfuric acid aqueous solution and 10mol/L nitric acid aqueous solution according to a mass ratio of 1:1, carrying out ultrasonic treatment for 40min by using an ultrasonic cell crusher to obtain a mixture, wherein the ultrasonic frequency is 20KHz, the ultrasonic power is 450W, then stirring and condensing and refluxing the mixture at 100 ℃ and the rotating speed of 1000rpm for 6h, after the reaction is finished, centrifuging at the rotating speed of 6000rpm for 10min, washing with deionized water for 5 times, putting into a vacuum drying oven, and drying at 60 ℃ for 12h to obtain CNTs-COOH;

s2, adding all the CNTs-COOH obtained in the step S1 into 30 parts by weight of deionized water to obtain a dispersion liquid A; adding 1 part by weight of chitosan into 20 parts by weight of 0.1mol/L acetic acid aqueous solution to obtain a solution B; and then mixing the dispersion liquid A and the solution B, carrying out ultrasonic reaction for 60min, centrifuging the product at the rotating speed of 6000rpm for 10min, washing the product for 5 times by using deionized water, and carrying out freeze drying to obtain the CNTs-COOH @ chitosan composite material.

The emulsifier is lauroyl arginine ethyl ester hydrochloride.

Example 3

Essentially the same as in example 1, except that:

the fresh-keeping solution is prepared from the following raw materials in parts by weight: 6 wt% of plant extract, 3 wt% of film forming agent, 1 wt% of emulsifier and 90 wt% of deionized water. The preparation method of the fresh-keeping liquid comprises the following steps: mixing the components, stirring at 25 deg.C and 1000rpm for 5 hr, and performing ultrasonic treatment for 30min to obtain fresh-keeping liquid, wherein the ultrasonic frequency is 40KHz and the ultrasonic power is 500W.

The plant extract is a spinach seed extract.

The preparation method of the spinach seed extract comprises the following steps: pulverizing fructus Spinaciae, sieving with 60 mesh sieve, extracting with 70 wt% ethanol at a ratio of 1g to 20mL at 70 deg.C under 40KHz ultrasonic frequency and 400W ultrasonic power for 40min, filtering, collecting filtrate, and freeze drying to obtain fructus Spinaciae extract.

The film forming agent is Ag @ chitosan composite material.

The preparation method of the Ag @ chitosan composite material comprises the following steps:

adding 2 parts by weight of silver nitrate into 30 parts by weight of deionized water to obtain a solution A; adding 1 part by weight of chitosan into 20 parts by weight of 0.1mol/L acetic acid aqueous solution to obtain a solution B; and then mixing the solution A and the solution B, carrying out ultrasonic reaction for 60min, centrifuging the product at the rotating speed of 6000rpm for 10min, washing the product for 5 times by using deionized water, and carrying out freeze drying to obtain the Ag @ chitosan composite material.

The emulsifier is lauroyl arginine ethyl ester hydrochloride.

Example 4

Essentially the same as in example 1, except that:

the fresh-keeping solution is prepared from the following raw materials in parts by weight: 6 wt% of plant extract, 3 wt% of film forming agent, 1 wt% of emulsifier and 90 wt% of deionized water. The preparation method of the fresh-keeping liquid comprises the following steps: mixing the components, stirring at 25 deg.C and 1000rpm for 5 hr, and performing ultrasonic treatment for 30min to obtain fresh-keeping liquid, wherein the ultrasonic frequency is 40KHz and the ultrasonic power is 500W.

The plant extract is a spinach seed extract.

The preparation method of the spinach seed extract comprises the following steps: pulverizing fructus Spinaciae, sieving with 60 mesh sieve, extracting with 70 wt% ethanol at a ratio of 1g to 20mL at 70 deg.C under 40KHz ultrasonic frequency and 400W ultrasonic power for 40min, filtering, collecting filtrate, and freeze drying to obtain fructus Spinaciae extract.

The film forming agent is Ag @ CNTs-COOH @ chitosan composite material.

The preparation method of the Ag @ CNTs-COOH @ chitosan composite material comprises the following steps:

s1, adding 1 part by weight of carbon nanotube CNTs into 100 parts by weight of aqueous solution mixed by 10mol/L sulfuric acid aqueous solution and 10mol/L nitric acid aqueous solution according to a mass ratio of 1:1, carrying out ultrasonic treatment for 40min by using an ultrasonic cell crusher to obtain a mixture, wherein the ultrasonic frequency is 20KHz, the ultrasonic power is 450W, then stirring and condensing and refluxing the mixture at 100 ℃ and the rotating speed of 1000rpm for 6h, after the reaction is finished, centrifuging at the rotating speed of 6000rpm for 10min, washing with deionized water for 5 times, putting into a vacuum drying oven, and drying at 60 ℃ for 12h to obtain CNTs-COOH;

s2, adding the CNTs-COOH obtained in the S1 and 2 parts by weight of silver nitrate into 30 parts by weight of deionized water, stirring at the rotating speed of 500rpm for 30min, then adding 3 parts by weight of sodium borohydride, continuing stirring for reaction for 6h, centrifuging at the rotating speed of 8000rpm for 10min after the reaction is finished, washing for 3 times by using the deionized water, and freeze-drying to obtain Ag @ CNTs-COOH;

s3, adding the Ag @ CNTs-COOH obtained in the S2 into 30 parts by weight of deionized water to obtain a dispersion liquid A; adding 1 part by weight of chitosan into 20 parts by weight of 0.1mol/L acetic acid aqueous solution to obtain a solution B; and then mixing the dispersion liquid A and the solution B, carrying out ultrasonic reaction for 60min, centrifuging the product at the rotating speed of 6000rpm for 10min, washing the product for 5 times by using deionized water, and carrying out freeze drying to obtain the Ag @ CNTs-COOH @ chitosan composite material.

The emulsifier is lauroyl arginine ethyl ester hydrochloride.

Example 5

Essentially the same as example 4, except that:

the fresh-keeping solution is prepared from the following raw materials in parts by weight: 6 wt% of plant extract, 3 wt% of film forming agent, 1 wt% of emulsifier and 90 wt% of deionized water. The preparation method of the fresh-keeping liquid comprises the following steps: mixing the components, stirring at 25 deg.C and 1000rpm for 5 hr, and performing ultrasonic treatment for 30min to obtain fresh-keeping liquid, wherein the ultrasonic frequency is 40KHz and the ultrasonic power is 500W.

The plant extract is lactobacillus fermented spinach seed extract.

The preparation method of the lactobacillus fermented spinach seed extract comprises the following steps:

s1, crushing the spinach seeds, sieving the crushed spinach seeds with a 80-mesh sieve, mixing the sieved spinach seeds with deionized water according to the mass ratio of 1:3, and performing steam sterilization at the temperature of 125 ℃ for 35min to obtain a fermentation stock solution;

s2, adding lactic acid bacteria into the fermentation stock solution, and carrying out sealed fermentation for 48 hours at the temperature of 30 ℃ to obtain fermentation liquor, wherein the mass ratio of the fermentation liquor to the lactic acid bacteria is 1: 0.04;

s3, after the fermentation is finished, centrifuging the fermentation liquid at 8000rpm for 15min at room temperature, collecting the supernatant, and freeze-drying to obtain the lactobacillus fermented spinach seed extract.

The lactobacillus is Leuconostoc.

The film forming agent is Ag @ CNTs-COOH @ chitosan composite material.

The preparation method of the Ag @ CNTs-COOH @ chitosan composite material comprises the following steps:

s1, adding 1 part by weight of carbon nanotube CNTs into 100 parts by weight of aqueous solution mixed by 10mol/L sulfuric acid aqueous solution and 10mol/L nitric acid aqueous solution according to a mass ratio of 1:1, carrying out ultrasonic treatment for 40min by using an ultrasonic cell crusher to obtain a mixture, wherein the ultrasonic frequency is 20KHz, the ultrasonic power is 450W, then stirring and condensing and refluxing the mixture at 100 ℃ and the rotating speed of 1000rpm for 6h, after the reaction is finished, centrifuging at the rotating speed of 6000rpm for 10min, washing with deionized water for 5 times, putting into a vacuum drying oven, and drying at 60 ℃ for 12h to obtain CNTs-COOH;

s2, adding all CNTs-COOH obtained in S1 and 2 parts by weight of silver nitrate into 30 parts by weight of deionized water, stirring at the rotating speed of 500rpm for 30min, then adding 3 parts by weight of sodium borohydride, continuing stirring for reaction for 6h, centrifuging at the rotating speed of 8000rpm for 10min after the reaction is finished, washing for 3 times by using the deionized water, and freeze-drying to obtain Ag @ CNTs-COOH;

s3, adding all Ag @ CNTs-COOH obtained in the S2 into 30 parts by weight of deionized water to obtain a dispersion liquid A; adding 1 part by weight of chitosan into 20 parts by weight of 0.1mol/L acetic acid aqueous solution to obtain a solution B; and then mixing the dispersion liquid A and the solution B, carrying out ultrasonic reaction for 60min, centrifuging the product at the rotating speed of 6000rpm for 10min, washing the product for 5 times by using deionized water, and carrying out freeze drying to obtain the Ag @ CNTs-COOH @ chitosan composite material.

The emulsifier is lauroyl arginine ethyl ester hydrochloride.

Example 6

Essentially the same as example 4, except that:

the fresh-keeping solution is prepared from the following raw materials in parts by weight: 6 wt% of plant extract, 3 wt% of film forming agent, 1 wt% of emulsifier and 90 wt% of deionized water. The preparation method of the fresh-keeping liquid comprises the following steps: mixing the components, stirring at 25 deg.C and 1000rpm for 5 hr, and performing ultrasonic treatment for 30min to obtain fresh-keeping liquid, wherein the ultrasonic frequency is 40KHz and the ultrasonic power is 500W.

The plant extract is lactobacillus fermented spinach seed extract.

The preparation method of the lactobacillus fermented spinach seed extract comprises the following steps:

s1, crushing the spinach seeds, sieving the crushed spinach seeds with a 80-mesh sieve, mixing the sieved spinach seeds with deionized water according to the mass ratio of 1:3, and performing steam sterilization at the temperature of 125 ℃ for 35min to obtain a fermentation stock solution;

s2, adding lactic acid bacteria into the fermentation stock solution, and carrying out sealed fermentation for 48 hours at the temperature of 30 ℃ to obtain fermentation liquor, wherein the mass ratio of the fermentation liquor to the lactic acid bacteria is 1: 0.04;

s3, after the fermentation is finished, centrifuging the fermentation liquid at 8000rpm for 15min at room temperature, collecting the supernatant, and freeze-drying to obtain the lactobacillus fermented spinach seed extract.

The lactobacillus is lactobacillus plantarum.

The film forming agent is Ag @ CNTs-COOH @ chitosan composite material.

The preparation method of the Ag @ CNTs-COOH @ chitosan composite material comprises the following steps:

s1, adding 1 part by weight of carbon nanotube CNTs into 100 parts by weight of aqueous solution mixed by 10mol/L sulfuric acid aqueous solution and 10mol/L nitric acid aqueous solution according to a mass ratio of 1:1, carrying out ultrasonic treatment for 40min by using an ultrasonic cell crusher to obtain a mixture, wherein the ultrasonic frequency is 20KHz, the ultrasonic power is 450W, then stirring and condensing and refluxing the mixture at 100 ℃ and the rotating speed of 1000rpm for 6h, after the reaction is finished, centrifuging at the rotating speed of 6000rpm for 10min, washing with deionized water for 5 times, putting into a vacuum drying oven, and drying at 60 ℃ for 12h to obtain CNTs-COOH;

s2, adding all CNTs-COOH obtained in S1 and 2 parts by weight of silver nitrate into 30 parts by weight of deionized water, stirring at the rotating speed of 500rpm for 30min, then adding 3 parts by weight of sodium borohydride, continuing stirring for reaction for 6h, centrifuging at the rotating speed of 8000rpm for 10min after the reaction is finished, washing for 3 times by using the deionized water, and freeze-drying to obtain Ag @ CNTs-COOH;

s3, adding all Ag @ CNTs-COOH obtained in the S2 into 30 parts by weight of deionized water to obtain a dispersion liquid A; adding 1 part by weight of chitosan into 20 parts by weight of 0.1mol/L acetic acid aqueous solution to obtain a solution B; and then mixing the dispersion liquid A and the solution B, carrying out ultrasonic reaction for 60min, centrifuging the product at the rotating speed of 6000rpm for 10min, washing the product for 5 times by using deionized water, and carrying out freeze drying to obtain the Ag @ CNTs-COOH @ chitosan composite material.

The emulsifier is lauroyl arginine ethyl ester hydrochloride.

Example 7

Essentially the same as example 4, except that:

the fresh-keeping solution is prepared from the following raw materials in parts by weight: 6 wt% of plant extract, 3 wt% of film forming agent, 1 wt% of emulsifier and 90 wt% of deionized water. The preparation method of the fresh-keeping liquid comprises the following steps: mixing the components, stirring at 25 deg.C and 1000rpm for 5 hr, and performing ultrasonic treatment for 30min to obtain fresh-keeping liquid, wherein the ultrasonic frequency is 40KHz and the ultrasonic power is 500W.

The plant extract is lactobacillus fermented spinach seed extract.

The preparation method of the lactobacillus fermented spinach seed extract comprises the following steps:

s1, crushing the spinach seeds, sieving the crushed spinach seeds with a 80-mesh sieve, mixing the sieved spinach seeds with deionized water according to the mass ratio of 1:3, and performing steam sterilization at the temperature of 125 ℃ for 35min to obtain a fermentation stock solution;

s2, adding lactic acid bacteria into the fermentation stock solution, and carrying out sealed fermentation for 48 hours at the temperature of 30 ℃ to obtain fermentation liquor, wherein the mass ratio of the fermentation liquor to the lactic acid bacteria is 1: 0.04;

s3, after the fermentation is finished, centrifuging the fermentation liquid at 8000rpm for 15min at room temperature, collecting the supernatant, and freeze-drying to obtain the lactobacillus fermented spinach seed extract.

The lactobacillus is a mixture of leuconostoc and lactobacillus plantarum, wherein the leuconostoc and the lactobacillus plantarum are mixed according to the mass ratio of 2: 3.

The film forming agent is Ag @ CNTs-COOH @ chitosan composite material.

The preparation method of the Ag @ CNTs-COOH @ chitosan composite material comprises the following steps:

s1, adding 1 part by weight of carbon nanotube CNTs into 100 parts by weight of aqueous solution mixed by 10mol/L sulfuric acid aqueous solution and 10mol/L nitric acid aqueous solution according to a mass ratio of 1:1, carrying out ultrasonic treatment for 40min by using an ultrasonic cell crusher to obtain a mixture, wherein the ultrasonic frequency is 20KHz, the ultrasonic power is 450W, then stirring and condensing and refluxing the mixture at 100 ℃ and the rotating speed of 1000rpm for 6h, after the reaction is finished, centrifuging at the rotating speed of 6000rpm for 10min, washing with deionized water for 5 times, putting into a vacuum drying oven, and drying at 60 ℃ for 12h to obtain CNTs-COOH;

s2, adding all CNTs-COOH obtained in S1 and 2 parts by weight of silver nitrate into 30 parts by weight of deionized water, stirring at the rotating speed of 500rpm for 30min, then adding 3 parts by weight of sodium borohydride, continuing stirring for reaction for 6h, centrifuging at the rotating speed of 8000rpm for 10min after the reaction is finished, washing for 3 times by using the deionized water, and freeze-drying to obtain Ag @ CNTs-COOH;

s3, adding all Ag @ CNTs-COOH obtained in the S2 into 30 parts by weight of deionized water to obtain a dispersion liquid A; adding 1 part by weight of chitosan into 20 parts by weight of 0.1mol/L acetic acid aqueous solution to obtain a solution B; and then mixing the dispersion liquid A and the solution B, carrying out ultrasonic reaction for 60min, centrifuging the product at the rotating speed of 6000rpm for 10min, washing the product for 5 times by using deionized water, and carrying out freeze drying to obtain the Ag @ CNTs-COOH @ chitosan composite material.

The emulsifier is lauroyl arginine ethyl ester hydrochloride.

Test example 1

Sensory evaluation measurement:

inviting 8 persons with certain vegetable sensory evaluation experience to form an evaluation group, scoring samples of each group of examples according to color, smell, texture and appearance, wherein the total score is 9, the average score is taken as the total sensory score, the sensory score standard is shown in table 1, and the test result is shown in table 2; wherein the storage conditions of the vegetable sample are as follows: the temperature was 4 ℃ and the humidity was 80%.

Table 1: sensory Scoring Standard

Score value	Color	Smell(s)	Texture of	Outer shape
					9	Fresh green	Fragrance	Crisp and tender	Is full
7	Green	Is more fragrant	Is crisp and tender	Is relatively full
					5	Yellowing in leaves	Slightly peculiar smell	The softness and brittleness of the product disappear	So long as it withers
3	The yellowing is more severe	Bad smell is serious	Withering before	The leaves wither and fall
					1	Severe yellowing and scorching	Smelly	Withered and rotten	Severe atrophy

Table 2: sensory Scoring result (score)

Test example 2

And (3) measuring physical and chemical indexes:

and (3) weight loss rate test: by weight of vegetable sample before storage (W)₀) Weight of vegetable sample after storage for a period of time (W)₁) The difference was expressed as a percentage of the weight of the vegetable sample before storage, and the weight loss ratio (%) was [ (W)₁-W₀)/W₀]X is 100%; wherein the storage conditions of the vegetable sample are as follows: the temperature was 4 ℃ and the humidity was 80%.

Measuring the chlorophyll content: weighing 0.5g of vegetable leaves in a mortar, adding a small amount of calcium carbonate powder and 80 wt% of acetone for grinding, homogenizing and filtering, then using 80 wt% of acetone for constant volume to 25mL, and measuring absorbance at the wavelength of 652 nm; chlorophyll content (mg/100g) ═ A₆₅₂X 25X 100)/(34.5X m), wherein A₆₅₂Is the absorbance of chlorophyll at a wavelength of 652nm, and m is the weight (g) of the leaf taken out.

Determination of nitrite content: the test is carried out by using a national standard GB 5009.33-2016 (second method spectrophotometry for measuring nitrite and nitrate in food).

Table 3: vegetable physical and chemical index test result

Comparing example 4 with examples 1-3, it can be seen that the indexes of example 4 are more excellent, probably because the silver nanoparticles and the carbon nanotubes are compounded with the chitosan with good film-forming property in example 4, the characteristics of the organic-inorganic composite material are successfully superimposed with the characteristics of the bio-based material, and the organic-inorganic composite material has low cost and good film-forming property, not only can effectively block pores and skin pores on the surface of the vegetable, inhibit respiration and reduce water evaporation, but also has a certain inhibiting effect on microorganisms on the surface of the vegetable, prevents browning on the section of the vegetable to a certain extent, plays a role in protecting the color, and effectively prolongs the shelf life of the vegetable.

Examples 5-7 compare with example 4, the use of the spinach seed extract fermented by lactic acid bacteria as a plant extract has an effect significantly superior to that of the unfermented spinach seed extract, probably because lactic acid bacteria generate certain enzymes (such as xylanase and protease) during the fermentation process, the ester bond connecting the hydroxyl group of the soluble bound phenol in the spinach seed with long-chain alcohols and other substances is broken by enzymolysis, and the soluble bound phenol is released, so that the total phenol content is increased after the fermentation, thereby effectively inhibiting the vegetable histiocyte from browning, playing a role in protecting the color, and simultaneously reducing the loss of nutrients.

Further comparison of examples 5 to 7 shows that example 7, which uses a mixture of Leuconostoc and Lactobacillus plantarum as a lactic acid bacterium for fermentation of a spinach seed extract, is more effective than the use of Leuconostoc or Lactobacillus plantarum alone.

The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.