CN115428826A - A method of electrostatic field combined with solution immersion to realize long-term preservation of air-conditioned fruits and vegetables - Google Patents

Abstract

The invention discloses a method for realizing long-acting preservation of air-conditioned fruits and vegetables by combining electrostatic field and solution soaking, belonging to the technical field of fruit and vegetable preservation. In the invention, the complete fruits and vegetables are soaked in the composite solution and then are put into a modified atmosphere storage with a high-voltage electrostatic treatment device for storage, and in the process, the high-voltage electrostatic field is used for intermittent treatment once in five days to assist in keeping the fruits and vegetables fresh. The composite solution is mixed liquid of 0.05g/L low-concentration kojic acid and Nisin (Nisin), and the soaking time is 5 to 11 minutes; setting the gas proportion to be O in the air-conditioned cold store ₂ :5％～10％、CO ₂ :5％～10％、H ₂ :7％～10％、He:3％～5％、N ₂ 65-80 percent, the direct current high voltage electric field intensity range is 80-120 kV/cm, and the product is stored in the environment of 4 +/-1 ℃. The invention can effectively control the fruits and vegetables to be storedIn the process, the loss of the content of the ascorbic acid, the chlorophyll and the total phenols is avoided, the respiration rate is reduced, most microorganisms are inactivated, the oxidation resistance is improved, the browning degree of the fruits and vegetables is reduced, the hardness and the flavor of the fruits and vegetables are maintained, the original sensory quality and the nutritional value of the fruits and vegetables are maintained to the maximum extent, and the shelf life of the fruits and vegetables can be prolonged by more than 50 days.

Description

A method of electrostatic field combined with solution immersion to realize long-term preservation of air-conditioned fruits and vegetables

technical field

The invention belongs to the technical field of fresh-keeping of fruits and vegetables, and in particular relates to a method for realizing long-term fresh-keeping of fruits and vegetables under air conditioning in combination with an electrostatic field combined with solution immersion.

Background technique

Vegetables have essential mineral nutrients, antioxidant active substances and dietary fiber, so regular consumption can prevent various human diseases such as hyperlipidemia and arteriosclerosis caused by unreasonable dietary structure. Among them, fruits and vegetables are rich in vitamins and sugar. Loved by people. However, some vegetables, such as tomatoes, have strong respiration during storage, and the skin is soft and easy to rot, so they are not resistant to storage; eggplants are prone to browning after mechanical damage, and are prone to mildew during storage. And when the storage conditions are not good, it is easy to cause chilling damage and cause internal tissue to rot. Taking into account people's demand for out-of-season fruits and vegetables and the need for essential nutrients for the crew of long-distance voyages at sea, it is necessary to use efficient and energy-saving fresh-keeping operations to extend the shelf life of fruits and vegetables as much as possible.

The high-voltage electrostatic field is a new fresh-keeping treatment technology that can produce biological effects. It is green and has no residue. It can affect the water structure and protein structure, thereby realizing the regulation of various enzyme activities in fruits and vegetables. Some studies have speculated that the applied electric field will change the potential difference of the biomembrane, thereby generating bioelectric current, inhibiting the generation of ATP, and delaying the metabolism of cells; at the same time, a certain intensity of high-voltage static electricity will generate ozone due to tip discharge, killing microorganisms attached to the surface of fruits and vegetables , and is effective for decomposing volatile substances such as ethylene and ethanol.

The fresh-keeping technology of the controlled atmosphere warehouse is a traditional fresh-keeping method that interferes with the life activities of fruits and vegetables by artificially adjusting the gas composition and temperature of the food storage environment. The controlled atmosphere warehouse has the advantages of advanced facilities, high degree of mechanization, and large storage capacity. On the premise of maintaining the normal physiological metabolism of fruits and vegetables, it can precisely control the temperature, humidity and gas atmosphere of the storage environment, and limit the metabolic rate of fruits and vegetables to the maximum to slow down the aging process. and prevent the growth of microorganisms. Although the modified atmosphere technology has been around for many years, there are still studies that have confirmed that inappropriate gas ratios can cause metabolic disorders of enzymes related to the respiratory chain, reduce the antioxidant activity of fruits and vegetables, cause the accumulation of harmful free radicals, and accelerate aging. The common air-conditioning warehouse adopts the rapid oxygen reduction method to extract the atmosphere and replace it with nitrogen. When the oxygen concentration reaches around 5%, the oxygen is reduced through the respiration of fruits and vegetables and carbon dioxide is produced to achieve the purpose of inhibiting the respiration of fruits and vegetables. However, the controlled atmosphere storage space is large, and improper control of carbon dioxide concentration can easily cause peculiar smell or rot of fruits and vegetables. Therefore, it is difficult to maintain the commercial value of post-harvest vegetables for a long time only by storage in controlled atmosphere storage. Combining with other treatments is an emerging trend to extend the shelf life of fruits and vegetables.

Due to the advantages of low toxicity, safety, and good antibacterial activity, natural preservatives have been widely used in fresh food preservation in recent years and are also accepted by consumers. Nisin is a polypeptide substance produced by Streptococcus lactis, which can cause damage to the vegetative cells of many Gram-positive bacteria, resulting in exudation of intracellular substances and even cell lysis, achieving antibacterial effects. Kojic acid has a wide range of biological activities, is a natural anti-browning agent, and has a strong ability to inhibit the catalytic activity of polyphenol oxidase. Many scholars have studied the anti-browning effect of kojic acid on potato chips, lotus root slices, broccoli, jackfruit and other vegetables and fruits. Studies have shown that various kojic acid preparations can inhibit the browning of the above-mentioned various fruits and vegetables to a certain extent, and can prolong their respectively. Shelf life and color shelf life. Modified atmosphere packaging is often used in combination with 1-methylcyclopropene and other treatments to complement each other's defects in the fresh-keeping process. But at present, there is no report on the preservation of fruits and vegetables by high-voltage electrostatic field treatment combined with immersion in compound solution and assisted controlled atmosphere.

He Jianjun et al. (2020) disclosed "A Method of Modified Atmosphere Packaging Combined with Electrostatic Field Sterilization and Preservation of Fruits and Vegetables" (publication number: CN 111513130A), which uses modified atmosphere packaging for fresh fruits and vegetables that have been pre-cooled in cold storage for 5-18 hours , and then sterilized by a high-voltage pulse electrostatic generator. The sterilization ability, freshness preservation ability and anti-fog performance of this method are all better, but the pulse electric field is often used for liquid sterilization, and its sterilization rate is proportional to the electric field strength. It is not easy to determine the appropriate and moderate electric field strength range. Moreover, this method only reflects the antibacterial aspect, and does not present comprehensive factors such as nutritional components, antioxidant properties, sensory evaluation, etc., and the conclusion on the extension of vegetable shelf life is not completely convincing. This method uses a high-voltage electrostatic field rather than a pulsed electric field for treatment, which can prevent the leaves from wilting due to excessive strength. In addition to sterilization, the high-voltage electrostatic field also has a good control effect on the respiration rate, which can ensure the extension of the shelf life. Adjusted storage instead of modified atmosphere packaging can more accurately control the gas ratio, quickly reduce oxygen to an appropriate concentration to regulate the respiration rate of fruits and vegetables, and the filling of hydrogen and helium can regulate the opening of stomata and prevent the intensification of transpiration.

Wang Yu et al. (publication number: CN 103931757 A) disclosed a method for improving the storage and preservation effect of citrus. The citrus pre-soaked with 5% calcium chloride aqueous solution was placed in parallel metal electrode plates to receive continuous high-voltage electrostatic field treatment. During storage for 60 days, the weight loss rate of citrus decreased greatly, and the activities of peroxidase and pectinase both decreased. However, this method only conducts one-time electric field treatment at the initial stage of the experiment, that is, continuous treatment for 2 to 3 days, each time for 100 to 120 minutes. The electric field has hysteresis and threshold properties, so only one treatment can only maintain the freshness effect of fruits and vegetables for a period of time, and cannot achieve the purpose of long-term freshness preservation. The short-term treatment of calcium chloride aqueous solution has no good effect on sterilization and prevention of browning of fruits and vegetables. This method treats the vegetables with an electric field every five days, and the effect on the enzyme structure and the killing effect on microorganisms are longer; while soaking in the compound solution increases the protection of the color of the fruits and vegetables, and has a better effect on killing corruption. effectiveness of bacteria.

Wu Dan et al. disclosed "a method of pretreatment and coordinated atmosphere for extending the shelf life of fresh-cut oranges" (publication number: CN 111357809 A). Coating, and then storage in controlled atmosphere. The growth of aerobic bacteria and yeast is effectively inhibited, but the loss of ascorbic acid is not low; the respiration rate of fresh-cut fruits and vegetables is often greatly increased due to external damage, but this patent does not show the inhibition of respiration rate, storage time It was only extended by a maximum of 7 days. The method extremely advantageously reduces the respiration rate of the fruits and vegetables, and prolongs the shelf life by at least 40 days.

(publication number: CN 113598225 A) etc. (publication number: CN 113598225 A) disclose the fresh-keeping method of fig. In the method, the figs are sterilized in a certain concentration of ozone for 1 to 2 hours, then precooled for 22 to 24 hours, filled with oxygen, carbon dioxide and nitrogen for gas replacement, and then placed in a high-voltage electrostatic field to keep fresh. The voltage of 1200V ~ 1900V is not so high that ozone cannot be generated by autonomous tip discharge. This method needs to introduce additional ozone for sterilization at the beginning. This method selects the electric field strength range of 80 ~ 120kV/cm, and the thorns are evenly distributed on the upper plate, which can independently decompose and polymerize oxygen into ozone; and the electric field treatment every five days can not only optimize the effect, but also reduce the electric field per day. The cost of operation achieves environmental protection and energy saving under the highest benefit; this method is filled with a small amount of mixed gas of hydrogen and helium in addition to carbon dioxide, oxygen and nitrogen, which can effectively close the pores and have better anti-oxidation and anti-aging effects on fruits and vegetables Effect.

People such as Fang Haitian disclose " a kind of method utilizing low-voltage electrostatic field, low-temperature fresh-keeping jujube " (publication number: CN110915899A), and the long jujube freshly picked is placed in the low-temperature and low-voltage electrostatic field to keep fresh after packing with PE bag, and the field strength is 100~300mV/m. The low-voltage electrostatic field cannot produce ozone independently, so the sterilization effect on fruits and vegetables is not obvious, and the effect on the electron transfer chain is not as good as that of the high-voltage electrostatic field. The method has been determined through pre-experiments that the range of the field strength is 80-120kV/cm, which has a better effect on delaying the oxidation-reduction reaction in the living body.

Cao Liping and others disclosed "A Method of Using Kojic Acid to Preserve Russula" (CN 107646966A). Mixing kojic acid obtained from coconut shell fermentation with leucine can well inhibit the browning and weight loss rate of russula. However, the solution soaking treatment did not affect the respiration rate of fruits and vegetables, and the change of microbial population was not evaluated. The method combines air conditioning, high-voltage electrostatic field treatment and solution immersion, which can effectively regulate the respiration rate of vegetables, reduce transpiration through the influence on stomata, reduce weight loss to a greater extent, maintain texture, and prolong the shelf life of vegetables.

Contents of the invention

The purpose of the present invention is to provide a method for realizing long-term preservation of fruits and vegetables with air conditioning combined with solution immersion in an electrostatic field. The invention reduces the generation of peculiar smell of fruits and vegetables and the softening of meat quality during the storage process by intermittent treatment in electrostatic field and immersion in compound solution combined with controlled atmosphere storage, maintains the surface color of fruits and vegetables, affects the opening of stomata, thereby reducing water loss and transpiration, and maintains The surface is smooth and the meat is firm, reducing color changes and bacterial colony growth, extending the shelf life of vegetables and maintaining nutrients; it can affect the electron transport chain by changing the valence of iron ions, thereby slowing down the metabolic process of fruits and vegetables and improving antioxidant capacity; affecting protein structure and water content The conformation of superimposing the inhibitory effect of enzyme activity; producing ozone, changing the permeability of microbial membrane and prolonging the storage period.

Technical scheme of the present invention:

A method of electrostatic field combined with solution immersion to realize long-term preservation of air-conditioned fruits and vegetables, the steps of which are as follows:

(1) Sorting and cleaning of fruits and vegetables: Sorting fruits and vegetables, selecting fresh fruits and vegetables with uniform size, uniform color, moderate hardness and brittleness, no soft wilting, not soft, not thin, smooth surface, and no mechanical damage; The surface of the sorted fruits and vegetables should be fully pre-cooled with an ice layer, rinsed with sterile water and drained at room temperature;

(2) Preparation of compound solution: mix 0.05g/L kojic acid solution with 0.03% Nisin solution;

(3) Fruit and vegetable soaking: soak the fruit and vegetable treated in step (1) in the compound solution prepared in step (2) and take out and dry;

(4) Controlled atmosphere treatment: Place the fruits and vegetables soaked in step (3) in a controlled atmosphere storage with high-voltage electrostatic field equipment, and fill the storage with preset ratios of O ₂ , CO ₂ , H ₂ , He and N ₂ , the ambient temperature is 4±1°C;

(5) Applying a high-voltage electrostatic field: Place the fruits and vegetables on the shelf under the plate of the high-voltage electrostatic field equipment, lay flat without overlapping, turn on the high-voltage electrostatic field equipment, and the output range is 0-100kV, 0-300μA.

Further, the soaking time of the fruits and vegetables in the compound solution in step (3) is 5-11 minutes.

Further, the initial preset gas volume ratios in the controlled atmosphere storage in step (4) are O ₂ : 5% to 10%, CO ₂ : 5% to 10%, H ₂ : 7% to 10%, He: 3% to 5%, N ₂ : 65% to 80%.

Further, the high-voltage electrostatic field equipment in the step (5) is a magnetoelectric coupling constant temperature device, and an upper pole plate evenly covered with thorns is arranged above the shelf, and the distance between the shelf and the upper pole plate is adjustable, and the maximum movable distance is 10cm; the lower plate is smooth and placed under the shelf; the field strength used ranges from 80 to 120kV/cm, and the single treatment time is 1 to 1.5 hours. The control range is -20℃～25℃.

Further, the frequency of the high-voltage electrostatic field treatment is once every five days, and the treatment lasts for 1 to 1.5 hours.

Further, the fruits and vegetables are conventional fruits and vegetables such as green peppers, tomatoes, and eggplants.

Beneficial effects of the present invention:

(1) Compared with the traditional controlled atmosphere storage of fruits and vegetables, soaking fruits and vegetables in the compound solution of kojic acid and Nisin can have a good bactericidal effect, inhibit the growth of microorganisms, and inhibit the activity of polyphenol oxidase, so that the controlled atmosphere storage The fruits and vegetables with higher growth rate of microbes and browning are slower.

(2) The high-voltage electrostatic field treatment disturbs the metabolism of iron ions, which hinders the electron transfer of the respiratory chain and directly affects the respiration of fruits and vegetables; the addition of energy causes changes in the binding state of water and enzymes, which may lead to the inactivation of some enzymes; the electric field will make Changes in the number of α-helices, β-sheets, etc. change the protein structure and enzyme activity; high-voltage discharge converts oxygen into ozone, which is effective in removing ethylene and ethanol and increasing the permeability of microbial cell membranes, and can kill to a certain extent microorganism. Electric field treatment has threshold value and persistence, and the effect can last for a certain period of time after a single application of electric field. The optimal endurance interval is determined through preliminary tests, that is, it can save electricity and energy while ensuring the effect of inhibiting bacteria and killing enzymes.

(3) When combined with CA, the ozone and negative ions generated by the high-voltage electrostatic field can decompose ethylene, inhibit metabolism, delay the aging of fruits and vegetables, and can oxidize ethanol, formaldehyde, sulfide, benzene series, etc., reducing the pool of CA For the generation of internal odor, the final decomposition products are O ₂ , H ₂ O and CO ₂ , which will not cause secondary pollution. Electric field treatment can generate negative ions, thereby affecting the opening of stomata, alleviating the problem of weightlessness, and slowing down the skin shrinkage of fruits and vegetables.

(4) In this method, the gas charged into the controlled atmosphere storehouse is not only the traditional combination of oxygen, carbon dioxide and nitrogen, but also a mixed gas of hydrogen and helium. Hydrogen, as a mitochondrial antioxidant, can alleviate the lipid peroxidation loss of fruits and vegetables, reduce the decay rate, and increase the activity of antioxidant enzymes; while helium has been proved to be better than carbon dioxide in inhibiting microorganisms, and helium and carbon dioxide may have With synergistic effect, it can kill psychrophilic bacteria and cyclothrix thermophalae, and have a better effect on maintaining the color of the stored goods. This method makes up for the shortcoming that carbon dioxide cannot inhibit the growth of anaerobic bacteria.

(4) The low-temperature synergistic effect of immersion in the compound solution, controlled atmosphere, and electric field not only has high-efficiency sterilization, affects protein structure to change enzyme activity, improves antioxidant capacity, ensures chlorophyll level and cell wall strength, but also avoids the generation of peculiar smell inside the packaging. Inactivate microorganisms. This method makes up for the shortcomings of abnormal respiratory chain reaction and the breeding of microorganisms that are easily formed by single modified atmosphere treatment, and makes up for the problem that single biological reagent soaking treatment cannot ensure the content of nutrients and regulate the respiration rate, and it has no effect on pectinase, chlorophyll degrading enzyme, The inhibitory effect of polyphenol oxidase and other enzyme activities is very significant.

detailed description

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

By comparing the continuous and intermittent treatment of a single electric field, the antibacterial effect was not much different when the frequency was higher than once every 5 days, but the colony growth increased significantly when the treatment interval was more than 5 days, that is, 5 days was the highest interval period of electric field treatment. Frequent or continuous treatment will damage the integrity of the cells, and is not conducive to economic benefits and green energy saving. Therefore, the frequency of electric field treatment is determined to be once every 5 days. See Table 1 for details.

Example 1: High-voltage electrostatic field combined with immersion in compound solution to realize long-term freshness preservation of modified atmosphere green pepper

Control method: (1) Sorting the purchased green peppers, selecting fresh green peppers with uniform size, uniform green color of fruits and vegetables, moderate hardness and brittleness, not soft, not thin, smooth surface, and no mechanical damage; (2) After purchasing (3) Soak the whole green pepper in the compound solution of 0.05g/L kojic acid and 0.03% Nisin for 6 minutes; ( 4) Move the dried green peppers into the controlled atmosphere storage, and place them horizontally under the electrode plates without overlapping each other; (5) Fill hydrogen and helium into the controlled atmosphere storage after nitrogen and oxygen reduction; (6) Every five days , green peppers were treated by high-voltage electric field for 1 hour and 20 minutes. Keep dark and dark during the treatment process, the environment is temperature 4±1°C, relative humidity 90±4%RH; (7) Measure the index storage every five days. The results show that the gas ratio of 5%O ₂ +5%CO ₂ +7%H ₂ +4%He+79%N ₂ combined with 100kV/cm electric field treatment synergistically pre-soaked in the compound solution, compared with the control group, significantly improved Chlorophyll retention rate (66.97%) and ascorbic acid retention rate (45.66%) of green pepper; respiration rate decreased by 19.98%, total bacterial colony decreased by 19.02%; weight loss did not exceed 1.5% during storage, hardness increased by 40.60%, and sensory evaluation was not low The activity of superoxide dismutase was improved (19.63%), and the activity of polyphenol oxidase was inhibited (31.68%); the response value of alcohol, aldehyde, and aromatic compound decreased by 36.80%, and the content of nitrate increased but significantly lower than that of the untreated control sample. The shrinkage and dehydration of green peppers are not obvious, the surface is relatively smooth, and there is no unpleasant odor in the controlled atmosphere storage, and the storage period is extended to more than 50 days. See Table 2 and Table 3 for comparison of storage endpoint test indicators of green peppers with different treatments.

Example 2: High-voltage electrostatic field combined with immersion in compound solution to achieve long-term freshness preservation of modified atmosphere tomatoes

Control method: (1) Sorting the purchased tomatoes, selecting fresh tomatoes with uniform size, uniform fruit and vegetable color, moderate hardness, no soft pits, not soft, not thin, smooth surface, and no mechanical damage; (2) Purchasing The finished tomatoes are pre-cooled, transported to the laboratory, washed with sterile water, drained at room temperature, and wiped with kitchen paper; (3) The whole tomato is immersed in the compound solution of 0.05g/L kojic acid and 0.03% Nisin 8 minutes; (4) Move the dried tomatoes into the controlled atmosphere storage, and place them horizontally under the electrode plates without overlapping each other; (5) Fill hydrogen and helium into the controlled atmosphere storage after nitrogen and oxygen reduction; (6) Every five days, the tomatoes were treated with a high-voltage electric field for 1 hour and 30 minutes. Keep dark and dark during the treatment process, the environment is temperature 4±1°C, relative humidity 90±4%RH; (7) Measure the index storage every five days. The results show that the gas ratio of 8%O ₂ +10%CO ₂ +8%H ₂ +5%He+69%N ₂ combined with 120kV/cm electric field treatment and synergistically soaking the compound solution for 8 minutes, compared with the control group, significantly improved The lycopene retention rate (18.27%) and ascorbic acid retention rate (39.45%) of tomato were improved; the respiration rate decreased by 19.50%, and the total number of colonies decreased by 51.12%; The evaluation was not lower than 5 points; the activity of superoxide dismutase was increased (18.41%), and the activity of polyphenol oxidase was inhibited (33.06%); the response value of alcohols, aldehydes, and aromatic compounds decreased by 34.76%, and the content of nitrate decreased by 34.76%. increased but significantly lower than that of untreated control samples. The water loss and shrinkage of the tomato was not obvious, and there was no unpleasant odor inside the controlled atmosphere storage, and the storage period was extended to more than 50 days. See Table 2 and Table 3 for the comparison of the end point test indicators of tomato storage in different treatments.

Example 3: High-voltage electrostatic field combined with compound solution soaking to realize long-term preservation of modified atmosphere eggplant

Control method: (1) sort the purchased green eggplants, and select fresh eggplants with uniform size, uniform color, moderate hardness, not soft, not thin, smooth surface, and no mechanical damage; (2) pre-purchased eggplants cold, transported to the laboratory, washed with sterile water after purchase, drained at room temperature, and wiped with kitchen paper; (3) soak the whole eggplant in the compound solution of 0.05g/L kojic acid and 0.03% Nisin10 (4) The dried tomatoes are moved into the controlled atmosphere storage, and placed horizontally under the electrode plate without overlapping each other; (5) After nitrogen and oxygen reduction, hydrogen and helium are filled into the controlled atmosphere storage to maintain the gas ratio 10% O ₂ , 5% CO ₂ , 10% H ₂ , 4% He, 71% N ₂ ; (6) Every five days, the tomatoes were treated with high voltage electric field for 1 hour and 30 minutes. Keep dark and dark during the treatment process, the environment is temperature 4±1°C, relative humidity 90±4%RH; (7) Measure the index storage every five days. The results showed that the gas ratio of 10%O ₂ +5%CO ₂ +10%H ₂ +4%He+71%N ₂ combined with 85kV/cm electric field treatment synergistic solution soaking for 11 minutes, compared with the control group, significantly improved the The retention rate of polyphenols (33.65%) and ascorbic acid (39.16%); the respiratory rate decreased by 21.18%, the total number of colonies decreased by 51.07%; the weight loss did not exceed 2.0% during the whole storage process, the hardness increased by 36.14%, and the sensory evaluation was not low The activity of superoxide dismutase was improved (25.09%), and the activity of polyphenol oxidase was inhibited (30.57%); the response value of alcohol, aldehyde, and aromatic compound decreased by 38.43%, and the content of nitrate increased but significantly lower than that of the untreated control sample. There was no unpleasant odor in the air-conditioned storage room, and the storage period was extended to more than 50 days. See Table 2 and Table 3 for comparison of storage endpoint test indicators of eggplant with different treatments.

Contrasts 1, 2 and 3 in Table 3 are green peppers, tomatoes and eggplants without any treatment.

(1) Comparison of the antibacterial effect (log CFU/g) between electric field intermittent treatment and continuous treatment

Table 1 Comparison of antibacterial effects of different electric field treatments on whole fruits and vegetables

Green pepper tomato eggplant Test starting point (0 days) 3.25 1.59 3.52 Continuous processing (50 days) 5.76 5.88 6.12 Intermittent treatment once a day (50 days) 5.79 5.91 6.18 Intermittent treatment once every 3 days (50 days) 5.87 5.89 6.49 Intermittent treatment once every 5 days (50 days) 5.82 5.96 6.18 Intermittent treatment once every 7 days (50 days) 6.43 6.14 6.52 Intermittent treatment every 9 days (50 days) 6.75 6.23 6.61

(2) Comparison of test indicators of different embodiments (three kinds of fruits and vegetables) stored for 0 days, see Table 2 for details:

Table 2 Comparison of storage starting point test indicators in different embodiments (three kinds of fruits and vegetables)

(3) The performance test is carried out when the storage time is 50 days, see Table 3 for details:

Table 3 Comparison of storage endpoint test indicators in different embodiments (three kinds of leafy vegetables)

(4) Comparison of high-voltage pulsed electric field (one-time treatment) and high-voltage electrostatic field (once every 5 days) on the quality and bactericidal efficacy of fruits and vegetables (green peppers) stored for 50 days, see Table 4 for details:

Table 4 Comparison of high-voltage pulsed electric field and high-voltage electrostatic field on the quality and bactericidal efficacy of green peppers stored for 50 days

Storage endpoint test indicators High voltage pulsed electric field treatment High voltage electrostatic field treatment MDA(nmol/g) 30.67 24.51 Total number of colonies (logCFU/g) 7.21 7.58 shelf life (d) 26 30

Although the total number of colonies of green peppers after high-voltage pulsed electric field treatment was lower, the difference was not significant compared with high-voltage electrostatic field treatment, and the content of malondialdehyde at the end of the storage period, an index that symbolized the degree of membrane lipid peroxidation, was higher. One-time treatment of fruits and vegetables by high-voltage pulsed electric field will destroy the integrity of the cell membrane, affect the selective permeability of the plasma membrane, and shorten the shelf life.

Invention principle: The high-voltage electrostatic field puncture point discharge makes the ozone component in the modified atmosphere packaging, which effectively kills microorganisms, and decomposes alcohol, aldehyde, benzene series, and aromatic compounds due to its strong oxidation ability, thereby reducing the generation of peculiar smell in the packaging , to make up for the defects that the air conditioning itself is easy to condense water mist to breed microorganisms and produce volatile flavors; pre-soaking in the compound solution can inhibit the growth of bacteria, inhibit the activity of polyphenol oxidase, adjust the opening of stomata and relieve water loss; kojic acid The reagent can effectively reduce the accumulation of plant nitrate content during long-term storage and reduce the risk of cancer; the gas filled in the controlled atmosphere warehouse is added with a mixed gas of hydrogen and helium. Hydrogen, as a mitochondrial antioxidant, can alleviate the lipid peroxidation loss of fruits and vegetables, reduce the decay rate, and increase the activity of antioxidant enzymes; while helium has been proved to be better than carbon dioxide in inhibiting microorganisms, and helium and carbon dioxide may have With synergistic effect, it can kill psychrophilic bacteria and cyclothrix thermophagae, and has a better effect on maintaining the color of the stored goods. This method makes up for the shortcoming that carbon dioxide cannot inhibit the growth of anaerobic bacteria.

Claims (6)

1. A method for realizing long-acting preservation of air-conditioned fruits and vegetables by combining electrostatic field and solution soaking is characterized by mainly comprising the following steps:

(1) Sorting and cleaning fruits and vegetables: sorting fruits and vegetables, and selecting fresh fruits and vegetables with uniform size, uniform color, moderate hardness and brittleness, no soft and wilting, no soft and thin meat, smooth surface and no mechanical damage; fully pre-cooling the ice coating on the surfaces of the sorted fruits and vegetables, cleaning the fruits and vegetables by using sterile water, and draining the fruits and vegetables at room temperature;

(2) Preparation of a compound solution: mixing 0.05g/L kojic acid solution with 0.03% Nisin solution;

(3) Fruit and vegetable soaking: soaking the fruits and vegetables processed in the step (1) in the compound solution prepared in the step (2), taking out and airing;

(4) Modified atmosphere treatment: placing the fruits and vegetables soaked in the step (3) into a modified atmosphere storage with high-voltage electrostatic field equipment, and filling O with a preset proportion into the storage ₂ 、CO ₂ 、H ₂ He and N ₂ The ambient temperature is 4 +/-1 ℃;

(5) Applying a high-voltage electrostatic field: placing fruits and vegetables on a shelf below a polar plate of high-voltage electrostatic field equipment, flatly paving without overlapping, starting the high-voltage electrostatic field equipment, and outputting the fruits and vegetables in a range of 0-100 kV and 0-300 muA;

2. the method for achieving long-acting preservation of controlled atmosphere fruits and vegetables by soaking in combination of an electrostatic field and a solution according to claim 1, wherein the soaking time of the fruits and vegetables in the compound solution in the step (3) is 5-11 minutes.

3. The method of claim 1, wherein the initial predetermined gas volume ratio in the modified atmosphere storage of step (4) is O ₂ :5％～10％、CO ₂ :5％～10％、H ₂ :7％～10％、He:3％～5％、N ₂ :65％～80％。

4. The method for achieving long-acting preservation of modified atmosphere fruits and vegetables by combining electrostatic field and solution soaking according to claim 1, wherein the high-voltage electrostatic field equipment in the step (5) is a magnetoelectric coupling constant temperature device, an upper polar plate uniformly distributed with burs is arranged above a storage rack, the distance between the storage rack and the upper polar plate is adjustable, and the maximum movable distance is 10cm; the lower polar plate is smooth and is arranged below the storage rack; the field intensity range is 80-120 kV/cm, the single treatment time is 1-1.5 hours, and the corresponding time length is adjusted according to different field intensities; the temperature in the device can be regulated and controlled within the range of-20 ℃ to 25 ℃.

5. The method of claim 1, wherein the frequency of the high voltage electrostatic field treatment is once every five days for 1-1.5 hours.

6. The method for realizing long-term fresh keeping of the fruits and vegetables in the controlled atmosphere storage by combining the electrostatic field with the solution soaking according to claim 1, wherein the fruits and vegetables are conventional fruits and vegetables such as green peppers, tomatoes, eggplants and the like.