CN117730904A - Fresh-keeping packaging and storing method and application special for low-voltage electrostatic field cooperation of new plums - Google Patents
Fresh-keeping packaging and storing method and application special for low-voltage electrostatic field cooperation of new plums Download PDFInfo
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W90/00—Enabling technologies or technologies with a potential or indirect contribution to greenhouse gas [GHG] emissions mitigation
- Y02W90/10—Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics
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- Storage Of Fruits Or Vegetables (AREA)
Abstract
The invention belongs to the technical field of fruit and vegetable fresh-keeping, and discloses a fresh-keeping packaging and storing method special for cooperation of low-voltage electrostatic fields of new plums, which comprises the following steps: the method comprises the following steps of (1) special package non-injury harvesting: selecting new green plum fruits which reach physiological maturity, complete fruit powder and green fruit stalks, putting the new green plum fruits into gloves for non-injury harvesting, and putting the new green plum fruits into a plastic basket with meshes, wherein the inner surface of the plastic basket is provided with special fresh-keeping packages; (2) warehouse entry precooling fumigation; (3) LVEF refrigeration storage. The method integrates a novel plum post-harvest storage and fresh-keeping technical system of 'under-tree non-hurt harvesting, direct loading into special packaging, tying transportation, forklift warehousing, precooling fumigation and under-electric-field storage', the whole process does not involve operations of secondary grading, secondary transportation, secondary basket pouring and the like, mechanical damage is reduced to the greatest extent, the integrity of surface fruit powder is protected, the green and hardness of fruit stalks are kept, the storage period of the novel plums is prolonged to 3 months, the water loss rate is less than 5%, and the good fruit rate is more than 95%.
Description
Technical Field
The invention belongs to the technical field of fruit and vegetable fresh-keeping, and particularly relates to a fresh-keeping packaging and storing method special for cooperation of low-voltage electrostatic fields of new plums and application thereof.
Background
The new plum has aromatic flavor and crisp taste, and is rich in various vitamins, minerals, dietary fibers and antioxidant active ingredients.
The harvesting time of the new plums is concentrated in the high-temperature season of 8-9 months, and the new plums belong to respiratory-leaved fruits, so that physiological metabolism is vigorous after harvesting, and softening and decay begin after about 6 days at normal temperature. The fruit powder of the new plum epidermis is sugar alcohol substances naturally formed in the growth process, on one hand, the water loss after harvest is reduced due to the hydrophobic property of the fruit powder, and on the other hand, the fruit powder has the disease resistance of a natural barrier. The complete fruit powder and the green fruit stem are the signs of the freshness of the new plums. The commercialized links such as harvesting, grading, packaging and the like are extremely easy to produce mechanical injury, so that fruit powder is reduced, fruit stalks turn brown and even black and finally fall off, the evaporation of water and the consumption of substances at the separation layer of pedicel marks are accelerated, and the water loss shrinkage is serious; microorganisms invade from natural tunnels, exacerbating pulp browning and decay.
The existing literature and patent publications relate to a method for storing and preserving fresh plums, which relates to 1-MCP (micro-p-phenyl-carbonate) independent or synergistic bactericide treatment, ice temperature storage, air-conditioning preservation, chemical film coating and the like, the storage period is basically maintained to be 1-2 months unequal, and the method still has a great improvement space from 3 months or more (namely, the price can be doubled before and after the storage to the original denier) of enterprises and market demands.
By searching, the following patent publications related to the present patent application are found:
1. a method for storing prune by ice-temperature air conditioning (CN 114403207A) adopts ice-temperature condition with-5-0deg.C and fluctuation less than or equal to 0.5deg.C in combination with O 2 Concentration of 1-19% CO 2 The prunes are stored and kept fresh under the controlled atmosphere condition with the concentration of 0-5 percent, and the prune storage period is 20-50 days in a mode of warehouse-in step cooling and warehouse-out step heating. However, this method has the following problems: the temperature of the Western Mei Bingdian is about-2.2 ℃, and the ice temperature storage at-5 ℃ possibly causes the Western Mei DonghaiOr cold damage; the prunes are completely after-ripened and enter aging when the prunes are taken out of the warehouse, and the meaning of ripening is not great by charging ethylene gas again; the shelf life did not break through for 2 months.
2. A method for preserving prune and its application (CN 112868750A) includes spraying nutritive antistaling agent before picking, transporting, loading in portable air-regulating box, physiological regulating 1-MCP, and preserving to prevent corrosion. The storage period of the prune is 40 days, and the air-conditioning box for storage has high cost and limited fruit loading (2.0-2.5 kg), and is not suitable for large-scale popularization and application in industry.
3. A method for storing and preserving the pulp of Western Mei Lenglian in logistics and its application (CN 114831173A) includes such steps as picking up methyl jasmonate in the place where pulp is produced, treating with 1-MCP, transporting in cold chain, storing in cold storage at 3-5 deg.C, adding natamycin antistaling paper, and storing in the period of Western Mei Zhucang for 35 days. However, the prune in the patent is contacted with various antistaling agents such as MeJA, 1-MCP, natamycin and the like at the same time, so that the hidden danger of residue exists; the picked links are fumigated firstly, then dried and then put into the portable box to enter the transportation link, the middle part of the link relates to the box pouring operation, and the fruit powder and the fruit stalks are maintained to be very unfavorable.
Based on the current state and the demand of the industry, development of a green physical fresh-keeping technology after new plums are urgently needed, and the storage period is prolonged to 3 months on the premise of ensuring the marketability of fruit colors, flavors, tastes, taste and the like, so that the damage and increment of the new plums are realized.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a fresh-keeping packaging and storage method and application special for cooperation of low-voltage electrostatic fields of new plums.
The technical scheme adopted for solving the technical problems is as follows:
a fresh-keeping packaging and storing method for low-voltage electrostatic field cooperation of new plums comprises the following steps:
(1) And (5) special package non-injury harvesting: selecting new green plum fruits which reach physiological maturity, complete fruit powder and green fruit stalks, putting the new green plum fruits into gloves for non-injury harvesting, and putting the new green plum fruits into a plastic basket with meshes, wherein the inner surface of the plastic basket is provided with special fresh-keeping packages;
the special fresh-keeping package comprises a microporous aluminum foil, a degradable fresh-keeping bag, a shockproof cushion and a special fresh-keeping pad, wherein the microporous aluminum foil is directly wrapped and arranged outside new plum fruits, the degradable fresh-keeping bag is wrapped and arranged outside the microporous aluminum foil, the shockproof cushion is arranged between the bottom of the outer surface of the degradable fresh-keeping bag and the bottom of the plastic basket with meshes, and the special fresh-keeping pad is arranged between the bottom of the outer surface of the microporous aluminum foil and the degradable fresh-keeping bag;
(2) Warehouse entry precooling fumigation: harvesting and packaging new plums, tightly binding the bags, transporting, warehousing in time within 2-12 h, opening the bags after warehousing, synchronously pre-cooling and 1-MCP fumigation in an airtight environment at a warehouse temperature of 0+/-0.5 ℃, wherein the treatment time is 12-14 h, and the 1-MCP concentration is 1-1.5 mu g/m 3 Taking the condition that the temperature of the fruit core is reduced to 0 ℃ as the criterion, and fastening the bag opening after finishing; the timeliness of the 1-MCP fumigation is within 12 hours after fruit picking;
(3) And (5) storing in a LVEF refrigeration house: the new plums after pre-cooling fumigation enter a storage stage, the temperature of the storage warehouse is 0+/-0.5 ℃ and the humidity is 90% -95%, the low-voltage electrostatic field is used for storage, the output voltage of the low-voltage electrostatic field is 2000-4000V, the output current is 3-5 mA, the electrode plate size is 46cm multiplied by 51cm, and the distance between the upper electrode plate and the lower electrode plate is 40cm.
Further, the thickness of the degradable fresh-keeping bag is 0.038+/-0.005 mm, the ventilation aperture is 0.2-0.5 mu m, and the antibacterial rate on escherichia coli and staphylococcus aureus respectively reaches 83% and 92%.
Further, the microporous aluminum foil has a pore density of 200 to 499 pores/cm 2 The pore diameter is 30-50 mu m, and water molecules and 1-MCP can pass through normally.
Further, the special fresh-keeping pad is a composite nanofiber pad with directional water guiding and antibacterial functions, and comprises a water guiding and air permeable layer, a water absorbing and controlled release layer and a waterproof barrier layer, and the specific preparation method comprises the following steps:
(1) Preparation of a water-conducting and breathable layer: firstly, cellulose acetate is dissolved in an acetic acid/water mixed solvent, the mass concentration of the cellulose acetate is 10% -17%, the acetic acid/water mixed solvent is obtained by mixing acetic acid and water, and the acetic acid is as follows: the volume ratio of water is 70: 30-75: 25, magnetically stirring at room temperature until the mixture is fully dissolved; then carrying out electrostatic spinning on the mixed solution, wherein the sample injection rate is 0.5-1 mL/h, the applied voltage is 15-23 kV, the spinning receiving distance is 10-15 cm, and drying the obtained spinning fiber membrane at 60-80 ℃ to obtain the CA water-permeable breathable layer with weak hydrophilicity;
(2) Preparation of a water absorption controlled release layer: firstly, adding polyvinyl alcohol into ultrapure water, wherein the mass concentration of the polyvinyl alcohol is 7% -12%, and heating to 85-100 ℃ to completely dissolve the polyvinyl alcohol to prepare PVA aqueous solution; then sequentially adding acetic acid and chitosan into the PVA water solution, wherein the mass concentration of the acetic acid is 3-12% and the mass concentration of the chitosan is 1-3%, so as to prepare a composite fluid; finally, carrying out electrostatic spinning on the composite fluid, wherein the sample injection rate is 0.05-0.24 mL/h, the applied voltage is 15-23 kV, the spinning receiving distance is 8-12 cm, and the thermal crosslinking temperature is 180-230 ℃, so as to obtain the CS/PVA-AA water absorption and controlled release layer with strong hydrophilicity;
(3) Preparation of a waterproof barrier layer: firstly, dissolving polyurethane in a tetrahydrofuran/N, N-dimethylformamide mixed solvent, wherein the mass concentration of the polyurethane is 12% -17%, and the tetrahydrofuran/N, N-dimethylformamide mixed solvent is obtained by mixing tetrahydrofuran and N, N-dimethylformamide, and the tetrahydrofuran is prepared by mixing: the volume ratio of the N, N-dimethylformamide is 1:1 to 5:1, magnetically stirring at room temperature until the mixture is fully dissolved; then carrying out electrostatic spinning on the mixed solution, wherein the sample injection rate is 0.5-1 mL/h, the applied voltage is 15-23 kV, the spinning receiving distance is 10-15 cm, and drying the obtained spinning fiber membrane at 60-80 ℃ to obtain the PU waterproof barrier layer with hydrophobicity;
(4) Preparation of a special fresh-keeping pad: and (3) sequentially spraying and fixing the prepared water-guiding and air-permeable layer, the water-absorbing and controlled-release layer and the waterproof barrier layer from top to bottom through a glue spraying machine, and compounding to form the CA/CS/PVA-AA/PU special fresh-keeping pad.
Further, the LVEF device is used for storing a low-voltage electrostatic field, the LVEF device comprises a device body, a voltage converter, an upper electrode plate, a lower electrode plate and a plastic basket placing cavity, the upper electrode plate, the lower electrode plate and the plastic basket placing cavity are connected and arranged on the device body, the upper electrode plate and the lower electrode plate are arranged above the lower electrode plate at intervals in parallel, the upper electrode plate and the lower electrode plate are connected with a power supply through the voltage converter, the lower electrode plate is further arranged with the ground, the plastic basket placing cavity is arranged on the device body between the upper electrode plate and the lower electrode plate, and the plastic basket with meshes for containing new plum fruits can be detachably and movably arranged in the plastic basket placing cavity.
The application of the method in fresh-keeping and/or storage of new plums.
The invention has the advantages and positive effects that:
1. aiming at the physiological characteristics of new plum respiratory jump, the innermost layer is made of microporous aluminum foil for packaging fruits, so that the barrier property is strong, and the illumination can be furthest isolated and the moisture can be furthest locked; the degradable fresh-keeping bag on the outer layer further plays roles of preserving moisture and ventilation and regulating the breath of new plum fruits from the natural gas; the special fresh-keeping pad between two layers of packages can guide water vapor generated by fruit respiration or environmental temperature fluctuation into the middle water absorption controlled release layer through the orientation of the weak hydrophilic layer under the capillary force, and can block water locking through the lowest hydrophobic layer. The whole special packaging system is mutually coordinated, so that the integrity of the new plum powder and the freshness of the fruit stalks and fruits are maintained, and the problem of wilting due to water loss after the new plum is picked is solved.
2. The method adopts the external electric field environment created by the LVEF refrigeration house to change the internal inherent electric field of the new plum fruit, inhibit metabolism, regulate physiological enzyme activity, influence respiratory chain electron transfer and the like, and simultaneously generates negative ions which have the effect of decomposing ethylene, and combines 1-MCP fumigation within the accurate aging range after picking to compete ethylene action receptors, thereby jointly delaying the respiratory rate, reducing material consumption and solving the softening aging problem after the new plum is picked.
3. According to the method, the external storage environment influences the cell membrane permeability of microorganisms in a certain range through the two functions of an electric field and ionization of the LVEF refrigeration house, and ions and substances in the membrane act to block physiological and biochemical reactions and the like, so that the microorganisms are killed; the storage environment is filled with chitosan in the special fresh-keeping pad water absorption controlled release layer, and the chitosan has positively charged NH 3+ The groups are typically electrostatically adsorbed by ions to negatively charged components of the microorganism, resulting in leakage of cellular components of the microorganism which causes cell death, along with the leakage of cellular components of the microorganismThe antibacterial interaction between the aluminum foil material and the LVEF forms antibacterial function, so that an antibacterial environment with external prevention and internal control is created together, and the problem of mildew and rot after new plums are picked is solved.
4. The method integrates a novel plum post-harvest storage and fresh-keeping technical system of 'under-tree non-hurt harvesting, direct loading into special packaging, tying transportation, forklift warehousing, precooling fumigation and under-electric-field storage', the whole process does not involve operations of secondary grading, secondary transportation, secondary basket pouring and the like, mechanical damage is reduced to the greatest extent, the integrity of surface fruit powder is protected, the green and hardness of fruit stalks are kept, the storage period of the novel plums is prolonged to 3 months, the water loss rate is less than 5%, and the good fruit rate is more than 95%.
5. Compared with the traditional preservation technology, the low-voltage electrostatic field (Low voltage electrostatic field, LVEF) is used as a non-thermal physical means which is non-contact with fruits, green, harmless, safe and effective, and can form an ion drive environment through space discharge, so that the charge distribution and the water activity in the fruits are influenced within a certain distance range, and the physiological enzyme activity and the growth of microorganisms are further changed. The special package combining the physiological characteristics and fresh-keeping requirements of the new plums needs to be developed, not only has the functions of keeping water and regulating respiration, but also has the functions of slow release and antibiosis.
Drawings
Fig. 1 is a schematic diagram of a package during fresh-keeping treatment of a new plum in the invention;
FIG. 2 is a graph showing the low-voltage electrostatic field treatment of the new plums in the invention; wherein A: a photo diagram of the experimental processed real object; b: the structure connection schematic diagram of the LVEF device;
FIG. 3 is a photograph showing the appearance of the new plum LVEF of the present invention after 90 days of various packaging treatments and storage;
FIG. 4 is a sensory photograph of the present invention after 90 days of storage of the different packaged and electric field treated fresh plums.
Detailed Description
The invention will now be further illustrated by reference to the following examples, which are intended to be illustrative, not limiting, and are not intended to limit the scope of the invention.
The various experimental operations involved in the specific embodiments are conventional in the art, and are not specifically noted herein, and may be implemented by those skilled in the art with reference to various general specifications, technical literature or related specifications, manuals, etc. before the filing date of the present invention.
A fresh-keeping packaging and storing method for low-voltage electrostatic field cooperation of new plums comprises the following steps:
1. and (5) special package non-injury harvesting: selecting new green plum fruits which reach physiological maturity, complete fruit powder and green fruit stalks, putting the new green plum fruits into gloves for non-injury harvesting, and putting the new green plum fruits into a plastic basket 1 with meshes, wherein the inner surface of the plastic basket is provided with special fresh-keeping packages;
as shown in fig. 1, the special fresh-keeping package comprises a microporous aluminum foil 3, a degradable fresh-keeping bag 2, a shockproof buffer pad 6 and a special fresh-keeping pad 5, wherein the microporous aluminum foil is directly wrapped and arranged outside the new plum fruit 4, the degradable fresh-keeping bag is wrapped and arranged outside the microporous aluminum foil, the shockproof buffer pad is arranged between the bottom of the outer surface of the degradable fresh-keeping bag and the bottom of the plastic basket with meshes, and the special fresh-keeping pad is arranged between the bottom of the outer surface of the microporous aluminum foil and the degradable fresh-keeping bag.
The fresh-keeping package is divided into 2 layers, wherein the inner layer is a microporous aluminum foil for directly wrapping new plum fruits, the outer layer is a degradable fresh-keeping bag, a commercially available shockproof buffer pad is padded between the bottom of the outermost plastic basket and the fresh-keeping package, and a special fresh-keeping pad is padded between the microporous aluminum foil and the degradable fresh-keeping bag.
The design and preparation method of the degradable fresh-keeping bag refer to patent ZL202111600215.3 which is issued by the inventor, the thickness of the fresh-keeping bag is 0.038+/-0.005 mm, the ventilation aperture is 0.2-0.5 mu m, and the antibacterial rate on escherichia coli and staphylococcus aureus respectively reaches 83% and 92%.
The pore density of the microporous aluminum foil is 200-499/cm 2 The pore diameter is 30-50 mu m, and water molecules and 1-MCP can pass through normally.
The special fresh-keeping pad is a composite nanofiber pad with directional water guiding and antibacterial functions, and comprises a water guiding and air permeable layer, a water absorbing and controlled releasing layer and a waterproof barrier layer, and the specific preparation method comprises the following steps:
(1) Preparation of a water-conducting and breathable layer: firstly, cellulose Acetate (CA) is dissolved in an acetic acid/water mixed solvent, the mass concentration of the CA is 10% -17%, the acetic acid/water mixed solvent is obtained by mixing acetic acid and water, and the acetic acid is as follows: the volume ratio of water is 70: 30-75: 25, magnetically stirring at room temperature until the mixture is fully dissolved; then carrying out electrostatic spinning on the mixed solution, wherein the sample injection rate is 0.5-1 mL/h, the applied voltage is 15-23 kV, the spinning receiving distance is 10-15 cm, and drying the obtained spinning fiber membrane at 60-80 ℃ to obtain the CA water-permeable breathable layer with weak hydrophilicity;
(2) Preparation of a water absorption controlled release layer: firstly, adding polyvinyl alcohol (PVA) into ultrapure water, wherein the mass concentration of the polyvinyl alcohol is 7% -12%, and heating to 85-100 ℃ to completely dissolve the polyvinyl alcohol to prepare PVA aqueous solution; then adding Acetic Acid (AA) and Chitosan (CS) into the PVA water solution in sequence, wherein the mass concentration of the acetic acid is 3-12% and the mass concentration of the chitosan is 1-3%, so as to prepare a composite fluid; finally, carrying out electrostatic spinning on the composite fluid, wherein the sample injection rate is 0.05-0.24 mL/h, the applied voltage is 15-23 kV, the spinning receiving distance is 8-12 cm, and the thermal crosslinking temperature is 180-230 ℃, so as to obtain the CS/PVA-AA water absorption and controlled release layer with strong hydrophilicity;
(3) Preparation of a waterproof barrier layer: firstly, dissolving Polyurethane (PU) in a Tetrahydrofuran (THF)/N, N-Dimethylformamide (DMF) mixed solvent, wherein the mass concentration of the polyurethane is 12-17%, and the Tetrahydrofuran (THF)/N, N-Dimethylformamide (DMF) mixed solvent is obtained by mixing tetrahydrofuran and N, N-dimethylformamide, and the tetrahydrofuran is: the volume ratio of the N, N-dimethylformamide is 1:1 to 5:1, magnetically stirring at room temperature until the mixture is fully dissolved; then carrying out electrostatic spinning on the mixed solution, wherein the sample injection rate is 0.5-1 mL/h, the applied voltage is 15-23 kV, the spinning receiving distance is 10-15 cm, and drying the obtained spinning fiber membrane at 60-80 ℃ to obtain the PU waterproof barrier layer with hydrophobicity;
(4) Preparation of a special fresh-keeping pad: the prepared water-guiding and air-permeable layer, the water-absorbing and controlled-release layer and the waterproof barrier layer are sequentially fixed by glue spraying through a glue spraying machine, and are compounded to form the CA/CS/PVA-AA/PU special fresh-keeping pad; the special fresh-keeping pad can prevent the fruit powder from being further rotten due to the fact that dew condensation in the new plum package is prevented through directional water guiding, and can prevent the fruit from being withered due to water loss and the fruit stem from being withered and fading due to the fact that the water is locked through the hydrophobic barrier layer, and meanwhile the completeness of the fruit powder and the freshness of the fruit stem are guaranteed.
2. Warehouse entry precooling fumigation: harvesting and packaging new plums, tightly binding the bags, transporting, warehousing in time within 2-12 h, opening the bags (namely opening microporous aluminum foil and degradable fresh-keeping bags) after warehousing, synchronously pre-cooling and 1-MCP fumigation in an airtight environment at a warehouse temperature of 0+/-0.5 ℃, wherein the treatment time is 12-14 h, and the 1-MCP concentration is 1-1.5 mu g/m 3 And (5) taking the condition that the temperature of the fruit core is reduced to 0 ℃ as the standard, and fastening the bag opening after the completion. The timeliness of 1-MCP fumigation is weak in exerting effect within 12 hours after fruit harvest exceeding 24 hours.
3. And (5) storing in a LVEF refrigeration house: the new plums after pre-cooling fumigation enter a storage stage, the temperature of the storage warehouse is 0+/-0.5 ℃ and the humidity is 90% -95%, the plums are stored by using a low-voltage electrostatic field, the output voltage of the low-voltage electrostatic field is 2000-4000V, the output current is 3-5 mA, the size of an electrode plate is 46cm multiplied by 51cm, and the distance between an upper electrode plate and a lower electrode plate is 40cm.
Preferably, a LVEF device as shown in fig. 2 may be used, where the LVEF device includes a device body 11, a voltage converter 7, an upper electrode plate 9, a lower electrode plate 8 and a plastic basket placing cavity 10, where the device body is connected with the upper electrode plate, the lower electrode plate and the plastic basket placing cavity, the upper electrode plate is arranged above the lower electrode plate in parallel with each other at intervals, the upper electrode plate and the lower electrode plate are connected with a power supply (not shown in the figure) through the voltage converter, the lower electrode plate is also grounded, the plastic basket placing cavity is arranged on the device body between the upper electrode plate and the lower electrode plate, and the plastic basket placing cavity can be detachably and movably provided with a plastic basket with meshes for containing new plum fruits, so that the LVEF device is convenient for carrying out low-voltage electrostatic field storage operation on the plastic basket with meshes for containing new plum fruits.
What is not described in detail in the following embodiments is the same as that in this section.
Specifically, the preparation and detection of the correlation are as follows:
example 1
1. Experimental treatment
Fruit powder for reaching physiological maturityThe method comprises the steps of harvesting complete green new plum fruits with fruit stalks in a plant base of new plum seeds in Galilex county in Kaisha of Uygur autonomous region in Xinjiang, putting the new plum fruits into different packages, putting the new plum fruits into a plastic basket with meshes, putting the new plum fruits into a warehouse for precooling within 12 hours, setting the warehouse temperature to be 0+/-0.5 ℃, and synchronously carrying out 1-MCP fumigation treatment in an airtight environment for 12 hours with the concentration of 1 mug/m 3 And after 90 days of storage, counting related indexes.
The different packaging treatments are:
packaging A: an individual net cover; packaging B: an individual aluminum foil; packaging C: net cover and degradable fresh-keeping bag; packaging D: aluminum foil + degradable fresh-keeping bag; packaging E: aluminum foil + degradable fresh-keeping bag + special fresh-keeping pad in the invention.
2. Experimental results
TABLE 1 Effect of different packages on quality of New plums after 90 days of storage
| Index (I) | Packaging A | Packaging B | Packaging C | Packaging D | Package E |
| Loss of water (%) | 7.41 | 5.53 | 5.89 | 5.01 | 4.85 |
| Decay Rate (%) | 32.7 | 12.5 | 13.1 | 7.6 | 6.8 |
| Fruit hardness (kg/cm) 2 ) | / | 5.5 | 5.4 | 8.5 | 10.6 |
As shown in Table 1, the fresh plum fruits packed by the separate net cover are seriously dehydrated and rotted after being stored for 90 days, the dehydration rate and the rotting rate respectively reach 7.41% and 32.7%, and the fruits are completely softened and the hardness is not measurable. The independent aluminum foil and the independent degradable fresh-keeping bag package respectively have the barrier properties of different degrees to water loss and microorganisms, compared with the package A, the moisture loss of fruits is relieved, the hardness of the fruits is kept, meanwhile, the rotting rate is greatly reduced, and the rotting rate is respectively reduced by 20.2 percent and 19.6 percent compared with the package A. The aluminum foil is combined with the degradable fresh-keeping bag to further keep the humidity of the fresh plum storage environment, the water loss rate is close to 5%, the barrier property and disease resistance to microorganisms are further improved, and the decay rate is 7.6%. The package E integrates the special fresh-keeping package, the self-made special fresh-keeping pad is added on the basis of the package D, the water loss rate is only 4.85%, the broad-spectrum antibacterial effect of chitosan is added, the rotting rate is controlled to be 6.8%, and the problems of water loss wilting and mildew and rot of fresh plums after picking are effectively solved. Meanwhile, the aluminum foil, the degradable fresh-keeping bag and the special fresh-keeping pad adopted in the method have a synergistic effect, and the fresh-keeping effect of the new plums can be synergistically promoted.
Example 2
1. Experimental treatment
The new plum fruits which reach the physiological maturity stage, complete fruit powder and greenish fruit stalks are collected in new plum planting bases in Galilex county in the karst area of Uygur autonomous region of Xinjiang, are collected without hurt after being put into 4 different packages, are put into a plastic basket with meshes, are respectively padded with a commercially available shockproof buffer pad and a self-made special fresh-keeping pad at the bottom of the basket, are put into a warehouse for precooling within 12 hours, are subjected to 1-MCP fumigation treatment synchronously in an airtight environment at the warehouse temperature of 0+/-0.5 ℃ for 12 hours, and have the concentration of 1 mug/m 3 After fumigation, the LVEF device is started, the output voltage is 3000V, the output current is 3mA, the electrode plate size is 46cm multiplied by 51cm, and the distance between the upper electrode plate and the lower electrode plate is 40cm. The different packaging processes are shown in fig. 3:
treatment a: single net cover + LVEF; treatment B: aluminum foil + LVEF alone; treatment C: net cover, degradable fresh-keeping bag and LVEF; treatment D: aluminum foil + degradable fresh-keeping bag + LVEF.
2. Experimental results
TABLE 2 Effect of different packages under LVEF on quality of fresh plums after 90 days of storage
| Index (I) | Process A | Process B | Process C | Process D |
| Loss of water (%) | 7.26 | 5.24 | 5.87 | 4.82 |
| Decay Rate (%) | 11.8 | 9.1 | 10.4 | 4.6 |
| Fruit hardness (kg/cm) 2 ) | / | 8.7 | 6.5 | 11.2 |
| Soluble solids content (TSS,%) | 21.2 | 22.4 | 21.5 | 23.4 |
| Total acid content (%) | 0.87 | 1.85 | 1.63 | 2.02 |
As shown in Table 2 and FIG. 3, the sensory and quality changes of different packages stored for 90 days in a low-voltage static field are shown in Table 1 and FIG. 3, the mildew of the new plum fruit packaged by the single net sleeve A is serious, the rotting rate reaches 11.8%, the fruit stalks are all faded and dried and partially fallen off, the joints of the fruit stalks and the fruit shrink, the overall water loss rate reaches 7.26%, the fruit is all softened, and the hardness is not measurable. The fruit stalks are singly packaged by the aluminum foil after being processed B, are changed into yellowish green but not fallen off, the rotting rate is 9.1 percent, the moisture retention is better, the water loss is only 5.24 percent, the fruits are softened to a certain extent, and the TSS and total acid content are kept better; the fruit stalks packaged by the degradable fresh-keeping bags in the treatment C are changed into the yellow brown fruit stalks to fall off, the rotting rate is 10.4 percent, the water loss rate is 5.87 percent, the softening degree of the fruits is greater than that in the treatment B, and compared with the treatment A, the softening and the rotting of the new plum fruits are delayed to a certain degree in the treatment B, and the treatment B has better effect than the treatment C; the treatment D is the special fresh-keeping package for the new plums, the integrity of fruit powder and fruit stalks is effectively maintained by combining electrostatic field treatment, the water loss rate is less than 5%, the good fruit rate is more than 95%, and the TSS and total acid content are maintained at higher levels, so that the fresh-keeping package has a remarkable fresh-keeping effect on the new plums. Meanwhile, the aluminum foil, the degradable fresh-keeping bag and the low-voltage electrostatic field adopted in the method have a synergistic effect, and the fresh-keeping effect of the new plums can be synergistically promoted.
Example 3
1. Experimental treatment: the new plum fruits which reach the physiological maturity stage, complete fruit powder and greenish fruit stalks are picked up at the planting base of new plum seeds in Galilex county in the Kaisha area of Uygur autonomous region in Xinjiang, are picked up without hurt after being put into different packages, are put into a plastic basket with meshes, are put into a warehouse for precooling within 12 hours, the warehouse temperature is set to be 0+/-0.5 ℃, and are subjected to 1-MCP fumigation treatment synchronously in an airtight environment for 12 hours, and the concentration is 1 mug/m 3 The packets were treated with LVEF and stored for 90 days to count the relevant indicators.
The method comprises the following steps: treatment a: an individual net cover; treatment B: the special fresh-keeping package (namely aluminum foil + reducible bag + special fresh-keeping pad); treatment C: single net cover and LVEF treatment; treatment D: special fresh-keeping package and LVEF treatment
2. Experimental results
TABLE 3 Effect of different packagings and electric field treatments on the quality of fresh plums after 90 days of storage
| Index (I) | Process A | Process B | Process C | Process D |
| Loss of water (%) | 7.41 | 4.85 | 7.26 | 4.82 |
| Decay Rate (%) | 32.7 | 6.8 | 11.8 | 4.6 |
| Fruit hardness (kg/cm) 2 ) | / | 10.6 | / | 11.2 |
| Soluble solids content (TSS,%) | 20.8 | 22.5 | 21.2 | 23.4 |
| Total acid content (%) | 0.56 | 1.64 | 0.87 | 2.02 |
As shown in table 3 and fig. 4, the packing results of the new plum separate net cover are expressed in example 1, the water loss and the rot are serious after 90 days of storage, the water loss rate and the rot rate reach 7.41% and 32.7%, respectively, the fruits are all softened, and the hardness is not measurable. In contrast, after LVEF treatment, the antibacterial effect is achieved due to the influence of an electric field and ionization on the permeability of microbial cell membranes and leakage of cell contents, and the decay rate is reduced by 20.9%. The special fresh-keeping package has the effects of moisture preservation, air conditioning, antibiosis and the like, has a new Mei Shishui rate of 4.85 percent and a decay rate of 6.8 percent after 90 days of storage, and simultaneously maintains high levels of TSS and total acid content. Meanwhile, the processing group combining low-voltage electrostatic field and special fresh-keeping package can furthest protect the integrity of surface fruit powder, keep the green and hardness of fruit stalks, delay the respiration aging rate of fruits, create an antibacterial environment with external prevention and internal control, prolong the storage period of new plums to 3 months, and simultaneously, the water loss rate is less than 5%, and the good fruit rate is more than 95%. Meanwhile, the aluminum foil, the degradable fresh-keeping bag, the special fresh-keeping pad and the low-voltage electrostatic field adopted in the method have a synergistic effect, and the fresh-keeping effect of the new plums can be synergistically promoted.
Although embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that: various substitutions, changes and modifications are possible without departing from the spirit and scope of the invention and the appended claims, and therefore the scope of the invention is not limited to the disclosure of the embodiments.
Claims (6)
1. A fresh-keeping packaging and storing method special for cooperation of low-voltage electrostatic fields of new plums is characterized in that: the method comprises the following steps:
(1) And (5) special package non-injury harvesting: selecting new green plum fruits which reach physiological maturity, complete fruit powder and green fruit stalks, putting the new green plum fruits into gloves for non-injury harvesting, and putting the new green plum fruits into a plastic basket with meshes, wherein the inner surface of the plastic basket is provided with special fresh-keeping packages;
the special fresh-keeping package comprises a microporous aluminum foil, a degradable fresh-keeping bag, a shockproof cushion and a special fresh-keeping pad, wherein the microporous aluminum foil is directly wrapped and arranged outside new plum fruits, the degradable fresh-keeping bag is wrapped and arranged outside the microporous aluminum foil, the shockproof cushion is arranged between the bottom of the outer surface of the degradable fresh-keeping bag and the bottom of the plastic basket with meshes, and the special fresh-keeping pad is arranged between the bottom of the outer surface of the microporous aluminum foil and the degradable fresh-keeping bag;
(2) Warehouse entry precooling fumigation: harvesting and packaging new plums, tightly binding the bags, transporting, warehousing in time within 2-12 h, opening the bags after warehousing, synchronously pre-cooling and 1-MCP fumigation in an airtight environment at a warehouse temperature of 0+/-0.5 ℃, wherein the treatment time is 12-14 h, and the 1-MCP concentration is 1-1.5 mu g/m 3 Taking the condition that the temperature of the fruit core is reduced to 0 ℃ as the criterion, and fastening the bag opening after finishing; the timeliness of the 1-MCP fumigation is within 12 hours after fruit picking;
(3) And (5) storing in a LVEF refrigeration house: the new plums after pre-cooling fumigation enter a storage stage, the temperature of the storage warehouse is 0+/-0.5 ℃ and the humidity is 90% -95%, the low-voltage electrostatic field is used for storage, the output voltage of the low-voltage electrostatic field is 2000-4000V, the output current is 3-5 mA, the electrode plate size is 46cm multiplied by 51cm, and the distance between the upper electrode plate and the lower electrode plate is 40cm.
2. The method for fresh-keeping packaging and storing special for cooperation of low-voltage electrostatic fields of new plums according to claim 1, which is characterized by comprising the following steps: the thickness of the degradable fresh-keeping bag is 0.038+/-0.005 mm, the ventilation aperture is 0.2-0.5 mu m, and the antibacterial rate on escherichia coli and staphylococcus aureus respectively reaches 83% and 92%.
3. The method for fresh-keeping packaging and storing special for cooperation of low-voltage electrostatic fields of new plums according to claim 1, which is characterized by comprising the following steps: the pore density of the microporous aluminum foil is 200-499/cm 2 The pore diameter is 30-50 mu m, and water molecules and 1-MCP can pass through normally.
4. The method for fresh-keeping packaging and storing special for cooperation of low-voltage electrostatic fields of new plums according to claim 1, which is characterized by comprising the following steps: the special fresh-keeping pad is a composite nanofiber pad with directional water guiding and antibacterial functions, and comprises a water guiding and air permeable layer, a water absorbing and controlled releasing layer and a waterproof barrier layer, and the specific preparation method comprises the following steps:
(1) Preparation of a water-conducting and breathable layer: firstly, cellulose acetate is dissolved in an acetic acid/water mixed solvent, the mass concentration of the cellulose acetate is 10% -17%, the acetic acid/water mixed solvent is obtained by mixing acetic acid and water, and the acetic acid is as follows: the volume ratio of water is 70: 30-75: 25, magnetically stirring at room temperature until the mixture is fully dissolved; then carrying out electrostatic spinning on the mixed solution, wherein the sample injection rate is 0.5-1 mL/h, the applied voltage is 15-23 kV, the spinning receiving distance is 10-15 cm, and drying the obtained spinning fiber membrane at 60-80 ℃ to obtain the CA water-permeable breathable layer with weak hydrophilicity;
(2) Preparation of a water absorption controlled release layer: firstly, adding polyvinyl alcohol into ultrapure water, wherein the mass concentration of the polyvinyl alcohol is 7% -12%, and heating to 85-100 ℃ to completely dissolve the polyvinyl alcohol to prepare PVA aqueous solution; then sequentially adding acetic acid and chitosan into the PVA water solution, wherein the mass concentration of the acetic acid is 3-12% and the mass concentration of the chitosan is 1-3%, so as to prepare a composite fluid; finally, carrying out electrostatic spinning on the composite fluid, wherein the sample injection rate is 0.05-0.24 mL/h, the applied voltage is 15-23 kV, the spinning receiving distance is 8-12 cm, and the thermal crosslinking temperature is 180-230 ℃, so as to obtain the CS/PVA-AA water absorption and controlled release layer with strong hydrophilicity;
(3) Preparation of a waterproof barrier layer: firstly, dissolving polyurethane in a tetrahydrofuran/N, N-dimethylformamide mixed solvent, wherein the mass concentration of the polyurethane is 12% -17%, and the tetrahydrofuran/N, N-dimethylformamide mixed solvent is obtained by mixing tetrahydrofuran and N, N-dimethylformamide, and the tetrahydrofuran is prepared by mixing: the volume ratio of the N, N-dimethylformamide is 1:1 to 5:1, magnetically stirring at room temperature until the mixture is fully dissolved; then carrying out electrostatic spinning on the mixed solution, wherein the sample injection rate is 0.5-1 mL/h, the applied voltage is 15-23 kV, the spinning receiving distance is 10-15 cm, and drying the obtained spinning fiber membrane at 60-80 ℃ to obtain the PU waterproof barrier layer with hydrophobicity;
(4) Preparation of a special fresh-keeping pad: and (3) sequentially spraying and fixing the prepared water-guiding and air-permeable layer, the water-absorbing and controlled-release layer and the waterproof barrier layer from top to bottom through a glue spraying machine, and compounding to form the CA/CS/PVA-AA/PU special fresh-keeping pad.
5. The method for fresh-keeping packaging and storing special for cooperation of low-voltage electrostatic fields of new plums according to claim 1, which is characterized by comprising the following steps: the LVEF device is used for storing a low-voltage electrostatic field, the LVEF device comprises a device body, a voltage converter, an upper electrode plate, a lower electrode plate and a plastic basket placing cavity, the upper electrode plate, the lower electrode plate and the plastic basket placing cavity are connected to be arranged on the device body, the upper electrode plate and the lower electrode plate are arranged above the lower electrode plate at intervals in parallel, the upper electrode plate and the lower electrode plate are connected with a power supply through the voltage converter, the lower electrode plate is further arranged with the ground, the plastic basket placing cavity is arranged on the device body between the upper electrode plate and the lower electrode plate, and the plastic basket with meshes for containing new plum fruits can be detachably and movably arranged in the plastic basket placing cavity.
6. Use of the method according to any one of claims 1 to 5 for fresh keeping and/or storage of fresh plums.
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