Composite fresh-keeping method of asparagus

Abstract

The invention provides a composite fresh-keeping method for asparagus, which comprises the following steps: pre-cooling a low-pressure fumigation cabin, putting the asparagus into the low-pressure fumigation cabin, then adjusting the pressure to 20KPa, putting a calcium chloride aqueous solution into an atomization kettle, injecting ozone into the atomization kettle, pressurizing to 20KPa to obtain an atomized substance containing ozone-calcium chloride, injecting the atomized substance containing ozone-calcium chloride into the low-pressure fumigation cabin in which the asparagus is placed, and carrying out fresh-keeping treatment on the asparagus. And carrying out low-pressure combined ozone-calcium chloride synergistic fumigation treatment at 10 DEG C and 20 KPa, packaging, and storing, so as to obtain the asparagus subjected to composite preservation. The method can delay chlorophyll degradation of asparagus, delay lignification of tender stems, inhibit spindling of the tender stems and delay the reduction rate of sensory and nutritional quality of the asparagus, is good in effect, can be commercially applied and popularized on a large scale, and has important economic and social values.

Description

Technical Field

[0001] This invention relates to the field of fruit and vegetable storage and preservation technology, and in particular to a method for preserving asparagus. Background Technology

[0002] Asparagus (Asparagus officinalis L.) belongs to the genus Asparagus in the family Liliaceae. It is a perennial root crop, primarily consumed for its tender stems. Asparagus has a crisp and tender texture, a unique flavor, and is rich in amino acids, vitamins, flavonoids, saponins, and other nutrients. Furthermore, asparagus has certain medicinal value, including lowering blood lipids, anti-aging effects, and reducing inflammatory responses, thus earning it the title of "King of Vegetables." As a high-quality vegetable with both premium quality and health benefits, the asparagus industry holds a significant position in my country. Statistics show that my country has become the world's largest producer and exporter of asparagus, and the asparagus industry has become one of the important pillars of my country's distinctive agriculture. However, the cut ends of asparagus roots and the tips of the shoots are susceptible to microbial infection after harvest, and the vigorous physiological metabolism after harvest makes it extremely intolerant to storage, severely limiting its circulation in domestic and international markets. Therefore, developing efficient and safe preservation technologies is of great significance for the positive development of the asparagus industry.

[0003] Calcium ions participate in various physiological reactions in plants, including maintaining membrane structure and function and replenishing intracellular calcium ions to strengthen cell wall structure. Furthermore, as a second messenger in plant cells, calcium ions can bind with calmodulin to form the Ca2+-CaM complex, which can regulate the activity of key enzymes in cellular and plant physiological and biochemical processes, thereby altering metabolic pathways. Studies have found that calcium chloride treatment has a significant impact on postharvest physiological changes and storage tolerance of fruits. Ozone is a powerful oxidant, renowned for its bactericidal capabilities. Unlike other chemicals, ozone decomposes into gas without leaving toxic residues. Ozone can destroy microbial cell membranes and DNA through oxidation, inhibiting microbial growth and reproduction, effectively extending the shelf life of food. Secondly, ozone can also enhance the permeability of microbial cell membranes, blocking the exchange of substances between the inside and outside of cells.

[0004] In recent years, due to the limited preservation effect of single preservation methods, the development of composite preservation technology has gradually become a research hotspot. Composite preservation technology is based on integrating the advantages of single preservatives, thereby achieving a synergistic effect and enhancing the preservation effect. This invention innovatively uses short-time low-pressure treatment technology combined with calcium chloride-ozone fumigation treatment, which can promote the rapid penetration of preservatives, shorten the treatment time, and achieve a good preservation effect.

[0005] I. Physical Preservation Method 1. Low-temperature refrigeration (most commonly used) shortcoming: Chilling injury risk: Asparagus is sensitive to low temperatures; temperatures below [a certain level] will cause it to fall further. It is susceptible to chilling injury, which manifests as sunken buds and water-soaked spots on the stem, followed by rapid rotting after thawing. This limits further reduction in refrigeration temperature.

[0006] Dehydration and wilting: If the humidity of the refrigerated environment is not properly controlled (usually requiring 90-95% high humidity), asparagus will lose water rapidly due to transpiration, resulting in fibrous stems, hardening, and a poor taste.

[0007] Uncurable: Low temperatures can only delay but not completely inhibit the growth of microorganisms and their own physiological metabolism, resulting in a limited shelf life.

[0008] 2. Modified atmosphere packaging / storage shortcoming: The gas ratio is difficult to control: Asparagus has a high respiration rate, and the environment inside the packaging changes rapidly. Too low an O2 level (<2%) will lead to anaerobic respiration and produce an off-flavor; too high a CO2 level (>10%) will cause damage, making the asparagus taste sour and softening its tissues.

[0009] High cost: It requires special packaging materials and precise gas mixing equipment, resulting in high investment and operating costs.

[0010] Risk of secondary damage: If the breathability of the packaging film is not properly selected, it is very easy to accelerate spoilage due to gas imbalance, and the effect may not be as good as ordinary packaging.

[0011] 3. Irradiation preservation shortcoming: Low public acceptance: The term "irradiation" easily arouses panic and resistance among consumers, making market promotion difficult.

[0012] Possible effects on quality: Improper irradiation doses may cause asparagus to soften, change color (turn yellow or fade to green), or develop unpleasant flavors.

[0013] Regulatory and cost constraints: Specialized irradiation facilities are required and subject to strict regulations, resulting in high costs.

[0014] II. Chemical Preservation Method 1. Soaking / spraying with chemical agents (such as chlorine water, chlorine dioxide, sprout inhibitors, etc.) shortcoming: Food safety concerns: This is the biggest drawback. Chemical residues may exceed safe levels, raising consumer health concerns. As people's preference for organic and natural foods increases, market acceptance of this method is declining.

[0015] Limited effect: It can only sterilize the surface and has little effect on inhibiting the physiological aging of asparagus itself (such as fibrosis and lignification).

[0016] Environmental pollution: Used chemical reagents may cause environmental pollution.

[0017] III. Biological Preservation Method (Coating Preservation) shortcoming: The technology is immature: most of it is still in the laboratory research stage, and there are few large-scale commercial applications.

[0018] Cost and process complexity: The extraction and formulation of natural coating materials (such as chitosan and sodium alginate) are costly, and coating processes (such as impregnation and spraying) require additional equipment, making it difficult to rapidly popularize them in the production areas.

[0019] It may affect the appearance and taste: After coating, a thin film may form on the surface of the asparagus, changing its natural luster. If the film is too thick or uneven, it may affect the taste. Summary of the Invention

[0020] The technical problem to be solved by the present invention is to provide a composite preservation method for asparagus in view of the shortcomings of the prior art. This method can delay the degradation of chlorophyll in asparagus, delay the lignification of tender stems, inhibit the excessive growth of tender stems, and slow down the rate of decline in its sensory and nutritional quality. Moreover, the present invention has good effects and can be commercially applied and promoted on a large scale, and has important economic and social value.

[0021] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a compound preservation method for asparagus, the method being as follows: S1. Pre-cool the low-pressure fumigation chamber to 10°C, put asparagus into the low-pressure fumigation chamber, and then adjust the pressure to 20KPa to obtain the low-pressure fumigation chamber with asparagus. S2. Place the calcium chloride aqueous solution in the atomizing vessel, inject ozone into the atomizing vessel, and pressurize to 20 kPa to obtain an atomized substance containing ozone-calcium chloride; S3. The ozone-calcium chloride atomized material obtained in S2 is injected into the low-pressure fumigation chamber containing asparagus obtained in S1. The asparagus is subjected to low-pressure combined ozone-calcium chloride synergistic fumigation treatment under the conditions of 10℃ and 20KPa to obtain fumigated asparagus. S4. After the asparagus obtained from S3 is fumigated, it is packaged and stored to obtain asparagus with composite preservation.

[0022] Preferably, the asparagus in S1 is selected from fresh asparagus that is free from pests and diseases, has no mechanical damage, and has tightly packed scales at the top.

[0023] Preferably, the concentration of the calcium chloride aqueous solution in S2 is 30 mg / L.

[0024] Preferably, the concentration of ozone in S2 is 10 mg / L.

[0025] Preferably, the low-pressure combined ozone-calcium chloride synergistic fumigation treatment in S3 takes 2 hours.

[0026] Preferably, the storage temperature in S4 is 0℃~2℃ and the relative humidity is 85%.

[0027] Preferably, the packaging method described in S4 is as follows: place the asparagus in a 35cm×25cm×20cm food storage box and cover the outside of the food storage box with plastic wrap.

[0028] Preferably, the asparagus after composite preservation in S4 is stored for 46 days.

[0029] Compared with the prior art, the present invention has the following advantages: This invention employs low-pressure (20 kPa) combined with ozone-calcium chloride synergistic fumigation treatment of asparagus. Compared with existing technologies, this invention achieves the following beneficial technical effects: 1. Calcium ions, as important second messengers in plants, participate in regulating various physiological processes. The application of exogenous calcium chloride can reduce the respiration intensity of asparagus during storage, decrease energy and substrate consumption, inhibit ethylene biosynthesis, enhance the integrity and stability of asparagus cell membranes, and reduce leakage of intracellular contents, thereby effectively delaying the senescence process of asparagus, slowing down the rate of quality deterioration, and extending its storage period. Ozone, as a highly effective broad-spectrum bactericide, can rapidly penetrate the cell membranes of pathogenic bacteria, destroying their cell structure and thus inhibiting the rotting of asparagus during storage. Furthermore, ozone can react with ethylene through oxidation, removing ethylene gas from the asparagus storage environment.

[0030] 2. This invention can delay the degradation of chlorophyll in asparagus, delay the lignification of asparagus tender stems, inhibit excessive growth of tender stems, and slow down the rate of decline in its sensory and nutritional quality. Moreover, the method of this invention has a large processing capacity and can be commercially applied, filling the gap in large-scale commercial preservation technology for asparagus.

[0031] 3. The present invention uses low-pressure combined with ozone-calcium chloride synergistic fumigation, which can significantly maintain the quality of asparagus during storage, extend its shelf life and storage period, and the method provided by the present invention can be applied on a large scale and has important economic value.

[0032] The present invention will be further described in detail below with reference to the embodiments. Detailed Implementation

[0033] Example 1 The compound preservation method for asparagus in this embodiment is as follows: S1. Pre-cool the low-pressure fumigation chamber to 10°C, put asparagus into the low-pressure fumigation chamber, and then adjust the pressure to 20 kPa to obtain a low-pressure fumigation chamber for placing asparagus; the asparagus is selected as fresh asparagus that is free from pests and diseases, has no mechanical damage, and has tightly packed scales at the top. S2. Place a calcium chloride aqueous solution with a concentration of 30 mg / L into an atomizing vessel, inject ozone with a concentration of 10 mg / L into the atomizing vessel, and pressurize to 20 kPa to obtain an atomized substance containing ozone-calcium chloride. S3. The ozone-calcium chloride atomized material obtained in S2 is injected into the low-pressure fumigation chamber containing asparagus obtained in S1. Under the conditions of 10℃ and 20KPa, the low-pressure combined ozone-calcium chloride synergistic fumigation treatment is carried out for 2 hours to obtain the fumigated asparagus. S4. The asparagus obtained from the fumigation treatment in S3 is packaged by placing it in a 35cm×25cm×20cm food storage box, covering the outside of the food storage box with plastic wrap, and then storing it under the conditions of 0℃~2℃ and 85% relative humidity to obtain asparagus with composite preservation.

[0034] Comparative Example 1 The asparagus in this comparative example is a blank control, meaning it was not treated in any way.

[0035] Comparative Example 2 The composite preservation method for asparagus in this comparative example is the same as in Example 1, except that the calcium chloride aqueous solution in step S2 is replaced with deionized water.

[0036] Comparative Example 3 The composite preservation method for asparagus in this comparative example is the same as in Example 1, except that ozone is replaced with air in step S2.

[0037] Comparative Example 4 The composite preservation method for asparagus in this comparative example is the same as that in Example 1, except that the pressure in steps S1 to S3 is replaced with atmospheric pressure.

[0038] Comparative Example 5 The composite preservation method for asparagus in this comparative example is the same as that in Example 1, except that the calcium chloride aqueous solution in step S2 is replaced with deionized water and the ozone is replaced with air.

[0039] application: Asparagus was harvested in Lop County, Hotan City, Xinjiang on May 27, 2024. Fresh asparagus with no mechanical damage and tightly packed top scales was selected. After harvesting, it was transported back to the laboratory by refrigerated truck for pre-cooling and packaging. The pre-cooled asparagus was randomly divided into 8 portions, with 30 asparagus in each portion, and treated according to the methods of Example 1 and Comparative Examples 1-5. Quality determination started from the asparagus after S3 fumigation treatment. Samples were taken from each treatment group at 5-day intervals to measure and evaluate relevant indicators of asparagus storage quality, such as total bacterial count, total mold and yeast count, chlorophyll content, and lignin content.

[0040] (1) Total bacterial count determination: Refer to GB 4789.2-2010; (2) Determination of total mold and yeast count: Refer to GB 4789.15-2010; (3) Determination of chlorophyll content: Take 2g of asparagus sample, add calcium carbonate and quartz sand, grind for 5min, then add acetone-water solution and grind again. Wash the ground material repeatedly with a small amount of acetone-water and filter until the asparagus sample is nearly colorless. Transfer the filtrate to a separatory funnel, add 2% sodium sulfate solution, shake for 1min, remove the aqueous layer, and extract with 10mL of ether. Wash and discard the aqueous layer. Transfer the ether layer to a brown bottle containing anhydrous sodium sulfate. Take 20mL of the above solution and dilute to 50mL in a brown volumetric flask. Immediately measure its absorbance at 663 nm and 645 nm (for the acetone system). The calculation formula is as follows: Content calculation: Calculated according to the following Arnon formula: Chlorophyll a (mg / L) = 12.7 × OD 663 - 2.69×OD 645 Chlorophyll b (mg / L) = 22.9 × OD 645 -4.68× OD 663 Total chlorophyll (mg / L) = Chlorophyll a + Chlorophyll b = 20.2 × OD 645 +8.02× OD 663 Determination of lignin content: Fresh asparagus was cut into sections and dried in an oven at 55°C for 8 hours. 0.5 g of the dried sample was added to 100 mL of 95% ethanol and homogenized for 5 minutes. The mixture was then vacuum filtered, and the residue was collected and dried at 5°C for 24 hours. The dried residue was transferred to a test tube, and 0.5 mL of thioglycolic acid solution and 7.5 mL of 2 mol / L hydrochloric acid solution were added. The mixture was boiled for 4 hours, cooled, and centrifuged at 7500 r / min for 15 minutes to obtain the residue. The residue, washed with distilled water, was dissolved in 10 mL of 0.5 mol / L NaOH solution. The reaction mixture was shaken at 25°C for 18 hours and then centrifuged. The supernatant was collected. Transfer the supernatant to a clean test tube, add 2 mL of 2 mol / L hydrochloric acid solution, and precipitate at 4 °C for 4 h. Centrifuge at 7500 r / min for 15 min to obtain the filter residue, which is then dissolved in 10 mL of 0.5 mol / L NaOH solution. Measure the absorbance at 280 nm. Prepare a standard curve using lignin standards of different concentrations, calculate the lignin content in the sample, and express the results in g / kg.

[0041] Storage time determination: The storage period ends when the rate of decay exceeds 30%.

[0042] The measurement results are shown in Tables 1-5.

[0043] Table 1. Initial sterilization rate and colony count results of Example 1 and Comparative Examples 1-5 Note: Lowercase letters in the table indicate the significance of the difference between groups at the P<0.05 level for the same indicator.

[0044] As shown in Table 1, Comparative Example 1 is the control group, and Example 1 is the low-pressure combined ozone-calcium chloride synergistic fumigation treatment group. Through comparative analysis of total bacterial count and initial sterilization rate, the sterilization efficiency of the treatment group Example 1 is much higher than that of the control group Comparative Examples 1-5, and the difference is significant.

[0045] Table 2. Rot rate (%) of asparagus in Example 1 and Comparative Examples 1-5 at different storage times. Note: Lowercase letters in the table indicate the significance of the difference between groups at the P<0.05 level for the same indicator.

[0046] As shown in Table 2, Comparative Example 1 is the control group, and Example 1 is the low-pressure combined ozone-calcium chloride synergistic fumigation treatment group. Through the analysis of the rot rate of asparagus at different storage times, the rot rate of the treatment group Example 1 is much lower than that of the control group Comparative Examples 1 to 5, and the difference is significant.

[0047] Table 3. Chlorophyll content (g / 100g) of asparagus from Examples 1 and Comparative Examples 1-5 at different storage times. Note: Lowercase letters in the table indicate the significance of the difference between groups at the P<0.05 level for the same indicator.

[0048] As shown in Table 3, Comparative Example 1 was the control group, and Example 1 was the low-pressure combined ozone-calcium chloride synergistic fumigation treatment group. Through the analysis of the chlorophyll content of asparagus at different storage times, the chlorophyll content of the treatment group Example 1 was much higher than that of the control group Comparative Examples 1 to 5 in the later stage of storage, and the difference was significant. The low-pressure combined ozone-calcium chloride synergistic fumigation treatment delayed the decrease of chlorophyll content.

[0049] Table 4. Lignin content (g / 100g) of asparagus from Examples 1 and Comparative Examples 1-5 at different storage times. Note: Lowercase letters in the table indicate the significance of the difference between groups at the P<0.05 level for the same indicator.

[0050] As shown in Table 4, Comparative Example 1 was the control group, and Example 1 was the low-pressure combined ozone-calcium chloride synergistic fumigation treatment group. Through the analysis of the lignin content of asparagus at different storage times, the lignin content of the treatment group Example 1 was much lower than that of the control group Comparative Examples 1 to 5 in the later stage of storage, and the difference was significant. The low-pressure combined ozone-calcium chloride synergistic fumigation treatment delayed the increase of lignin.

[0051] Table 5. Storage time results for Example 1 and Comparative Examples 1-5 As shown in Table 5, Comparative Example 1 is the control group, and Example 1 is the low-pressure combined ozone-calcium chloride synergistic fumigation treatment group. Through the analysis of the results of different storage times, the treatment group has the longest storage time. The low-pressure combined ozone-calcium chloride synergistic fumigation treatment delayed the storage time of asparagus.

[0052] The results above show that the storage effect of Example 1 is better than that of Comparative Examples 1 to 5, and the storage effect is even better when the short-time low pressure combined with ozone-calcium chloride atomization fumigation in Example 1 is even better.

[0053] In summary, the preservation method provided by this invention can effectively maintain the quality of asparagus during storage, extend its shelf life, and greatly preserve the commercial value of asparagus. Furthermore, this invention has a large processing capacity and can be applied on a large scale commercially, significantly filling the gap in commercial asparagus preservation technology.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A compound preservation method for asparagus, characterized in that, The method is as follows: S1. Pre-cool the low-pressure fumigation chamber to 10°C, put asparagus into the low-pressure fumigation chamber, and then adjust the pressure to 20KPa to obtain the low-pressure fumigation chamber with asparagus. S2. Place the calcium chloride aqueous solution in the atomizing vessel, inject ozone into the atomizing vessel, and pressurize to 20 kPa to obtain an atomized substance containing ozone-calcium chloride; S3. The ozone-calcium chloride atomized material obtained in S2 is injected into the low-pressure fumigation chamber containing asparagus obtained in S1. The asparagus is subjected to low-pressure combined ozone-calcium chloride synergistic fumigation treatment under the conditions of 10℃ and 20KPa to obtain fumigated asparagus. S4. After the asparagus obtained from S3 is fumigated, it is packaged and stored to obtain asparagus with composite preservation.

2. The composite preservation method for asparagus according to claim 1, characterized in that, The asparagus selected in S1 is fresh asparagus that is free from pests and diseases, has no mechanical damage, and has tightly packed scales at the top.

3. The composite preservation method for asparagus according to claim 1, characterized in that, The concentration of the calcium chloride aqueous solution mentioned in S2 is 30 mg / L.

4. The composite preservation method for asparagus according to claim 1, characterized in that, The ozone concentration mentioned in S2 is 10 mg / L.

5. The composite preservation method for asparagus according to claim 1, characterized in that, The low-pressure combined ozone-calcium chloride synergistic fumigation treatment time described in S3 is 2 hours.

6. The composite preservation method for asparagus according to claim 1, characterized in that, The storage temperature described in S4 is 0℃~2℃ and the relative humidity is 85%.

7. The composite preservation method for asparagus according to claim 1, characterized in that, The packaging method described in S4 is as follows: place the asparagus in a 35cm×25cm×20cm food storage box and cover the outside of the food storage box with plastic wrap.

8. The composite preservation method for asparagus according to claim 1, characterized in that, The asparagus described in S4 has a storage period of 46 days after compound preservation.

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