Preparation method and application of methyl jasmonate composite fresh-keeping liquid

Abstract

The invention discloses a methyl jasmonate composite fresh-keeping liquid preparation method, which comprises: crushing milkvetch root and licorice root, placing the crushed milkvetch root and licorice root, honeysuckle flower, chrysanthemum flower and deionized water in an ultrasonic wave device, adding cellulase, hemicellulase, pectinase and an acid-base regulator, and carrying out ultrasonic extraction, filtration and centrifugation to obtain an extraction liquid; the preparation method comprises the following steps: dissolving methyl jasmonate and lecithin in ethanol, uniformly mixing, and adding deionized water to prepare a methyl jasmonate solution; and mixing the jasmonic acid methyl ester solution and the leaching solution according to a certain volume ratio to obtain the jasmonic acid methyl ester composite fresh-keeping solution. The methyl jasmonate composite fresh-keeping liquid is used for carrying out spraying treatment and low-temperature ventilation treatment on blueberries after the blueberries are picked, so that the reduction of hardness and soluble solids in the storage process of the blueberries can be effectively relieved, the problems that the picked blueberries are easy to soften, rot and deteriorate and the like are solved, the shelf life of the blueberries is prolonged, and the commodity value of the blueberries is improved. The composite fresh-keeping liquid is safe, non-toxic, simple to prepare and easy to popularize.

Description

Technical Field

[0001] The invention relates to the technical field of fruit and vegetable preservation, and in particular to a preparation method of a methyl jasmonate composite fresh-keeping liquid and application thereof. Background Art

[0002] Blueberry belongs to the Ericaceae family and the genus Vaccinium. It is a perennial deciduous or evergreen shrub. It is a small round berry with extremely high nutritional value. The fruit is dark blue-purple and has a high content of organic acids and sugars. The fruit is rich in nutrients such as anthocyanins, anthocyanins, mineral elements, phenolic substances and vitamins, and is known as the "king of berries". Blueberries have the functions of protecting cardiovascular and preventing chronic diseases, and are listed as one of the five major health foods for humans by the Food and Agriculture Organization of the United Nations. Blueberries are generally harvested in the hot and rainy summer. After harvesting, the fruit continues to undergo respiratory metabolism to maintain physiological activities, consume fruit nutrients, lose water quickly, and metabolize cells in the fruit rapidly. Cell wall materials are gradually degraded under the action of hydrolases, making the fruit very easy to soften, rot and deteriorate, reducing the quality of the fruit.

[0003] Low temperature storage is currently one of the most effective ways to extend the shelf life of blueberries. However, after blueberries are transferred from cold storage to room temperature, they are more likely to rot and soften, and the fruit base will also be sunken, affecting the quality and commercial value of blueberries. my country's cold chain system is not yet perfect, and blueberries are often eaten fresh. Low temperature refrigeration affects their taste and is not easy for everyone to eat immediately, especially the elderly and some special groups who are not suitable for eating refrigerated foods.

[0004] Therefore, there is an urgent need to find a storage and preservation method that can maintain the quality of post-harvest blueberries, inhibit their softening, and delay their decay and deterioration, so as to increase the shelf life and commodity value of blueberries. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing a methyl jasmonate composite fresh-keeping liquid and its application, so as to solve the problem that blueberries are easy to soften, rot and deteriorate as mentioned in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for preparing a methyl jasmonate composite fresh-keeping liquid, comprising the following steps:

[0007] Step 1, preparation of extract: weigh 35-40 parts by weight of Astragalus, 30-35 parts by weight of Licorice, 12-15 parts by weight of Honeysuckle, 5-8 parts by weight of Chrysanthemum, and 150-160 parts by weight of deionized water, place them in an ultrasonic device, then add enzyme preparations and acid-base regulators, perform ultrasonic extraction, filter, and centrifuge to obtain an extract.

[0008] Step 2, preparation of methyl jasmonate solution: dissolve methyl jasmonate and lecithin in ethanol, stir and mix them evenly, and then add deionized water to prepare a 45-50 μmol / L methyl jasmonate solution.

[0009] Step 3: Mix the methyl jasmonate solution and the extract in a volume ratio of 1:3 to 3.5 to obtain a methyl jasmonate composite preservative solution.

[0010] The application of methyl jasmonate composite preservative liquid in the preservation of blueberries is processed by the following method and steps:

[0011] S1. The harvested blueberries are sprayed with a methyl jasmonate composite fresh-keeping liquid, wherein the spraying amount of the methyl jasmonate composite fresh-keeping liquid is 2-3% of the mass of the blueberries.

[0012] S2. Place the sprayed blueberries at 16-18°C for 4-5 hours under ventilation, and then package them in polyethylene terephthalate boxes.

[0013] As a preferred technical solution of the present invention, the enzyme preparation is composed of cellulase, hemicellulase and pectinase in a mass ratio of 2:1 to 1.2:1, the amount of enzyme preparation added is 0.3 to 0.5% of the total amount of deionized water, the cellulase activity is 20 to 25 U / mg, the hemicellulase activity is 3 to 5 U / mg, and the pectinase activity is 3 to 5 U / mg.

[0014] As a preferred technical solution of the present invention, before weighing the astragalus and licorice, the method further comprises: crushing the astragalus and licorice to make the particle size of the astragalus and licorice be 0.5-1.0 mm.

[0015] As a preferred technical solution of the present invention, the frequency of the ultrasonic equipment is 110-115 Hz, the temperature is 35-40° C., and the time is 40-45 min.

[0016] As a preferred technical solution of the present invention, the acid-base regulator is any one of citric acid and malic acid or a mixture of the two substances, and the pH value is adjusted to 5.5-6.5.

[0017] As a preferred technical solution of the present invention, the centrifugal speed is 2000-2200 rpm.

[0018] As a preferred technical solution of the present invention, the purity of the methyl jasmonate is 98%, and the mass ratio of methyl jasmonate to lecithin is 3:1.

[0019] As a preferred technical solution of the present invention, the volume concentration of the ethanol is 2-2.5%.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. Flavonoids in the extracts of Astragalus, Licorice, Honeysuckle and Chrysanthemum can effectively inhibit the growth of microorganisms on the surface of fruits and vegetables, remove free radicals generated during storage, protect the integrity of fruit and vegetable cell membranes, and delay the aging and corruption of fruits and vegetables; at the same time, flavonoids can inhibit the respiration of fruits and vegetables, reduce the loss of water in fruits and vegetables, slow down the consumption of sugar content and other nutrients, and maintain the nutritional value of fruits and vegetables. Polysaccharides in Astragalus, such as Astragalus polysaccharide, can form a protective film on the surface of fruits and vegetables, reducing the evaporation of water on the surface of fruits and vegetables; active ingredients in licorice, such as glycyrrhizic acid and glycyrrhizin, have antioxidant and antibacterial effects, and can protect the integrity of fruit and vegetable cell membranes; Honeysuckle contains active ingredients such as luteolin, inositol, and volatile oils, which can bind to the cell membrane of microorganisms, destroy their cell structure or interfere with their metabolic process, and delay the shrinkage process of fruits; Chrysanthemum contains a variety of active ingredients such as chrysanthemum glycosides and polyphenol compounds, which can play an antibacterial and antioxidant role on fruits and vegetables. The composite preservative solution is obtained by mixing methyl jasmonate solution with extracts made from medicinal and edible substances such as astragalus, licorice, honeysuckle and chrysanthemum. The composite preservative solution overcomes the defects of the single methyl jasmonate solution, can effectively reduce the softening of blueberry fruits, delay their decay and deterioration, and improve their commercial value. At the same time, astragalus, licorice, honeysuckle and chrysanthemum are medicinal and edible substances, which are safe and non-toxic.

[0022] 2. The present invention adopts ultrasonic extraction of astragalus, licorice, honeysuckle and chrysanthemum, controls the temperature, frequency and pH value of the ultrasonic solution, and utilizes the cavitation effect, mechanical effect and thermal effect of ultrasound to rupture the cell walls of astragalus, licorice, honeysuckle and chrysanthemum to release effective active ingredients.

[0023] 3. The present invention adds cellulase, hemicellulase and pectinase during the ultrasonic extraction of astragalus, licorice, honeysuckle and chrysanthemum. Cellulase can decompose cellulose in the cell walls of astragalus, licorice, honeysuckle and chrysanthemum, destroy the dense structure of the cell walls, and make flavonoids more easily released from the cells; hemicellulase can hydrolyze hemicellulose connected to flavonoids, which is beneficial to the extraction of flavonoids; pectinase can decompose pectin in the cell walls of astragalus, licorice, honeysuckle and chrysanthemum, further destroy the cell structure, and improve the dissolution rate of flavonoids. The mixture of cellulase, hemicellulase and pectinase can play a synergistic role, better destroy the cell walls of licorice and honeysuckle, improve the dissolution rate of effective ingredients such as glycyrrhizic acid in licorice and the extraction rate of effective ingredients such as inositol in honeysuckle, and thus improve the preservation effect of fruits and vegetables.

[0024] 4. The present invention adds lecithin to the composite fresh-keeping liquid. Lecithin can change the surface tension of the solution, making the fresh-keeping liquid easier to spread after spraying, thereby accelerating the drying speed of the fresh-keeping liquid on the surface of fruits and vegetables; furthermore, lecithin has antioxidant properties, and adding it to the methyl jasmonate composite fresh-keeping liquid can further enhance the fresh-keeping effect of the fresh-keeping liquid.

[0025] 5. The present invention sprays the blueberries with the composite fresh-keeping liquid after they are picked, which can not only preserve the blueberries, but also reduce the field heat and respiratory heat during blueberry picking; the blueberries sprayed with the composite fresh-keeping liquid are placed in a ventilated environment at 16-18° C., which further reduces the field heat and respiratory heat of the blueberries, while evaporating the moisture on the surface of the blueberry fruit, thereby improving the fresh-keeping effect of the blueberries. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a flow chart for preparing the methyl jasmonate composite fresh-keeping solution of the present invention;

[0027] Figure 2 A line graph showing changes in pulp hardness during storage of blueberries according to the present invention;

[0028] Figure 3 The bar graph of the change of blueberry decay rate during the blueberry storage process of the present invention;

[0029] Figure 4 The bar graph of the change of soluble solid content of blueberries during the storage process of blueberries of the present invention;

[0030] Figure 5 This is a line graph showing changes in blueberry SOD during storage of blueberries according to the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Flavonoids in the extracts of astragalus, licorice, honeysuckle and chrysanthemum have different degrees of antibacterial effects on a variety of pathogenic bacteria such as Bacillus subtilis, Escherichia coli, Aspergillus niger, etc., and can effectively inhibit the growth of microorganisms on the surface of fruits and vegetables and slow down the spoilage of fruits and vegetables; flavonoids have strong antioxidant properties and can remove free radicals produced by fruits and vegetables during storage, protect the integrity of fruit and vegetable cell membranes, and delay the aging process of fruits and vegetables; flavonoids can close the stomata of the fruit and vegetable epidermis, inhibit the respiration of fruits and vegetables, reduce the loss of water in fruits and vegetables by slowing down respiration, reduce the weight loss rate of fruits and vegetables during storage, and at the same time slow down the consumption of sugar content and other nutrients to maintain the quality and nutritional value of fruits and vegetables.

[0033] Polysaccharides in Astragalus, such as Astragalus polysaccharide, can form a protective film on the surface of fruits and vegetables, reduce the evaporation of water on the surface of fruits and vegetables, and maintain the texture and taste of fruits and vegetables; Licorice contains glycyrrhizic acid, glycyrrhizin and other active ingredients, which have multiple biological activities, such as anti-oxidation and antibacterial, and can protect the integrity of the cell membrane of fruits and vegetables, thereby delaying the aging and corruption of fruits and vegetables. Honeysuckle contains active ingredients such as luteolin, inositol, and volatile oils, which can bind to the cell membrane of microorganisms, destroy their cell structure or interfere with their metabolic process, prevent the nutrients in fruits and vegetables from being oxidized and destroyed, thereby maintaining the quality and taste of fruits and vegetables. At the same time, the active ingredients in honeysuckle have the function of regulating the physiological activity of fruits and vegetables. By regulating the respiration, metabolic process and other physiological processes of fruits and vegetables, the aging and corruption of fruits and vegetables can be further delayed. Inositol in honeysuckle can delay the shrinkage process of fruits and maintain the fullness and freshness of fruits. Chrysanthemum contains a variety of active ingredients such as chrysanthemum glycosides and polyphenol compounds, which can play an antibacterial and antioxidant role on fruits and vegetables, and delay the decay and deterioration of fruits and vegetables. The composite preservative solution is obtained by mixing the methyl jasmonate solution with the extracts made from the medicinal and edible substances astragalus, licorice, honeysuckle, and chrysanthemum, which overcomes the defects of the single methyl jasmonate solution, can effectively reduce the softening of blueberry fruits, delay their decay and deterioration, and improve their commodity value. At the same time, astragalus, licorice, honeysuckle, and chrysanthemum are medicinal and edible substances, which are safe and non-toxic.

[0034] The invention adopts ultrasonic extraction of astragalus, licorice, honeysuckle and chrysanthemum, controls the temperature, frequency and pH value of the ultrasonic solution, utilizes the cavitation effect, mechanical effect and thermal effect of the ultrasonic wave to rupture the cell walls of astragalus, licorice, honeysuckle and chrysanthemum, releases the effective ingredients, and thus improves the preservation effect of fruits and vegetables.

[0035] Cellulase can decompose cellulose in the cell walls of astragalus, licorice, honeysuckle and chrysanthemum, destroy the dense structure of the cell walls, and make it easier for flavonoids to be released from the cells; hemicellulase can hydrolyze hemicellulose connected to flavonoids, which is beneficial to the extraction of flavonoids; pectinase can decompose pectin in the cell walls of astragalus, licorice, honeysuckle and chrysanthemum, further destroy the cell structure and increase the dissolution rate of flavonoids. The mixture of cellulase, hemicellulase and pectinase can work synergistically to better destroy the cell walls of licorice and honeysuckle, increase the dissolution rate of effective ingredients such as glycyrrhizic acid in licorice and the extraction rate of effective ingredients such as inositol in honeysuckle, and thus improve the preservation effect of fruits and vegetables.

[0036] As a surfactant, lecithin can change the surface tension of the solution, making it easier to spread the preservative solution after spraying, thereby accelerating the drying speed of the preservative solution on the surface of fruits and vegetables; furthermore, lecithin has antioxidant properties, and adding it to the methyl jasmonate composite preservative solution can further enhance the preservation effect of the preservative solution.

[0037] During the application of the methyl jasmonate composite fresh-keeping liquid in the preservation of blueberries, the composite fresh-keeping liquid is sprayed on the blueberries after they are picked, so that the blueberries can be preserved and the field heat and respiratory heat during the picking of the blueberries can be reduced; the blueberries sprayed with the composite fresh-keeping liquid are placed in a ventilation treatment under the condition of 16-18° C., so that the field heat and respiratory heat of the blueberries are further reduced while the water on the surface of the blueberry fruits is evaporated, thereby improving the fresh-keeping effect of the blueberries.

[0038] The present invention also includes crushing the astragalus and licorice before weighing them, so that the particle size of the astragalus and licorice is 0.5-1.0 mm. Astragalus and licorice with too small particle size are prone to produce more powder during the extraction process, making it difficult to filter and centrifuge the extract, resulting in turbidity of the extract, affecting the color of blueberries when spraying blueberries, and easily causing nozzle clogging. On the contrary, when the particle size of astragalus and licorice is large, the extraction effect is not good, the effective ingredients in astragalus and licorice are not completely released, resulting in poor preservation effect.

[0039] like Figure 1 The present invention provides a method for preparing a methyl jasmonate composite fresh-keeping liquid, comprising the following steps:

[0040] Step 1, crushing Astragalus and licorice: crush Astragalus and licorice respectively with a grinder until the particle size of Astragalus and licorice is 0.5-1.0 mm; preparation of extract: weigh Astragalus, licorice, honeysuckle, chrysanthemum, and deionized water and place them in an ultrasonic device, then add cellulase, hemicellulase and pectinase, and acid-base regulator, perform ultrasonic extraction, filtration, and centrifugation to obtain the extract. Step 2, preparation of methyl jasmonate solution: dissolve methyl jasmonate and lecithin in ethanol first, stir and mix evenly, and then add deionized water to prepare a 45-50 μmol / L methyl jasmonate solution. Step 3, mix the methyl jasmonate solution and the extract in a certain volume ratio to obtain a methyl jasmonate composite preservative solution.

[0041] The raw materials used in the present invention are all commercially available raw materials.

[0042] Embodiment 1:

[0043] A method for preparing a methyl jasmonate composite fresh-keeping liquid comprises the following steps:

[0044] Step 1, crushing Astragalus and licorice: crush Astragalus and licorice respectively with a grinder until the particle size of Astragalus and licorice is 0.5mm; preparation of extract: weigh 35 parts by weight of Astragalus, 30 parts by weight of licorice, 12 parts by weight of honeysuckle, 5 parts by weight of chrysanthemum, and 150 parts by weight of deionized water and place them in an ultrasonic device, then add 0.3% of the total amount of deionized water enzyme preparation (cellulase, hemicellulase and pectinase are composed of a mass ratio of 2:1:1), acid-base regulator citric acid, adjust the pH value to 5.5, perform ultrasonic extraction, filter, and centrifuge to obtain the extract. The cellulase activity is 20U / mg, the hemicellulase activity is 3U / mg, and the pectinase activity is 3U / mg. The frequency of the ultrasonic device is 110Hz, the temperature is 35℃, the time is 40min, and the centrifugal speed is 2000rpm.

[0045] Step 2, preparation of methyl jasmonate solution: dissolve methyl jasmonate and lecithin in ethanol at a mass ratio of 3:1, stir and mix evenly, add deionized water to prepare a 45 μmol / L methyl jasmonate solution, and the volume concentration of ethanol is 2%.

[0046] Step 3: Mix the methyl jasmonate solution and the extract in a volume ratio of 1:3 to obtain a methyl jasmonate composite preservative solution.

[0047] The application of methyl jasmonate composite preservative liquid in the preservation of blueberries is processed by the following method and steps:

[0048] S1. The harvested blueberries are sprayed with a methyl jasmonate compound fresh-keeping liquid. The spraying amount of the methyl jasmonate compound fresh-keeping liquid is 2% of the mass of the blueberries to ensure that the surface of the blueberries is sprayed evenly.

[0049] S2. Place the sprayed blueberries at 16°C for 4 hours under ventilation, and then package them in polyethylene terephthalate boxes.

[0050] Embodiment 2:

[0051] A method for preparing a methyl jasmonate composite fresh-keeping liquid comprises the following steps:

[0052] Step 1, crushing Astragalus and licorice: crush Astragalus and licorice respectively with a grinder until the particle size of Astragalus and licorice is 1.0 mm; preparation of extract: weigh 40 parts by weight of Astragalus, 35 parts by weight of licorice, 15 parts by weight of honeysuckle, 8 parts by weight of chrysanthemum, and 160 parts by weight of deionized water and place them in an ultrasonic device, then add 0.5% of the total amount of deionized water enzyme preparation (cellulase, hemicellulase and pectinase are composed of a mass ratio of 2:1.2:1), acid-base regulator malic acid, adjust the pH value to 6.5, perform ultrasonic extraction, filtration, and centrifugation to obtain an extract. The cellulase activity is 25U / mg, the hemicellulase activity is 5U / mg, and the pectinase activity is 5U / mg. The frequency of the ultrasonic device is 115Hz, the temperature is 40℃, the time is 45min, and the centrifugal speed is 2200rpm.

[0053] Step 2, preparation of methyl jasmonate solution: dissolve methyl jasmonate and lecithin in ethanol at a mass ratio of 3:1, stir and mix evenly, add deionized water to prepare a 50 μmol / L methyl jasmonate solution, and the volume concentration of ethanol is 2.5% to ensure uniform spraying on the surface of blueberry fruit.

[0054] Step 3: Mix the methyl jasmonate solution and the extract in a volume ratio of 1:3.5 to obtain a methyl jasmonate composite preservative solution.

[0055] The application of methyl jasmonate composite preservative liquid in the preservation of blueberries is processed by the following method and steps:

[0056] S1. The harvested blueberries are sprayed with a methyl jasmonate composite fresh-keeping liquid, wherein the spraying amount of the methyl jasmonate composite fresh-keeping liquid is 3% of the mass of the blueberries.

[0057] S2. Place the sprayed blueberries at 18°C ​​for 5 hours under ventilation, and then package them in polyethylene terephthalate boxes.

[0058] Comparative Example 1:

[0059] The difference from Example 1 is that the leaching liquid in Example 1 is removed.

[0060] Comparative Example 2:

[0061] The difference from Example 1 is that the lecithin in Example 1 is removed.

[0062] Comparative Example 3:

[0063] The difference from Example 1 is that the extract of Example 1 is prepared without ultrasonic extraction, and astragalus, licorice, honeysuckle, chrysanthemum and deionized water are directly extracted at a constant temperature of 35° C. for 40 min.

[0064] Comparative Example 4:

[0065] The difference from Example 1 is that the cellulase, hemicellulase and pectinase in Example 1 are removed.

[0066] Comparative Example 5:

[0067] The difference from Example 1 is that the cellulase in Example 1 is removed.

[0068] Comparative Example 6:

[0069] The difference from Example 1 is that the hemicellulase in Example 1 is removed.

[0070] Comparative Example 7:

[0071] The difference from Example 1 is that the pectinase in Example 1 is removed.

[0072] The extracts prepared in Examples 1 and 2 and Comparative Examples 3, 4, 5, 6 and 7 were measured for total flavonoids in the extracts according to SN / T4592-2016 "Determination of total flavonoids in exported foods", the inositol in the extracts was measured according to GB 5009.270-2023 "Determination of inositol in foods", and the glycyrrhizic acid in the extracts was measured according to GB / T22248-2008 "Determination of glycyrrhizic acid in health foods". The results are shown in Table 1.

[0073] Table 1: Active ingredient content in the extract

[0074] Total flavonoids (%) Inositol (mg / 100g) Glycyrrhizic acid (g / kg) Embodiment 1 0.09 0.145 0.098 Embodiment 2 0.10 0.152 0.102 Comparative Example 3 0.07 0.123 0.087 Comparative Example 4 0.05 0.087 0.062 Comparative Example 5 0.06 0.115 0.075 Comparative Example 6 0.07 0.106 0.082 Comparative Example 7 0.06 0.122 0.078

[0075] As shown in Table 1, the total flavonoids, inositol and glycyrrhizic acid in Example 1 and Example 2 are relatively high. The total flavonoids content in the extract of Example 1 is 22.2%, 44.4%, 33.3%, 22.2% and 33.3% higher than that in Comparative Examples 3, 4, 5, 6 and 7, respectively. The inositol content in the extract of Example 1 is 15.2%, 40.0%, 20.7%, 26.9% and 15.9% higher than that in Comparative Examples 3, 4, 5, 6 and 7, respectively. The glycyrrhizic acid content in the extract of Example 1 is 11.2%, 36.7%, 23.5%, 16.3% and 20.4% higher than that in Comparative Examples 3, 4, 5, 6 and 7, respectively.

[0076] It can be seen that ultrasonic extraction can use the cavitation effect and mechanical effect of ultrasound to break the cell walls of Astragalus, Licorice, Honeysuckle and Chrysanthemum to release effective active ingredients. Cellulase can decompose the cellulose in the cell walls of Astragalus, Licorice, Honeysuckle and Chrysanthemum, destroy the dense structure of the cell walls, and make it easier for flavonoids to be released from the cells; hemicellulase can hydrolyze the hemicellulose connected to flavonoids, which is beneficial to the extraction of flavonoids; pectinase can decompose the pectin in the cell walls of Astragalus, Licorice, Honeysuckle and Chrysanthemum, further destroy the cell structure and increase the dissolution rate of flavonoids. The mixture of cellulase, hemicellulase and pectinase can work synergistically to better destroy the cell walls of Licorice and Honeysuckle, and increase the dissolution rate of effective ingredients such as glycyrrhizic acid in Licorice and the extraction rate of effective ingredients such as inositol in Honeysuckle.

[0077] The blueberries were treated with the fresh-keeping liquid prepared in Examples 1 and 2 and Comparative Examples 1, 2, 3 and 4 and then packed into polyethylene terephthalate packaging boxes, each box of blueberries weighing (125±10) g, and stored at a temperature of (20±0.5)°C and a humidity of (75-80)%RH. Samples were taken every 2 days, and the index on day 0 was measured using the blueberries treated with low temperature ventilation on the day of picking. The CK group was not treated with the fresh-keeping liquid, but was directly packaged after low temperature ventilation treatment. The packaging and storage methods of the blueberries in the CK group were the same as those in Example 1.

[0078] Figure 2 To investigate the hardness changes of blueberries, a texture analyzer was used to measure the hardness of the fruit. A probe with a diameter of 8 mm was selected, the measuring depth was 7 mm, and the measuring speed was 0.5 mm / s. Each measurement was performed at the equator of the fruit. The hardness of the blueberry pulp was measured after removing the peel. The results of the blueberry pulp hardness were expressed in Newton (N).

[0079] Fruit hardness is an indicator of fruit maturity and storage characteristics, such as Figure 2As shown, on the 0th day, the blueberry pulp hardness of the CK group, Examples 1, 2, and Comparative Examples 1, 2, 3, and 4 were 0.36N, 0.38N, 0.38N, 0.37N, 0.36N, 0.36N, and 0.38N, respectively. In the early stage of storage, the pulp hardness of blueberries in each group showed a rapid downward trend. When the blueberries were stored for 6 days, the blueberry pulp hardness of the CK group, Examples 1, 2, and Comparative Examples 1, 2, 3, and 4 was Compared with the day 0, the hardness of the blueberries decreased by 28.4%, 18.3%, 20.4%, 31.3%, 26.6%, 23.9% and 27.4% respectively. When the blueberries were stored for 10 days, the hardness of the blueberry pulp treated by the CK group, Examples 1 and 2 and Comparative Examples 1, 2, 3 and 4 were 0.18N, 0.25N, 0.24N, 0.20N, 0.21N, 0.22N and 0.21N respectively. It can be seen that the blueberries treated with methyl jasmonate, lecithin and the extract can effectively delay the decline of the hardness of the blueberries and delay the softening of the blueberries. At the same time, the use of ultrasonic treatment during the extraction process of the extract, and the addition of cellulase, hemicellulase and pectinase are beneficial to the release of effective active ingredients in astragalus, licorice, honeysuckle and chrysanthemum, and improve their fresh-keeping effect.

[0080] Figure 3 The decay rate of blueberries was determined by sensory evaluation. If there was any spot on the surface of the fruit where skin juice leaked out or mold was visible to the naked eye, it was recorded as decayed. Each time the decay rate was measured, 100 fruits were selected, and the rotten fruits were selected and calculated according to the following formula:

[0081]

[0082] Where: N0-the number of rotten blueberry fruits; N-the total number of blueberry fruits.

[0083] Blueberry fruit has a high water content and is not protected by a tough peel. In addition, the pedicle is injured after picking and is infected by pathogens. It is easy to rot during storage, making the fruit lose its edible value. Therefore, the rot rate is an important indicator to measure the quality of the fruit. Figure 3 As shown, the decay rate of blueberries in each group after harvesting showed an upward trend, the decay rate was low in the first two days, and the decay rate rose rapidly from the 4th day. After storage for 10 days, the decay rates of blueberries in the CK group, Examples 1 and 2, and Comparative Examples 1, 2, 3, and 4 reached 23.24%, 12.29%, 12.74%, 16.35%, 15.41%, 15.70%, and 15.92%, respectively. On the 10th day, the decay rates of blueberries in the CK group and Comparative Examples 1, 2, 3, and 4 were 47.1%, 24.9%, 20.3%, 21.7%, and 22.8% higher than those in Example 1, respectively. It can be seen that blueberries treated with methyl jasmonate, lecithin, and extract can effectively reduce the decay rate of blueberries and improve the quality and commercial value of blueberries.

[0084] Figure 4 To investigate the changes in soluble solids content during storage of blueberries, a handheld sugar meter was used to measure the soluble solids content. Soluble solids are an important criterion for evaluating the quality of blueberries. Figure 4 As shown, the soluble solids showed a trend of first increasing and then decreasing. On the 10th day of storage, the soluble solids content of blueberries in the CK group, Example 1, Example 2, and Comparative Examples 1, 2, 3, and 4 were 9.03%, 10.13%, 9.97%, 9.40%, 9.53%, 9.43%, and 9.30%, respectively, which were decreased by 16.4%, 10.3%, 12.6%, 14.0%, 13.3%, 15.0%, and 15.5%, respectively, compared with the 0th day. During the storage process, the pectin, starch, cellulose and other components in the blueberries were decomposed into soluble solids by the corresponding enzymes, but these soluble solids were subsequently consumed by the respiration of the blueberries. In the early stage of storage, the soluble solids formed by ripening of blueberries are greater than the soluble solids consumed by respiration, and the soluble solids show an upward trend. As the storage time increases, the soluble solids formed are gradually less than the soluble solids consumed by respiration, and the content of soluble solids shows a downward trend. Blueberries treated with methyl jasmonate, lecithin, and extract can effectively delay the decline in the soluble solids content of blueberries and improve the quality of blueberries.

[0085] Figure 5 The changes of superoxide dismutase (SOD) during blueberry storage, SOD activity is expressed as U / g. The balance between SOD activities is crucial to the survival of blueberry cells during storage. The accumulation of superoxide free radicals in blueberry fruits can easily cause blueberry cell damage. For self-protection, the body will produce a defense mechanism, and the related SOD activity will change. Figure 5 As shown, the activity of SOD in blueberry increases rapidly in the early stage of storage, but gradually decreases in the later stage of storage, and the antioxidant capacity of blueberry fruit will gradually weaken. When stored to the 4th day, the SOD values ​​of blueberries treated with CK group and comparative examples 1, 2, 3, and 4 reached peak values, which were 0.992U / g, 0.906U / g, 0.880U / g, 0.894U / g and 0.886U / g, respectively. The SOD values ​​of blueberries treated with Example 1 and Example 2 reached peak values ​​on the 6th day, which were 0.894U / g and 0.886U / g, respectively. As the fruit matures and ages, the metabolic activity inside the fruit gradually weakens, resulting in a decrease in the activity of antioxidant enzymes. The treatment of blueberries with methyl jasmonate composite preservative solution effectively delayed the appearance of SOD peak, maintained a high SOD activity, and improved the ability of blueberries to scavenge hydrogen peroxide and superoxide free radicals.

[0086] In summary, the present invention adds medicinal and edible homologous substances such as astragalus, liquorice, honeysuckle, chrysanthemum extract and lecithin to the methyl jasmonate composite fresh-keeping liquid, and sprays blueberries with this fresh-keeping liquid, which can effectively slow down the decline of hardness and soluble solids during the storage of blueberries, reduce the problems of blueberries being easily softened, rotten and deteriorated after being picked, extend the shelf life of blueberries, and improve their commodity value. The methyl jasmonate composite fresh-keeping liquid is sprayed on the blueberries after the blueberries are picked, which can not only keep the blueberries fresh, but also reduce the field heat and respiratory heat when the blueberries are picked. And this methyl jasmonate composite fresh-keeping liquid is safe and non-toxic, simple to prepare, and easy to promote.

[0087] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all included in the protection scope of the present invention.

Claims

1. A method for preparing a methyl jasmonate composite fresh-keeping liquid, characterized in that: The following steps are involved: Step 1, preparation of extract: weigh 35-40 parts by weight of Astragalus, 30-35 parts by weight of Licorice, 12-15 parts by weight of Honeysuckle, 5-8 parts by weight of Chrysanthemum, and 150-160 parts by weight of deionized water, place them in an ultrasonic device, then add enzyme preparation and acid-base regulator, perform ultrasonic extraction, filter, and centrifuge to obtain an extract; Step 2, preparation of methyl jasmonate solution: dissolving methyl jasmonate and lecithin in ethanol, mixing evenly, and then adding deionized water to prepare a 45-50 μmol / L methyl jasmonate solution; Step 3, mixing the methyl jasmonate solution and the extract to obtain a methyl jasmonate composite fresh-keeping solution; The enzyme preparation is composed of cellulase, hemicellulase and pectinase in a mass ratio of 2:1 to 1.2:1, the amount of the enzyme preparation added is 0.3 to 0.5% of the total amount of deionized water, the cellulase activity is 20 to 25 U / mg, the hemicellulase activity is 3 to 5 U / mg, and the pectinase activity is 3 to 5 U / mg; The volume ratio of the methyl jasmonate solution and the extract when mixed is 1:3-3.

5.

2. The method for preparing a methyl jasmonate composite fresh-keeping liquid according to claim 1, characterized in that: Before weighing the astragalus and licorice, the method further comprises: crushing the astragalus and licorice to make the particle sizes of the astragalus and licorice be 0.5-1.0 mm.

3. The method for preparing a methyl jasmonate composite fresh-keeping liquid according to claim 1, characterized in that: The ultrasonic equipment has a frequency of 110-115 Hz, a temperature of 35-40° C., and a time of 40-45 min.

4. The method for preparing a methyl jasmonate composite fresh-keeping liquid according to claim 1, characterized in that: The acid-base regulator is any one of citric acid and malic acid or a mixture of the two substances, and the pH value is adjusted to 5.5-6.

5.

5. The method for preparing a methyl jasmonate composite fresh-keeping liquid according to claim 1, characterized in that: The centrifugal speed is 2000-2200 rpm.

6. The method for preparing a methyl jasmonate composite fresh-keeping liquid according to claim 1, characterized in that: The purity of the methyl jasmonate is 98%, and the mass ratio of methyl jasmonate to lecithin is 3:

1.

7. The method for preparing a methyl jasmonate composite fresh-keeping liquid according to claim 1, characterized in that: The volume concentration of the ethanol is 2-2.5%.

8. Use of the methyl jasmonate composite fresh-keeping solution prepared according to the method for preparing the methyl jasmonate composite fresh-keeping solution according to any one of claims 1 to 7 in the preservation of blueberries.

9. Use of the methyl jasmonate composite fresh-keeping liquid according to claim 8 in blueberry preservation, characterized in that: The blueberry preservation is processed by the following method steps: S1. Spraying the harvested blueberries with a methyl jasmonate composite fresh-keeping solution, wherein the amount of the methyl jasmonate composite fresh-keeping solution sprayed is 2 to 3% of the mass of the blueberries; S2. Place the sprayed blueberries at 16-18°C for 4-5 hours under ventilation, and then package them in polyethylene terephthalate boxes.

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