Compound fresh-keeping agent and method for delaying postharvest fruit and vegetable yellowing

Abstract

The application discloses a kind of postharvest fruit and vegetable chlorosis delaying composite preservative and method, the effective component of the composite preservative includes the concentration of 10-60ppm chondroitin sulfate, the concentration of 10-60ppm heparin and the concentration of 10-60ppm hyaluronic acid.The application uses chondroitin sulfate, heparin and hyaluronic acid as composite preservative to treat postharvest citron, and shows synergistic effect of delaying chlorophyll content reduction of citron, inhibiting fruit chlorosis, so as to effectively delay postharvest citron shelf life, and the composite preservative of the application has the characteristics of green and efficient, effective components can be completely water-soluble, and environmental pollution cannot be generated.

Description

Technical Field

[0001] The present invention belongs to the technical field of fruit storage and preservation, and more particularly, to a composite preservative and a method for delaying the chlorosis and yellowing of post-harvest citron. Background Art

[0002] Citron, also known as perfumed lemon, is native to the subtropical and warm temperate regions of Asia and is widely cultivated in southern China, with distinct regional characteristics. Rich in essential oils and antioxidant, aging-related secondary metabolites, citron is a source of traditional Chinese medicine (Chhikara et al., 2018). In recent years, with the development of milk tea and catering, citron has become increasingly popular as a source of aroma and flavor, and market demand has continued to increase. Citron is typically harvested when green and ripe. During storage and transportation, the peel gradually fades and yellows, and its aroma and flavor evaporate and dissipate, seriously affecting its commercial value from field to table (Taghvaeefard et al., 2021). Therefore, exploring green and efficient storage and preservation methods to extend the shelf life of citron after harvest and reduce losses and preserve its quality is crucial for enhancing its market value.

[0003] During postharvest storage, chlorophyll degradation, peel chlorosis and yellowing, and reduced aroma and flavor are the main factors affecting citron quality and market value. Researchers have been able to slow the chlorosis and senescence of bananas and Chinese cabbage to a certain extent through modified atmosphere packaging and synthetic cytokinins. However, there is currently a lack of research reports on postharvest storage and preservation of citron, and green and efficient postharvest storage and preservation technologies for citron have not been widely explored. Therefore, it is of great significance to explore green and efficient storage and preservation methods that can address postharvest chlorosis and yellowing of citron and slow the rapid degradation of chlorophyll, especially to screen for safe and effective preservatives with natural activity from animal and plant sources. Summary of the Invention

[0004] Based on this, the object of the present invention is to provide a composite preservative and its application, as well as a method for delaying the chlorosis and yellowing of post-harvest citron. The composite preservative of the present invention can effectively delay the chlorosis and yellowing of post-harvest citron and inhibit the reduction of chlorophyll content in citron.

[0005] The technical solutions for achieving the above-mentioned invention objectives include the following.

[0006] A first aspect of the present invention provides a composite preservative, wherein the effective ingredients of the composite preservative include chondroitin sulfate at a concentration of 10 to 60 ppm and heparin at a concentration of 10 to 60 ppm.

[0007] A second aspect of the present invention provides use of the composite preservative in delaying chlorosis and yellowing of post-harvest fruits and vegetables.

[0008] The third aspect of the present invention provides a method for delaying the chlorosis and yellowing of post-harvest citron, comprising the following steps: soaking, coating or spraying the green citron fruits that are 80% mature after harvest with the above-mentioned composite preservative.

[0009] The present invention has the following beneficial effects:

[0010] The present invention adopts a compound of chondroitin sulfate, heparin and hyaluronic acid as a composite preservative to treat post-harvest citron, showing a synergistic effect of delaying the reduction of chlorophyll content in citron and inhibiting the chlorosis and yellowing of the fruit, thereby effectively delaying the post-harvest shelf life of citron. In addition, the composite preservative of the present invention is green and efficient, and the active ingredients are all completely water-soluble, without causing environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 These are actual pictures of fresh citron fruits harvested on day 0 and citron fruits stored for 36 days in the control group in the test example of the present invention; the scale bar in the figure is 1 cm.

[0012] Figure 2 The figure shows the citron fruits stored for 36 days after being treated in various experimental groups in the test examples of the present invention; CK: control; HP: heparin; CS: chondroitin sulfate; HA: hyaluronic acid; the scale bar in the figure is 1 cm.

[0013] Figure 3 The yellowing index results of citron fruits stored for 36 days after being treated in various experimental groups in the test examples of the present invention; CK: control; HP: heparin; CS: chondroitin sulfate; HA, hyaluronic acid; different letters in the figure indicate significant differences between the groups at the p < 0.05 level.

[0014] Figure 4 The colorimetric results of citron fruits stored for 36 days after being treated in various experimental groups in the test examples of the present invention; CK: control; HP: heparin; CS: chondroitin sulfate; HA, hyaluronic acid; different letters in the figure indicate significant differences between the groups at the p < 0.05 level.

[0015] Figure 5 The chlorophyll content results of citron fruits stored for 36 days after being treated in various experimental groups in the test examples of the present invention; CK: control; HP: heparin; CS: chondroitin sulfate; HA, hyaluronic acid; different letters in the figure indicate significant differences between the groups at the p < 0.05 level. DETAILED DESCRIPTION

[0016] To facilitate understanding of the present invention, the present invention will be described more fully below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the present disclosure more thorough and comprehensive.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety.

[0018] The experimental methods in the following examples, unless otherwise specified, are generally carried out according to the conventional conditions or according to the conditions recommended by the manufacturers. The various common chemical reagents used in the examples are commercially available products.

[0019] Based on years of research experience in fruit and vegetable preservation, the inventors of the present application found through a large number of experiments that chondroitin sulfate and heparin compounded as a preservative can effectively delay the postharvest citrus chlorophyll degradation, fruit yellowing and other senescence processes. On this basis, the addition of hyaluronic acid, the three components of the compound preservative treated postharvest citrus, show synergistic effect of delaying the decrease of chlorophyll content in citrus and inhibiting fruit yellowing. After 36 days of storage, the citrus fruit can still maintain a good green skin, and the yellowing index decreases significantly (from 81% to 54.5%); significantly inhibits the rapid decrease of color angle, and can still maintain at 108° after 36 days of postharvest (the color angle of citrus green period is 121°); significantly synergistically delays chlorophyll degradation, and the chlorophyll content is still as high as 47.3 mg kg -1 (fresh citrus chlorophyll is 64 mg kg -1 ). Therefore, using the compound preservative of the present application to treat postharvest citrus can effectively delay the postharvest shelf life of citrus. After treatment with the compound preservative, combined with modified atmosphere packaging bags, the loss during postharvest transportation and supermarket sales can be reduced. In addition, the effective components of the compound preservative in the present application, chondroitin sulfate, heparin and hyaluronic acid, are natural polysaccharide active substances from scallops and other sources, which have the functions of water retention, antioxidant, etc., can effectively delay aging, inhibit chlorophyll degradation, etc., have the characteristics of green and high efficiency, and the effective components can be completely water-soluble, without environmental pollution.

[0020] In some embodiments of the present application, a compound preservative is disclosed, the effective components of which include chondroitin sulfate with a concentration of 10-60 ppm and heparin with a concentration of 10-60 ppm.

[0021] In some embodiments, the concentrations of chondroitin sulfate and heparin are both 15-45 ppm.

[0022] In some embodiments, the concentrations of chondroitin sulfate and heparin are both 18-35 ppm.

[0023] In some embodiments, the effective components of the composite preservative further include hyaluronic acid, and the concentration of the hyaluronic acid in the composite preservative is 10-60 ppm.

[0024] In some embodiments, the composite preservative is composed of chondroitin sulfate with a concentration of 18-22 ppm, heparin with a concentration of 18-22 ppm, and hyaluronic acid with a concentration of 18-22 ppm.

[0025] In some embodiments of the present application, the use of the composite preservative in delaying the yellowing of postharvest fruits and vegetables is disclosed.

[0026] In some embodiments, the fruits and vegetables are citrons.

[0027] In some embodiments of the present application, a method for delaying the yellowing of postharvest citron fruits is disclosed, which comprises the following steps: picking green citron fruits at 80% maturity, selecting fruits with uniform size and no mechanical damage on the surface, coating the composite preservative on the surface of the citron fruits by immersion, application or spraying, air-drying the surface moisture, and then storing at room temperature at 15-22℃.

[0028] In some embodiments, the soaking time is 5-20 min.

[0029] In some embodiments, the soaking time is 8-12 min.

[0030] In the following examples, the citrons are green citron fruits at 80% maturity picked from the citron planting base in Zengcheng, Guangzhou, Guangdong Province; chondroitin sulfate, heparin and hyaluronic acid are purchased from Beijing Solabio Biotech Co., Ltd.; polyethylene modified atmosphere packaging bags (30 μm thick) are purchased from Shanghai Fumeng New Material Technology Co., Ltd. Adjustable constant temperature box: -5-50℃, Thermo Scientific. Colorimeter: CR-400 handheld colorimeter (Minolta Camera Co., Ltd., Osaka, Japan). Spectrophotometer: UV-2600 ultraviolet spectrophotometer (Shimadzu, Japan).

[0031] The present application is described in detail below in combination with the accompanying drawings and specific examples.

[0032] Example 1: A composite preservative and a method for delaying the yellowing of postharvest citron fruits

[0033] The composite preservative provided in this example has effective components of chondroitin sulfate with a concentration of 45 ppm and heparin with a concentration of 15 ppm.

[0034] The preparation method of the composite preservative provided in this embodiment comprises the following steps: dissolving chondroitin sulfate and heparin in water to a concentration of 45 ppm and 15 ppm, respectively.

[0035] This embodiment also provides a method for delaying the chlorosis and yellowing of post-harvest citron, comprising the following steps:

[0036] Pick 80% ripe green citron fruits, select fruits of uniform size and without mechanical damage on the surface, soak them in the composite preservative of this embodiment for 10 minutes, air-dry the surface moisture, and package them in 30 μm thick polyethylene modified atmosphere fresh-keeping bags and store them at 22°C.

[0037] Example 2 A composite preservative and a method for delaying the chlorosis and yellowing of post-harvest citrons

[0038] The composite preservative provided in this embodiment has active ingredients including chondroitin sulfate at a concentration of 20 ppm, heparin at a concentration of 20 ppm, and hyaluronic acid at a concentration of 20 ppm.

[0039] The preparation method and use method of the composite preservative provided in this embodiment are the same as those in Example 1.

[0040] Example 3 A composite preservative and a method for delaying the chlorosis and yellowing of post-harvest citrons

[0041] The composite preservative provided in this embodiment has active ingredients including chondroitin sulfate at a concentration of 30 ppm, heparin at a concentration of 40 ppm, and hyaluronic acid at a concentration of 10 ppm.

[0042] The preparation method and use method of the composite preservative provided in this embodiment are the same as those in Example 1.

[0043] Example 4 A composite preservative and a method for delaying the chlorosis and yellowing of post-harvest citrons

[0044] The composite preservative provided in this embodiment has active ingredients including chondroitin sulfate at a concentration of 18 ppm, heparin at a concentration of 50 ppm, and hyaluronic acid at a concentration of 25 ppm.

[0045] The preparation method and use method of the composite preservative provided in this embodiment are the same as those in Example 1.

[0046] Experimental Example Effect of the composite preservative of the present invention on chlorosis and yellowing of post-harvest citron fruit

[0047] 1. Experimental Methods

[0048] Citron fruits at approximately 80% maturity were picked for post-harvest storage and preservation research. Citron fruits of uniform size, without obvious scars, and free of pests and diseases were selected and randomly divided into 8 groups:

[0049] Control check: The fruits were soaked in clean water, taken out and naturally air-dried, and then packaged in polyethylene modified atmosphere fresh-keeping bags (30 μm thick).

[0050] Experimental group 1: The fruits were soaked in 60 ppm heparin solution (HP), taken out, naturally air-dried for surface moisture, and packaged in polyethylene modified atmosphere fresh-keeping bags (30 μm thick).

[0051] Experimental group 2: The fruits were soaked in 60 ppm chondroitin sulfate solution (CS), taken out, naturally air-dried for surface moisture, and packaged in polyethylene modified atmosphere fresh-keeping bags (30 μm thick).

[0052] Experimental group 3: The fruits were soaked in 60 ppm hyaluronic acid solution (HA), taken out and naturally air-dried for surface moisture, and then packaged in polyethylene modified atmosphere fresh-keeping bags (30 μm thick).

[0053] Experimental Group 4: The fruits were treated by soaking in 30 ppm heparin (HP) and 30 ppm chondroitin sulfate (CS) solution, and then taken out to air-dry the surface moisture and packaged in polyethylene modified atmosphere fresh-keeping bags (30 μm thick).

[0054] Experimental Group 5: The fruits were treated by soaking in 30 ppm heparin (HP) and 30 ppm hyaluronic acid (HA) solution, and then taken out to air-dry the surface moisture and packaged in polyethylene modified atmosphere fresh-keeping bags (30 μm thick).

[0055] Experimental Group 6: The fruits were treated by soaking in 30 ppm chondroitin sulfate (CS) solution and 30 ppm hyaluronic acid (HA) solution, and then taken out to air-dry the surface moisture and packaged in polyethylene modified atmosphere fresh-keeping bags (30 μm thick).

[0056] Experimental Group 7: The fruits were soaked in 20 ppm heparin, 20 ppm chondroitin sulfate solution, and 20 ppm hyaluronic acid solution. After being taken out, the surface moisture was naturally air-dried and the fruits were packaged in polyethylene modified atmosphere fresh-keeping bags (30 μm thick).

[0057] The eight groups of fruits were soaked for 10 minutes each, air-dried at room temperature, and then stored at room temperature (22°C-24°C). Citron fruits were observed for post-ripening and senescence at 0, 10, 20, 30, and 36 days (the control group was essentially completely yellow). Chlorosis and yellowing were recorded, and changes in fruit color and chlorophyll content were measured.

[0058] 2. Experimental Results

[0059] 1. Yellowing index

[0060] The yellowing grade standard is set based on the size of the peel surface where the color of each fruit changes:

[0061] 0, turquoise;

[0062] 1, 0-1 / 4 yellowing area;

[0063] 2, 1 / 4-1 / 2 yellowing area;

[0064] 3, 1 / 2-3 / 4 yellowing area;

[0065] 4.>3 / 4 yellowing area.

[0066] The yellowing index calculation formula is as follows:

[0067] Yellowing index = ∑ (yellowing grade × the proportion of fruits of each yellowing grade to the total fruits).

[0068] Figure 1 These are pictures of fresh citrons sampled on day 0 and after 36 days of storage as a control. The fresh citrons are bluish green in color. Except for slight yellow spots on the fruits due to light protection, the surface of the fruits is uniformly glossy and bluish green. After 36 days of storage at room temperature, the fruits in the control group are almost fully mature and yellow. Figure 2 The pictures of citron fruits in each treatment group after 36 days of storage are shown below. Figure 3 Yellowing index of fruits in each treatment group after 36 days of storage.

[0069] from Figures 2 and 3 Compared with the control group (CK) (almost chlorotic, with a yellowing rate of 81%), heparin (HP, experimental group 1), chondroitin sulfate (CS, experimental group 2), and hyaluronic acid (HA, experimental group 3) all delayed the chlorosis process to a certain extent (yellowing rates of 71.6%, 67.5%, and 71.4%, respectively), with chondroitin sulfate (experimental group 2) showing the greatest effect. Combinations of two preservatives (experimental groups 5-6) were comparable in delaying post-ripening chlorosis to those treated with either preservative alone (yellowing rates of 68.9% and 65.6%, respectively). The combined treatment of heparin and chondroitin sulfate (experimental group 4) was significantly more effective than either preservative alone or experimental groups 5-6 (yellowing rate of 60.4%). Citron fruits treated with a combination of heparin, chondroitin sulfate, and hyaluronic acid (HP+CS+HA experimental group 7) maintained their green skin well after 36 days of storage, with a slow increase in the yellowing index (54.5%), demonstrating a significant preservation effect in inhibiting chlorosis and yellowing of citron fruits.

[0070] 2. Determination of fruit color change

[0071] After 36 days of storage, citron fruits from each treatment group were randomly selected to measure the color change of the fruit. 6 to 8 fruits were measured in each group. A colorimeter was used to measure three points evenly on the fruit body of each fruit. The CIE mode was selected for the measurement, and the L*, a* and b* values ​​were recorded. The chromaticity angle (°) was calculated. The chromaticity angle can reflect the color change, and 90° is the critical value for complete change. The results are shown in Figure 2. Figure 4 shown.

[0072] Figure 4 The results showed that the hue angle of citron was 121° when green, but it had essentially turned yellow after 36 days of storage, reaching a hue angle of 93.8°. While a single preservative could somewhat slow the decline in hue angle, it was significantly less effective than a combination of two. The combination of three significantly slowed the rapid decline in hue angle, maintaining it at 108° 36 days after harvest (experimental group 7).

[0073] 3. Chlorophyll content determination

[0074] After 36 days of storage, the skin of citron fruits from each treatment group was randomly sampled and the changes in chlorophyll content were measured. 6 to 8 fruits were measured in each group.

[0075] The peels of each treatment group were collected, quickly frozen in liquid nitrogen, and stored at -80°C. After all the peels were collected, they were crushed. 0.5g of peel powder was weighed from each group and extracted with 10mL of 80% acetone for 24h. The filtrate was then filtered and collected. The absorbance values ​​were measured at 663nm and 645nm using a UV-2600 spectrophotometer, and the chlorophyllin content was calculated in mg / kg. -1 Fresh sample.

[0076] The results are as follows Figure 5 As shown in Figure 2, the chlorophyll content of citron decreases gradually with the yellowing during storage. The chlorophyll content of fresh citron is as high as 64 mg kg -1 Fresh sample, after 36 days of storage, was only 14.8 mg kg -1 (Control group CK). The three preservative ingredients applied alone can delay the decrease of chlorophyll content, but the effect is limited; the combination of two can further enhance the effect, and the degradation of chlorophyll is significantly delayed. After 36 days of storage, the chlorophyll content is 39.9 mg kg -1 (Experimental group 4), 28.6 mg kg -1 (experimental group 5) and 35.6 mg kg -1 (Experimental Group 6); The combination of the three preservative ingredients can significantly synergistically delay the degradation of chlorophyll. After 36 days of storage, the chlorophyll content is still as high as 47.3 mg kg -1 (Experimental group 7).

[0077] The results of this example demonstrate that heparin and chondroitin sulfate, particularly heparin, chondroitin sulfate, and hyaluronic acid, as composite preservatives, can synergistically delay the post-ripening and senescence of citron fruit during room-temperature storage. This is demonstrated by slowing the chlorosis and yellowing of postharvest citron fruit and inhibiting the rapid decrease in chromaticity and chlorophyll content. The composite preservative of this invention is of great significance for studying the mechanisms regulating chlorosis and softening of postharvest citron fruit through antioxidant measures, as well as for developing preservation technologies.

[0078] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for delaying the chlorosis and yellowing of post-harvest citron, characterized in that: The following steps are involved: Green citrons that are eight-tenths mature after harvest are soaked, coated or sprayed with a composite preservative, wherein the active ingredients of the composite preservative are composed of chondroitin sulfate with a concentration of 10-60 ppm, heparin with a concentration of 10-60 ppm, and hyaluronic acid with a concentration of 10-60 ppm.

2. The method for delaying chlorosis and yellowing of post-harvest citron according to claim 1, characterized in that: The effective components of the composite preservative consist of chondroitin sulfate with a concentration of 18-22 ppm, heparin with a concentration of 18-22 ppm, and hyaluronic acid with a concentration of 18-22 ppm.

3. The method for delaying chlorosis and yellowing of post-harvest citron according to claim 1, characterized in that: The soaking time is 5 to 20 minutes.

4. The method for delaying chlorosis and yellowing of post-harvest citron according to claim 3, characterized in that: The soaking time is 8 to 12 minutes.

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