Valerian oil slow-release fumigant based on microcapsules and application of valerian oil slow-release fumigant in delay of postharvest yellowing of broccoli

Abstract

The invention discloses a valerian oil slow-release fumigant based on microcapsules and application of the valerian oil slow-release fumigant in delaying yellowing of broccoli after picking, and belongs to the technical field of green preservation of agricultural products. The preparation method of the microcapsule-based valerian oil slow-release fumigant comprises the following steps: mixing a sodium alginate solution, a surfactant and valerian oil to form primary emulsion, and homogenizing the primary emulsion to obtain a sodium alginate-valerian oil emulsion; dropwise adding the sodium alginate-valerian oil emulsion into a calcium chloride solution to obtain the valerian oil slow-release fumigant based on the microcapsules. After being treated by the microcapsule-based valerian oil slow-release fumigant, the shelf life of broccoli can be prolonged to 5 days, and the effective concentration maintaining time of the microcapsule-based valerian oil slow-release fumigant can be prolonged to 72 hours.

Description

Technical Field

[0001] This invention belongs to the field of green preservation technology for agricultural products, and more specifically relates to a microcapsule-based slow-release fumigant of valerian oil and its application in delaying postharvest yellowing of broccoli. Background Technology

[0002] Broccoli (Brassica oleracea var. italica) undergoes rapid chlorophyll degradation after harvest due to its vigorous respiration and metabolism, easily turning yellow within 48-72 hours, resulting in a significant decrease in commercial value. Currently used preservation techniques include:

[0003] Essential oils can be directly steamed for preservation: such as oregano oil and tea tree oil, which inhibit bacteria and oxidation through volatile components. However, they have problems such as a narrow concentration window (too high a concentration can cause phytotoxicity, while too low a concentration can have poor effects) and a short duration of action (>90% of the active ingredients evaporate within 12 hours).

[0004] Physical encapsulation technology: Most existing technologies use chitosan, cyclodextrin, etc. to encapsulate essential oils to make sprays, but they have defects such as low inclusion rate, high humidity disintegration, and severe burst release. Moreover, the above-mentioned encapsulation technology is only used for antibacterial purposes and does not involve yellowing inhibition.

[0005] Therefore, it is of great significance to develop a method that can delay postharvest yellowing of broccoli. Summary of the Invention

[0006] The purpose of this invention is to provide a microcapsule-based sustained-release fumigant of valerian oil and its application in delaying postharvest yellowing of broccoli, so as to solve the problems existing in the prior art. This invention provides a sustained-release fumigation system for highly volatile plant essential oils, which regulates the postharvest senescence process of cruciferous vegetable broccoli through the synergistic regulation of microcapsule encapsulation and fumigation process.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] One of the technical solutions of this invention is to provide a method for preparing a microcapsule-based sustained-release fumigant of valerian oil, comprising the following steps:

[0009] Sodium alginate solution, surfactant and valerian oil are mixed to form a primary emulsion, and the primary emulsion is homogenized to obtain sodium alginate-valerian oil emulsion;

[0010] The sodium alginate-valerian oil emulsion was added dropwise to a calcium chloride solution to obtain the microcapsule-based valerian oil sustained-release fumigant.

[0011] This invention uses calcium chloride as a cross-linking agent, which can rapidly form a stable "eggshell" structure with sodium alginate, and has advantages such as high solubility, fast cross-linking speed, and suitable pH. Compared with other calcium salts, calcium chloride can better retain the active ingredients of valerian oil while meeting food safety standards. Although alternatives such as strontium chloride may improve certain properties, calcium chloride remains the best choice considering cost, safety, and process stability.

[0012] Preferably, the sodium alginate solution has a mass fraction of 1-2%; the volume of Tween-80 is 4-6% of the volume of the sodium alginate solution; and the surfactant includes one or more of Tween-80, Tween-60, and PEG-40 hydrogenated castor oil.

[0013] Preferably, the homogenization includes homogenizing at a rotation speed of 11,000 to 13,000 rpm for 8 to 12 minutes in a homogenizer.

[0014] Preferably, the dropping rate of the sodium alginate-valerian oil emulsion is 2-4 mL / min.

[0015] Preferably, the calcium chloride solution has a mass fraction of 8-12%.

[0016] Preferably, the drug loading of the microcapsule-based valerian oil sustained-release fumigant is 34-36 wt%.

[0017] The second technical solution of the present invention provides a microcapsule-based sustained-release fumigant prepared by the above preparation method.

[0018] The third technical solution of the present invention provides the application of the above-mentioned microcapsule-based valerian oil sustained-release fumigant in delaying postharvest yellowing of broccoli.

[0019] Fourth technical solution of the present invention: A method for delaying postharvest yellowing of broccoli, comprising the following steps:

[0020] Broccoli and the microcapsule-based valerian oil sustained-release fumigant of claim 7 are mixed and then sealed for fumigation.

[0021] Preferably, the dosage of the microcapsule-based valerian oil sustained-release fumigant is 0.02–0.06 g / L air; the sealed fumigation includes: sealed fumigation for 72 hours in a dark environment at 19–21°C and 85% RH.

[0022] This invention innovates the microcapsule carrier structure, enabling sodium alginate and Ca... 2+Cross-linking forms microcapsules, solving the problem of higher evaporation rates and essential oil loss during 24-hour liquid fumigation. Furthermore, in a 15L fumigation space, the optimal dosage of the microcapsule-based sustained-release valerian oil fumigant described in this invention is 0.6g. Calculations based on a drug loading of 34-36wt% show an equivalent dosage of 0.2g, achieving a preservation effect similar to 0.4g of liquid valerian oil, significantly reducing the amount of essential oil used.

[0023] The release mechanism of the microcapsules described in this invention is as follows: initial rapid release stage (0-2h): surface adsorbed essential oils are rapidly released, quickly establishing an effective antibacterial concentration; intermediate stable release stage (2-24h): linear release is achieved by regulating the cross-linking density; late sustained release stage (24-72h): the microcapsule core is continuously released, maintaining an effective concentration up to 72h.

[0024] This invention utilizes humidity response characteristics (≥80%RH triggers swelling) to achieve a stable release of 75% of the active ingredients within 48 hours, completely avoiding the accumulation of odorous substances such as hexanal caused by the sudden release of >90% of the active ingredients within 2 hours of liquid fumigation.

[0025] The present invention discloses the following technical effects:

[0026] 1. Effectively inhibits post-harvest yellowing of broccoli: After treatment with the microcapsule-based valerian oil slow-release fumigant described in this invention, the shelf life of broccoli can be extended to 5 days. Broccoli without any treatment will yellow after 3 days. Moreover, the yellowing index of broccoli treated with the microcapsule-based valerian oil slow-release fumigant described in this invention after 5 days is significantly lower than that treated by direct fumigation with valerian oil.

[0027] 2. Improved economic benefits: The microcapsule loading capacity of the valerian oil sustained-release fumigant based on microcapsules described in this invention is significantly improved, reducing the amount of valerian oil used by 50%. Moreover, the valerian oil sustained-release fumigant based on microcapsules can extend the time for maintaining an effective concentration to 72 hours. Attached Figure Description

[0028] Figure 1 The values ​​of L*, a*, and b* of broccoli after treatment in Comparative Examples 1, 2 and 1 are given, where (a) is the L* value, (b) is the a* value, and (c) is the b* value.

[0029] Figure 2 This is a comparison of the effective substance volatilization rate between Comparative Example 2 and Example 1. Detailed Implementation

[0030] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0031] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0032] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0033] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0034] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0035] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0036] Unless otherwise specified, all raw materials used in the following embodiments and comparative examples of this invention are commercially available products, and the source of these commercially available products does not affect the technical effect of this invention.

[0037] Unless otherwise specified, the room temperature involved in this invention is 25±5℃.

[0038] In the following embodiments and comparative examples of this invention, the testing method for the L*, a*, and b* values ​​of the treated broccoli was as follows: The color parameters a*, b*, and L* on the surface of the broccoli florets were measured using a CR-400 colorimeter (Konica Minolta Sensing, Osaka, Japan). Three parts of each broccoli head were randomly selected and measured. Each measurement was repeated three times.

[0039] The decay rate is determined by the percentage of decayed samples out of the total sample size. The formula is: Decay rate = (Number of decayed samples / Total sample size) × 100%.

[0040] Effective substance contact time: The effective substance contact time is calculated from the time the fumigation substance is placed. The weight of the fumigation substance is measured every 12 hours until the mass of the fumigation substance remains unchanged.

[0041] Volatilization rate of active ingredient: Accurately weigh the dried microcapsules (or liquid essential oil) by mass m1 and place them in a weighing bottle. Weigh the microcapsules (or liquid essential oil) by mass m2 every 12 hours. When the mass of the microcapsules (or liquid essential oil) no longer changes, record the mass as m3. Volatilization rate of active ingredient = (m1-m2) / (m1-m3) × 100%.

[0042] Example 1

[0043] Step 1: Preparation of microcapsules

[0044] Sodium alginate was dissolved in water, and the solution was heated in a 60°C water bath for 3 hours until all sodium alginate was dissolved, thus preparing a 1.5 wt% sodium alginate solution. After cooling to room temperature, Tween-80 (the volume of Tween-80 was 5% of the volume of the sodium alginate solution) and valerian oil were added and stirred until fully dissolved. The solution was then homogenized at 12,000 rpm for 10 minutes to obtain an emulsion.

[0045] The obtained emulsion was added dropwise to 1000 mL of 10 wt% CaCl2 aqueous solution at a rate of 2-4 mL / min, stirred at 500 rpm for 30 min, and the microspheres were collected by centrifugation and dried in a cool and ventilated place for 24 h to obtain a sustained-release fumigant of valerian oil with a drug loading of 35 wt%.

[0046] Step 2: Broccoli preparation

[0047] Fresh broccoli (head diameter 12±2cm, free from disease, pests and mechanical damage) within 24 hours of harvest were selected and 5 replicates were set up.

[0048] The broccoli was sealed in a 0.03mm thick PE bag to form a 15L sealed space. Inside the bag, a petri dish was placed containing 0.6g of valerian oil slow-release fumigant with a drug loading of 35wt%.

[0049] Step 3: Fumigation and Storage

[0050] Fumigation conditions: Fumigate for 72 hours in a dark environment at 20±1℃ and 85%RH.

[0051] After fumigation, the products are transferred to a cold storage at 20°C and their commercial value is assessed daily by taking photos.

[0052] Example 2

[0053] Step 1: Preparation of microcapsules

[0054] Sodium alginate was dissolved in water, and the solution was heated in a 60°C water bath for 3 hours until all sodium alginate was dissolved, thus preparing a 1.5 wt% sodium alginate solution. After cooling to room temperature, Tween-80 (the volume of Tween-80 was 5% of the volume of the sodium alginate solution) and valerian oil were added and stirred until fully dissolved. The solution was then homogenized at 12,000 rpm for 10 minutes to obtain an emulsion.

[0055] The obtained emulsion was added dropwise to 1000 mL of 10 wt% CaCl2 aqueous solution at a rate of 2-4 mL / min, stirred at 500 rpm for 30 min, and the microspheres were collected by centrifugation and dried in a cool and ventilated place for 24 h to obtain a sustained-release fumigant of valerian oil with a drug loading of 35 wt%.

[0056] Step 2: Broccoli preparation

[0057] Fresh broccoli (head diameter 12±2cm, free from disease, pests and mechanical damage) within 24 hours of harvest were selected and 5 replicates were set up.

[0058] The broccoli was sealed in a 0.03mm thick PE bag to form a 15L sealed space. Inside the bag, a petri dish was placed containing 0.9g of valerian oil slow-release fumigant with a drug loading of 35wt%.

[0059] Step 3: Fumigation and Storage

[0060] Fumigation conditions: Fumigate for 72 hours in a dark environment at 20±1℃ and 85%RH.

[0061] After fumigation, the products are transferred to a cold storage at 20°C and their commercial value is assessed daily by taking photos.

[0062] Example 3

[0063] Step 1: Preparation of microcapsules

[0064] Sodium alginate was dissolved in water, and the solution was heated in a 60°C water bath for 3 hours until all sodium alginate was dissolved, thus preparing a 1.5 wt% sodium alginate solution. After cooling to room temperature, Tween-80 (the volume of Tween-80 was 5% of the volume of the sodium alginate solution) and valerian oil were added and stirred until fully dissolved. The solution was then homogenized at 12,000 rpm for 10 minutes to obtain an emulsion.

[0065] The obtained emulsion was added dropwise to 1000 mL of 10 wt% CaCl2 aqueous solution at a rate of 2-4 mL / min, stirred at 500 rpm for 30 min, and the microspheres were collected by centrifugation and dried in a cool and ventilated place for 24 h to obtain a sustained-release fumigant of valerian oil with a drug loading of 35 wt%.

[0066] Step 2: Broccoli preparation

[0067] Fresh broccoli (head diameter 12±2cm, free from disease, pests and mechanical damage) within 24 hours of harvest were selected and 5 replicates were set up.

[0068] The broccoli was sealed in a 0.03mm thick PE bag to form a 15L sealed space. Inside the bag, a petri dish was placed containing 0.3g of valerian oil slow-release fumigant with a drug loading of 35wt%.

[0069] Step 3: Fumigation and Storage

[0070] Fumigation conditions: Fumigate for 72 hours in a dark environment at 20±1℃ and 85%RH.

[0071] After fumigation, the products are transferred to a cold storage at 20°C and their commercial value is assessed daily by taking photos.

[0072] Comparative Example 1 (Blank Control Group)

[0073] Step 1: Broccoli preparation

[0074] Fresh broccoli (head diameter 12±2cm, free from disease, pests and mechanical damage) within 24 hours of harvest were selected and 5 replicates were set up.

[0075] Seal the broccoli in a 0.03mm thick PE bag.

[0076] Step 2: Fumigation and Storage

[0077] Fumigation conditions: Fumigate for 24 hours in a dark environment at 20±1℃ and 85%RH.

[0078] After fumigation, the products are transferred to a cold storage at 20°C and their commercial value is assessed daily by taking photos.

[0079] Comparative Example 2 (Fumigation directly using valerian oil)

[0080] Step 1: Broccoli preparation

[0081] Fresh broccoli (head diameter 12±2cm, free from disease, pests and mechanical damage) within 24 hours of harvest were selected and 5 replicates were set up.

[0082] The broccoli was sealed in a 0.03mm thick PE bag to form a 15L sealed space, and 400μL of valerian oil was placed in a petri dish inside.

[0083] Step 2: Fumigation and Storage

[0084] Fumigation conditions: Fumigate for 24 hours in a dark environment at 20±1℃ and 85%RH.

[0085] After fumigation, the products are transferred to a cold storage at 20°C and their commercial value is assessed daily by taking photos.

[0086] The results obtained from Examples 1-3 and Comparative Examples 1-2 are shown in Table 1.

[0087] Table 1

[0088]

[0089]

[0090] Figure 1 The values ​​of L*, a*, and b* of broccoli after treatment in Comparative Examples 1, 2 and 1 are given, where (a) is the L* value, (b) is the a* value, and (c) is the b* value. Figure 1 In the various graphs, the different letters 'a' and 'b' represent significant differences between the data.

[0091] Figure 2 This is a comparison of the effective substance volatilization rate between Comparative Example 2 and Example 1.

[0092] exist Figure 1 and Figure 2 In the text, CK refers to Comparative Example 1, liquid fumigation refers to Comparative Example 2, and embedding fumigation refers to Example 1.

[0093] From Table 1, Figure 1 and Figure 2 It can be seen that microencapsulation sustained-release technology significantly improves the preservation effect and utilization efficiency of valerian oil fumigation. Example 1 uses microencapsulation with a drug loading of 35 wt%, and its high encapsulation rate of 36.2% indicates that valerian oil is effectively embedded in sodium alginate microspheres, and the process stability is good. In terms of preservation performance, the L value of Example 1 (39.55333±1.1999) is significantly lower than that of Comparative Example 1 (44.12111±1.3893), indicating that microencapsulation treatment effectively inhibits browning; the a value (-9.08556±0.62505) is closer to the neutral axis, proving that chlorophyll degradation is slower; the b value (11.76667±1.31607) is significantly lower than that of Comparative Example 1 (17.55556±1.68816), indicating that the yellowing process is delayed. More importantly, Example 1 maintained zero decay rate during the 72-hour test period, far exceeding Comparative Example 2 (24-hour effective period) and Comparative Example 1 (1 / 6 decay rate) of direct liquid fumigation. The "lower" odor index further illustrates that microencapsulation sustained-release technology overcomes the shortcomings of traditional fumigation methods, such as high volatility and strong irritating odor. The comparative experiments clearly show that Comparative Example 1, which did not use microencapsulation technology, performed poorly in all indicators, while Comparative Example 2, although showing no decay, had a short effective time and a noticeable odor. This verifies the necessity of sustained-release carriers in prolonging efficacy and ensuring stable release.

[0094] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0095] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a microcapsule-based sustained-release valerian oil fumigant, characterized in that, Includes the following steps: Sodium alginate solution, surfactant and valerian oil are mixed to form a primary emulsion, and the primary emulsion is homogenized to obtain sodium alginate-valerian oil emulsion; The sodium alginate-valerian oil emulsion was added dropwise to a calcium chloride solution to obtain the microcapsule-based valerian oil sustained-release fumigant.

2. The preparation method according to claim 1, characterized in that, The sodium alginate solution has a mass fraction of 1-2%; and / or, the volume of Tween-80 is 4-6% of the volume of the sodium alginate solution; and / or, the surfactant includes one or more of Tween-80, Tween-60, and PEG-40 hydrogenated castor oil.

3. The preparation method according to claim 1, characterized in that, The homogenization includes homogenizing in a homogenizer at a rotation speed of 11,000 to 13,000 rpm for 8 to 12 minutes.

4. The preparation method according to claim 1, characterized in that, The sodium alginate-valerian oil emulsion was added at a rate of 2–4 mL / min.

5. The preparation method according to claim 1, characterized in that, The calcium chloride solution has a mass fraction of 8-12%.

6. The preparation method according to claim 1, characterized in that, The drug loading of the microcapsule-based valerian oil sustained-release fumigant is 34–36 wt%.

7. The valerian oil sustained-release fumigant based on microcapsules prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the microcapsule-based valerian oil sustained-release fumigant of claim 7 in delaying postharvest yellowing of broccoli.

9. A method for delaying postharvest yellowing of broccoli, characterized in that, Includes the following steps: Broccoli and the microcapsule-based valerian oil sustained-release fumigant of claim 7 are mixed and then sealed for fumigation.

10. The method according to claim 9, characterized in that, The dosage of the microcapsule-based valerian oil sustained-release fumigant is 0.02–0.06 g / L air; and / or, the sealed fumigation includes: sealed fumigation for 72 hours in a dark environment at 19–21°C and 85% RH.

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