Preservative suitable for green fruits and vegetables and preparation method and application thereof

Abstract

The invention belongs to the technical field of fruit and vegetable fresh-keeping, and provides a fresh-keeping agent suitable for green fruits and vegetables and a preparation method and application of the fresh-keeping agent in order to solve the problem that a green-keeping method and the optimal fresh-keeping color of fresh-cut broccoli are not clear in the prior art. The film-forming agent is composed of chitosan and konjaku flour, and the active components comprise a gardenia extract and tea polyphenol. The fresh-keeping agent belongs to food pigment and biological fresh-keeping agents, is safe, excellent, green and environment-friendly, and when the method provided by the invention is used for inhibiting and controlling the yellowing of the fresh-cut broccoli, the yellowing degree of the fresh-cut broccoli can be obviously controlled, the rising of the yellowing rate and the yellowing index of the fresh-cut broccoli can be effectively inhibited, and relatively good sensory quality can be maintained. Moreover, all the raw materials used in the preservative are easy to obtain, and the preservative belongs to food pigments and biological preservatives, is safe, excellent, green and environment-friendly, is simple in preparation method, and is beneficial to popularization and application of actual production.

Description

Technical Field

[0001] The invention belongs to the technical field of fruit and vegetable preservation, and in particular relates to a preservative suitable for green fruits and vegetables, and a preparation method and application thereof. Background Art

[0002] Broccoli is a variant of the Brassica oleracea species in the Cruciferae family, with green flower heads as the product. It contains the anti-cancer substance glucosyl isothiocyanate, which can prevent the growth of early cancer cells and has special health benefits.

[0003] However, there are many thorny problems in the preservation of broccoli. First, broccoli is prone to yellowing. After picking, the chlorophyll inside it will quickly decompose, causing the color of the broccoli to change from emerald green to yellow-green, greatly affecting the appearance quality, and consumers' willingness to buy will also decrease. Secondly, during the preservation period, the nutrients of broccoli are lost at a fast rate. For example, the content of antioxidants such as vitamin C and flavonoids continues to decline, and the nutritional value is greatly reduced. Furthermore, the problem of microbial growth is serious. The surface of broccoli is easily contaminated by bacteria, mold, etc. Under suitable temperature and humidity conditions, microorganisms multiply in large numbers, causing broccoli to rot, mildew, etc., shortening the shelf life. In addition, traditional preservation methods have limited effects. Although refrigeration can delay deterioration to a certain extent, it will make the taste of broccoli worse, and ordinary packaging cannot effectively prevent water loss and gas exchange, making it difficult to maintain the freshness of broccoli.

[0004] At the same time, in terms of the preservation of fresh-cut broccoli, researchers have been committed to exploring effective preservatives to delay its yellowing in recent years. At present, there are certain disadvantages in the existing sources of film-forming agents and the use of chemical agents. With the growing demand of consumers for food safety, natural, environmentally friendly and non-toxic preservatives have become an inevitable trend in future food applications. Chitosan, as a film-forming agent from natural sources, has good application prospects. However, the preservation effect of film-forming agents on fresh-cut broccoli is limited, and it is still necessary to further find effective exogenous treatment methods to maintain the quality of fresh-cut broccoli.

[0005] In summary, the development of a preservation technology based on chitosan combined with effective exogenous treatment is of great significance for the preservation of green fruits and vegetables including fresh-cut broccoli. It can not only meet the market demand for food safety, but also fill the shortcomings of existing preservation technology and has broad market application prospects. Summary of the invention

[0006] In order to overcome the problems of the prior art, the present invention proposes a preservative suitable for green fruits and vegetables, and a preparation method and application thereof. The preservative further adds natural active ingredients on the basis of antibacterial properties, and under the synergistic effect of various components, it effectively inhibits the yellowing of green fruits and vegetables and prolongs the shelf life.

[0007] The prior art uses a composite coating of chitosan and melatonin to preserve fresh-cut broccoli. Through sensory evaluation, physiological and biochemical index determination, and texture analysis, the quality of fresh-cut broccoli and chlorophyll metabolism in each treatment group during storage are studied. Studies have shown that the composite treatment of CTS and MT can delay the yellowing of broccoli to a certain extent and maintain its quality. However, the preservation effect achieved by using chitosan as a single film-forming component is limited. Some people may irritate the gastrointestinal mucosa after taking melatonin, causing gastrointestinal discomfort symptoms, and melatonin has a certain dependence. Long-term intake will cause changes in hormone levels in the body. Therefore, the inventor has studied this, using chitosan as a film-forming component, adding tea polyphenols and gardenia extracts for compounding, which can play a good antioxidant, fresh-keeping and color-protecting role. Based on this, further research and discussion found that the addition of konjac powder in the film-forming agent can form an antibacterial film, play a barrier role, delay the entry of external oxygen into the interior of fruits and vegetables, and at the same time, as a carrier of preservative inhibitors, it is beneficial to maintain the post-harvest quality of fruits and vegetables and extend the shelf life. In view of this, the inventor provides the following solution of the present invention.

[0008] In order to achieve the above object, the first aspect of the present invention provides a preservative suitable for green fruits and vegetables, wherein the raw materials of the preservative include a film-forming agent and an active component, wherein the film-forming agent is composed of chitosan and konjac flour, and the active component includes a gardenia extract and tea polyphenols, and the weight proportion of each raw material is:

[0009]

[0010] Further preferably, the weight ratio of each raw material is:

[0011]

[0012] Furthermore, the fruits and vegetables include broccoli, green peppers, cucumbers, peas, and cherry tomatoes.

[0013] The second aspect of the present invention provides a method for preparing the preservative according to the first aspect, comprising the following steps:

[0014] (1) Preparation of film-forming agent: a certain amount of chitosan and konjac flour are weighed according to the above weight fraction ratio, chitosan film-forming solution is prepared with acetic acid solution as solvent, and konjac flour is dissolved with distilled water to obtain konjac flour solution; the chitosan film-forming solution and konjac flour solution are filtered to remove impurities, and then the two are mixed to obtain a film-forming agent solution;

[0015] (2) Preparation of preservative: Weigh a certain amount of gardenia extract and tea polyphenols according to the above weight fraction ratio; heat the film-forming agent solution prepared in step (1) in a water bath, add gardenia extract and tea polyphenols thereto, stir, and remove bubbles by ultrasound, thereby obtaining the preservative suitable for green fruits and vegetables.

[0016] Furthermore, in step (1), when preparing the konjac flour solution, a magnetic stirrer is used to stir for 0.5 to 2 hours to prevent the formation of gel and ensure that the solution is uniform.

[0017] Furthermore, in step (2), the water bath heating temperature is 45°C to 55°C, and the gardenia extract and tea polyphenols are added to the film-forming agent solution, stirred for 5 to 15 minutes, and ultrasonically treated for 10 to 20 minutes.

[0018] The third aspect of the present invention provides the use of the preservative described in the first aspect in preserving green fruits and vegetables.

[0019] Furthermore, the fruits and vegetables include broccoli, green peppers, cucumbers, peas, and cherry tomatoes.

[0020] Furthermore, the green fruits and vegetables are preserved by soaking or spraying.

[0021] Furthermore, the soaking method comprises the following steps: cutting green fruits and vegetables into small pieces, soaking them in the preservative for 3-10 minutes, taking them out and drying them naturally, putting them into food-grade fresh-keeping bags, and refrigerating them in a 4°C refrigerator.

[0022] The advantages and beneficial effects of the present invention are:

[0023] 1. The preservative of the present invention is added with active components composed of tea polyphenols and gardenia extract, wherein the gardenia extract (gardenia green) is a natural pigment made by fine processing with gardenia blue pigment as raw material, and its main components are carotene crocin and crocetin; tea polyphenols are the functional active substances with the highest content in tea leaves, which are widely used in the fields of food, medicine, etc., can improve the quality of food, enhance the antibacterial and antioxidant effects of compound additives, and have great development potential as natural food additives. In the compound system, tea polyphenols and gardenia extract are both colored powders, and the two synergistically play the role of anti-oxidation, fresh-keeping and color protection, significantly control the yellowing degree of fresh-cut broccoli, effectively inhibit the increase of its yellowing rate and yellowing index, and can maintain good sensory quality.

[0024] 2. The preservative of the present invention uses chitosan and konjac flour blended film as film-forming agents, wherein chitosan has excellent film-forming property and antibacterial effect, while konjac glucan has good synergistic effect, compatibility and film-forming properties, and the combination of the two has good compatibility and synergistic effect.

[0025] 3. All raw materials used in the preservative of the present invention are easily available, belonging to the category of food pigments and biological preservatives, which are safe, excellent, green and environmentally friendly, and have a simple preparation method, which is conducive to the promotion and application of actual production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0027] Figure 1 Shows the changes in the yellowing index of broccoli after being treated with different groups of preservatives;

[0028] Figure 2 Shows the changes in the yellowing rate of broccoli after being treated with different groups of preservatives. DETAILED DESCRIPTION

[0029] The implementation of the present invention is not limited to the following embodiments, and any form of modification and / or change made to the present invention will fall within the scope of protection of the present invention. In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. Unless otherwise specified, the methods used in the embodiments are common techniques in the art.

[0030] For numerical ranges, the endpoints of each range, the endpoints of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be deemed to be specifically disclosed herein.

[0031] The main raw materials used in the following examples are shown in Table 1.

[0032] Table 1 Main raw materials

[0033]

[0034] Embodiment 1:

[0035] This embodiment provides a preservative suitable for green fruits and vegetables. The raw materials of the preservative include a film-forming agent and an active component. The film-forming agent is composed of chitosan and konjac flour, and the active component includes gardenia extract and tea polyphenols.

[0036] The preparation method of the preservative comprises the following steps:

[0037] (1) Preparation of film-forming agent: Weigh a certain amount of chitosan, and prepare chitosan film-forming solution with 1% acetic acid solution as solvent; weigh a certain amount of konjac flour, and dissolve the konjac flour with distilled water, stirring continuously to prevent gel formation, and stirring with a magnetic stirrer for 1 hour to ensure that the solution is uniform, thereby obtaining a konjac flour solution; filter the chitosan film-forming solution and the konjac flour solution to remove impurities, and then mix the two to obtain a film-forming agent solution, wherein the film-forming agent solution is a composite solution of 0.6% chitosan and 0.3% konjac flour (w / v).

[0038] (2) Preparation of preservative: Weigh a certain amount of gardenia extract and tea polyphenols, heat the film-forming agent solution prepared in step (1) in a water bath, add 0.03% gardenia extract (w / v) and 0.6% tea polyphenols (w / v) thereto, stir for 10 min, and perform ultrasonic treatment for 15 min to remove bubbles, thereby obtaining the preservative suitable for green fruits and vegetables (0.6% CTS + 0.3% KJ + 0.6% TP + 0.03% ZG).

[0039] Tea polyphenols and gardenia extracts are both colored powders. Studies have found that excessive tea polyphenols and gardenia extracts cannot be well dissolved in the film-forming agent solution. If they clump or are not completely dissolved, they are not conducive to their function. The amount of tea polyphenols and gardenia extracts provided in this application can ensure that both are well dissolved in the film-forming agent solution and can play the best antioxidant, freshness-preserving and color-protecting role.

[0040] Comparative Example 1:

[0041] This comparative example provides a preservative, which is different from the preservative in Example 1 in that konjac flour is not added, and the preparation method is as follows:

[0042] (1) Weigh a certain amount of chitosan, use 1% acetic acid solution as solvent to prepare chitosan film-forming solution, filter the chitosan film-forming solution to remove impurities, and the chitosan concentration in the solution is 0.5% (w / v).

[0043] (2) Preparation of preservative: Weigh a certain amount of gardenia extract and tea polyphenols, heat the chitosan film-forming solution prepared in step (1) in a water bath, add 0.05% gardenia extract (w / v) and 0.5% tea polyphenols (w / v) thereto, stir for 10 min, and remove bubbles by ultrasonication for 15 min, thereby obtaining a preservative (0.5% CTS + 0.5% TP + 0.05% ZG).

[0044] Comparative Example 2:

[0045] This comparative example provides a preservative, which differs from the preservative in Example 1 in that tea polyphenols are not added, and the preparation method is as follows:

[0046] (1) Preparation of film-forming agent: Weigh a certain amount of chitosan, and prepare chitosan film-forming solution with 1% acetic acid solution as solvent; weigh a certain amount of konjac flour, and dissolve the konjac flour with distilled water, stirring continuously to prevent gel formation, and stirring with a magnetic stirrer for 1 hour to ensure that the solution is uniform, thereby obtaining a konjac flour solution; filter the chitosan film-forming solution and the konjac flour solution to remove impurities, and then mix the two to obtain a film-forming agent solution, wherein the film-forming agent solution is a composite solution of 0.6% chitosan and 0.3% konjac flour (w / v).

[0047] (2) Preparation of preservative: Weigh a certain amount of gardenia extract, heat the chitosan film-forming solution prepared in step (1) in a water bath, add 0.05% gardenia extract (w / v) thereto, stir for 10 min, and remove bubbles by ultrasonication for 15 min, thereby obtaining a preservative (0.6% CTS + 0.3% KJ + 0.05% ZG).

[0048] Comparative Example 3:

[0049] This comparative example provides a preservative, which is different from the preservative in Example 1 in that no gardenia extract is added, and the preparation method is as follows:

[0050] (1) Preparation of film-forming agent: Weigh a certain amount of chitosan, and prepare chitosan film-forming solution with 1% acetic acid solution as solvent; weigh a certain amount of konjac flour, and dissolve the konjac flour with distilled water, stirring continuously to prevent gel formation, and stirring with a magnetic stirrer for 1 hour to ensure that the solution is uniform, thereby obtaining a konjac flour solution; filter the chitosan film-forming solution and the konjac flour solution to remove impurities, and then mix the two to obtain a film-forming agent solution, wherein the film-forming agent solution is a composite solution of 0.6% chitosan and 0.3% konjac flour (w / v).

[0051] (2) Preparation of preservative: Weigh a certain amount of tea polyphenols, heat the film-forming agent solution prepared in step (1) in a water bath, add 1% tea polyphenols (w / v) thereto, stir for 10 min, and remove bubbles by ultrasonication for 15 min, thereby obtaining a preservative (0.6% CTS + 0.3% KJ + 1% TP).

[0052] Test Case

[0053] In order to explore the preservation effect of preservatives with different components, this test example takes broccoli as an example, and uses the preservatives prepared in the above embodiments and comparative examples to perform preservation treatment. The specific method is as follows:

[0054] Select the broccoli of uniform size, free of mechanical damage and pests and diseases from the harvested broccoli, and cut them into small florets with a floret diameter of about 3 cm and a rhizome length of about 2 cm. Rinse them, dry them naturally and set aside.

[0055] The fresh-cut florets were soaked in the preservatives prepared in the above embodiments and comparative examples for 5 minutes, naturally dried, and then packed into polyethylene food-grade fresh-keeping bags, each bag containing 300 g of fresh-cut broccoli, and stored in a refrigerator at 4°C.

[0056] The appearance of broccoli was evaluated by observing the yellowing area on the surface of the curd and referring to the method of Fang et al. (FANG HX, LUO F, LIP X, et al. Potential of jasmonic acid (JA) in accelerating postharvest yellowing of broccoli by promoting its chlorophyll degradation[J]. Food Chemistry, 2020, 309: 125737. DOI: 10.1016 / j.foodchem.2019.125737.). The grading standard for yellowing is: Grade 0: the flower curd is dark green with no yellowing; Grade 1: the flower curd is dark green and uniform in color (with only a few yellowing buds); Grade 2: the flower curd is light green, the buds are slightly yellow, and the yellowing area of ​​the buds is 25% to 50%; Grade 3: the flower curd is yellow-green, most of the buds fade from green to yellow, and the yellowing area of ​​the buds is 50% to 75%; Grade 4: the flower curd is obviously yellow, the overall color is yellow, and the yellowing area of ​​the buds is greater than 75%.

[0057] The yellowing index results are calculated according to the following formula:

[0058] Yellowing index (%) = Σ[(yellowing level) × (number of broccoli of this level)] / [(maximum yellowing level × (total number of broccoli)] × 100%

[0059] The yellowing rate is evaluated according to the following formula:

[0060] Yellowing rate (%) = (number of yellowed broccoli / total number of broccoli) × 100%

[0061] Here, "yellowing" refers to the buds with obvious yellowing on the surface of the flower curd (Volden, J., Bengtsson, GB, & Wicklund, T. (2009). Glucosinolates, l-ascorbic acid, total phenols, anthocyanins, antioxidant capacities and colour in cauliflower (Brassica oleracea L.ssp.botrytis); effects of long-term freezer storage. Food Chemistry, 112, 967–976. DOI: 10.1016 / j.foodchem.2008.07.018.).

[0062] like Figure 1 , Figure 2 As shown, adding gardenia extract (Comparative Example 1) to chitosan and tea polyphenols in equal proportions can delay the yellowing of fresh-cut broccoli, and when chitosan and konjac gum are prepared in a 2:1 ratio, it can be observed that the overall greening effect of adding the active ingredient gardenia extract (Comparative Example 2) is better than that of tea polyphenols (Comparative Example 3). Based on the previous screening of the optimal concentrations of film-forming agents and preservatives, it was finally found that compared with the blank control CK and Comparative Examples 1-3, the preservative prepared in Example 1 can significantly control the yellowing degree of fresh-cut broccoli and effectively inhibit the increase of its yellowing index and yellowing rate.

[0063] Finally, it should be noted that the above is only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred arrangement scheme, a person skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A preservative suitable for green fruits and vegetables, characterized in that: The raw materials of the preservative include a film-forming agent and an active component, wherein the film-forming agent is composed of chitosan and konjac flour, and the active component includes gardenia extract and tea polyphenols, and the weight proportion of each raw material is:

2. The preservative for green fruits and vegetables according to claim 1, characterized in that: The weight ratio of each raw material is:

3. The preservative suitable for green fruits and vegetables according to claim 1 or 2, characterized in that: The fruits and vegetables include broccoli, green peppers, cucumbers, peas, and cherry tomatoes.

4. A method for preparing a preservative suitable for green fruits and vegetables as claimed in any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: (1) Preparation of film-forming agent: according to the weight fraction ratio of claim 1 or 2, a certain amount of chitosan and konjac flour are weighed respectively, chitosan film-forming solution is prepared with acetic acid solution as solvent, and konjac flour is dissolved with distilled water to obtain konjac flour solution; the chitosan film-forming solution and konjac flour solution are filtered to remove impurities respectively, and then the two are mixed to obtain a film-forming agent solution; (2) Preparation of the preservative: Weigh a certain amount of gardenia extract and tea polyphenols according to the weight fraction ratio of claim 1 or 2; heat the film-forming agent solution prepared in step (1) in a water bath, add gardenia extract and tea polyphenols thereto, stir, and remove bubbles by ultrasound, thereby obtaining the preservative suitable for green fruits and vegetables.

5. The preparation method according to claim 4, characterized in that: In step (1), when preparing the konjac flour solution, stir it with a magnetic stirrer for 0.5 to 2 hours.

6. The preparation method according to claim 4, characterized in that: In step (2), the water bath heating temperature is 45° C. to 55° C., and the gardenia extract and tea polyphenols are added to the film-forming agent solution, stirred for 5 to 15 minutes, and ultrasonically treated for 10 to 20 minutes.

7. Use of the preservative according to any one of claims 1 to 3 in preserving green fruits and vegetables.

8. The use according to claim 7, characterized in that: The fruits and vegetables include broccoli, green peppers, cucumbers, peas, and cherry tomatoes.

9. The use according to claim 7 or 8, characterized in that: The green fruits and vegetables are preserved by soaking or spraying.

10. The use according to claim 9, characterized in that: The soaking method comprises the following steps: cutting green fruits and vegetables into small pieces, soaking them in the preservative for 3-10 minutes, taking them out and drying them naturally, putting them into food-grade fresh-keeping bags, and refrigerating them in a refrigerator at 4°C.

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