阅读说明：本技术 一种木樨草素鸡皮明胶可食性保鲜液、保鲜膜、制备方法和应用 (Edible trifoliol vegetable chicken skin gelatin preservative solution, preservative film, preparation method and application ) 是由 孙静 申杰 潘爱銮 杜金平 皮劲松 李新 李开耀 于 2020-12-15 设计创作，主要内容包括：本发明公开了一种木樨草素鸡皮明胶可食性保鲜液、保鲜膜、制备方法和应用,该保鲜液包括鸡皮明胶、壳聚糖、多元醇增塑剂、鸡皮油、木樨草素、转谷氨酰胺酶和水。保鲜膜通过保鲜液直接制备得到。保鲜液制备步骤为：鸡皮通过脱脂后再依次经过碱液处理和碱性蛋白酶溶液处理得到鸡皮明胶,从制备鸡皮明胶过程中的含脂肪溶液中提取得到鸡皮油；将鸡皮明胶、壳聚糖、多元醇增塑剂、鸡皮油、木樨草素混合后加入转谷氨酰胺酶进行催化交联,即得可食性保鲜液。该保鲜液成膜速度快,保鲜膜力学性能和阻隔能力强,同时具有良好的抑菌和抗氧化作用,制备过程操作简单,成本低,应用方式灵活多样,即可浸泡或喷淋后成膜保鲜,又可成膜后包装保鲜,应用广泛。(The invention discloses edible preservative solution for luteolin chicken skin gelatin, a preservative film, a preparation method and application. The preservative film is directly prepared from preservative solution. The preparation method of the fresh-keeping liquid comprises the following steps: degreasing chicken skin, sequentially treating the chicken skin with alkali liquor and alkaline protease to obtain chicken skin gelatin, and extracting fat-containing solution in the process of preparing the chicken skin gelatin to obtain chicken skin oil; mixing chicken skin gelatin, chitosan, polyol plasticizer, chicken skin oil and luteolin, adding transglutaminase, and catalytically crosslinking to obtain edible fresh-keeping solution. The preservative solution has the advantages of high film forming speed, strong mechanical property and barrier capability of the preservative film, good antibacterial and antioxidant effects, simple preparation process operation, low cost, flexible and various application modes, capability of being soaked or sprayed for film forming preservation, capability of being packaged for preservation after being formed into a film, and wide application.)

1. The edible luteolin chicken skin gelatin fresh-keeping liquid is characterized by comprising the following components in parts by weight: 4-6 parts of chicken skin gelatin, 0.6-0.9 part of chitosan, 0.98-1.32 parts of polyol plasticizer, 0.49-1.98 parts of chicken skin oil, 0.098-0.147 part of luteolin, 0.0196-0.0528 parts of transglutaminase and 93.4-95.1 parts of water.

2. The preservative solution according to claim 1, wherein the chicken skin gelatin is obtained by degreasing chicken skin and then sequentially performing alkali solution treatment and alkaline protease solution treatment.

3. The preservative solution according to claim 2, wherein the alkaline protease is APG1115 protease or a serine protease.

4. A preservative film obtained by using the edible preservative solution of luteolin chicken skin gelatin as described in any one of claims 1 to 3.

5. A method of producing trifoliol egg skin gelatin edible preservative solution as claimed in any one of claims 1 to 3, comprising the steps of:

1) degreasing chicken skin by using ether to obtain degreased chicken skin and a fat-containing solution A1, sequentially treating the degreased chicken skin by using an alkali liquor and an alkaline protease solution, and extracting gelatin to obtain a gelatin crude extract; layering the obtained crude gelatin extractive solution to obtain upper layer containing fat solution A2, mixing with fat solution A1 to obtain lower layer containing gelatin solution, concentrating the gelatin solution, removing water, and vacuum freeze drying to obtain chicken skin gelatin;

2) adding water into the chicken skin gelatin obtained in the step 1) to prepare a chicken skin gelatin solution, mixing the chicken skin gelatin solution with the chitosan solution, adding a polyol plasticizer, and uniformly stirring to obtain a gelatin-chitosan-polyol plasticizer mixed solution;

3) extracting the chicken skin oil from the fat-containing solution A obtained in the step 1);

4) adding the chicken skin oil and luteolin obtained in the step 3) into the gelatin-chitosan-polyol plasticizer mixed solution obtained in the step 2), and stirring until the mixture is dissolved uniformly to obtain a mixed solution;

5) adjusting the pH of the mixed solution obtained in the step 5) to 5.8-6.1 by using alkali, then adding a certain amount of transglutaminase for catalytic crosslinking, heating to boil and deactivate the enzyme after the reaction is finished, cooling to room temperature, and then carrying out vacuum pressure reduction and deaeration to obtain the luteolin chicken skin gelatin edible fresh-keeping solution.

6. The preparation method according to claim 5, wherein in the step 1), the defatted chicken skin is sequentially treated by alkali liquor treatment and alkaline protease solution treatment to extract gelatin to obtain a crude gelatin extract, and the method comprises the following specific steps:

adding NaOH solution into the degreased chicken skin, and changing the solution at 38-50 ℃ every 6-8h for 2-3 times; heating for 0.5-2h at 40-60 ℃, centrifuging to obtain a protein phase, stirring the obtained protein phase for 20-30h, pulping, centrifuging, adding an alkaline protease solution and distilled water, carrying out water bath gel extraction, extracting for 30-40min at 40-60 ℃, and filtering to obtain a crude gelatin extracting solution, wherein the concentration of the NaOH solution is 0.04-0.06mol/L, and the mass-to-volume ratio of the degreased chicken skin to the NaOH solution is 1: 5.5-7 (g/mL); the concentration of the alkaline protease solution is 0.8-1.2mg/mL, and the mass volume of the protein phase and the protease solution is 1:1.8-2.5 (g/mL).

7. The production method according to claim 5,

in the step 3), the concrete steps are as follows:

placing the fat-containing solution A in a high-pressure extraction tank, and stirring at 45-50 deg.C for 10-20min to completely evaporate diethyl ether; then adding water, starting a circulating pump to circulate the fat solution at 80-98 ℃, heating to 98 ℃, closing an exhaust valve, heating for 3-5h under the conditions of 105-115 ℃ to obtain a mixture of water and the chicken skin oil, filtering, standing for 2-4h, and separating oil from water to obtain crude chicken oil; separating the crude chicken oil by a tubular separator to obtain chicken skin oil with the water content less than 0.1%;

in the step 5), the catalytic crosslinking conditions are as follows: stirring at 48-55 deg.C for 35-50 min.

8. The preparation method according to claim 5, wherein in the step 1), the mass ratio of the chicken skin gelatin to the chitosan to the polyol plasticizer is (4-6): (0.6-0.9): (0.98-1.32); in the step 4), the mass ratio of the chicken skin gelatin to the chicken skin oil to the luteolin is (4-6): 0.49-1.98: (0.098-0.147); in the step 5), the mass ratio of the chicken skin gelatin to the transglutaminase is (4-6): (0.0196-0.0528); the mass ratio of the water content in the chicken skin gelatin and the obtained edible fresh-keeping liquid is (4-6): (93.4-95.1).

9. The application of edible trifoliol egg skin gelatin preservative solution as claimed in any one of claims 1 to 3, wherein a product to be preserved is soaked in the preservative solution and taken out to form a film for preservation, or the preservative solution is sprayed on the surface of the product to be preserved to form a film for preservation.

10. The application of the luteolin chicken skin gelatin edible preservative film as claimed in claim 4, wherein the preservative film is packaged to keep fresh of a product to be preserved.

Technical Field

The invention relates to the field of food preservation, in particular to edible Daghestan Sweetclover vegetable chicken skin gelatin preservative solution, preservative film, a preparation method and application.

Background

Traditional organic combined package can produce poisonous and harmful substance and harm health under high temperature heating environment to and difficult decomposition causes the influence to the environment, and the urgent need is a novel packaging material to carry out partial substitution. Gelatin, as an animal protein, is widely used in the fields of food, photography, medicine, photosensitive material industry, and the like, due to its functional properties such as good water retention, film-forming property, emulsifying property, foaming property, and gelling property. Traditional gelatin is mainly derived from bones and skins of mammals (pigs and cattle), and is limited by the influence of epidemic diseases of animals in recent years. The fish gelatin has insufficient gel strength and thermal stability, and the product is difficult to utilize due to the dispersion.

The chicken is nearly 1350 million tons in China per year, the chicken skin is taken as a byproduct, the price is low, the acquisition is easy, the protein content is high, the chicken skin contains about 3 percent of collagen components, including three quarters of type I collagen and 15 percent of type II collagen, the chicken skin raw material has no abnormal odor and light color, and the decoloration is not needed in the process of processing the chicken skin into gelatin. The increasingly perfect mechanical processing degree of the broiler chickens lays a good foundation for providing raw materials with good and stable quality. The chicken skin is used as a source material for extracting gelatin, has better gel property and fluidity than pigskin and cowskin, and has lower water vapor transmission rate (WVP) and stronger mechanical property than aquatic gelatin film.

Therefore, the development and utilization of poultry resources to produce gelatin can not only make full use of resources, change waste into valuable, reduce environmental pollution and solve the problem of comprehensive utilization of poultry processing resources, but also enlarge the source of gelatin raw materials and the diversity of gelatin products, which undoubtedly has great social benefit and economic value.

Disclosure of Invention

The invention aims to provide edible trifoliol egg white gelatin preservative solution, preservative film, a preparation method and application. The preservative solution has the advantages of high film forming speed, strong mechanical property and barrier capability of the preservative film, good antibacterial and antioxidant effects, simple preparation process operation, low cost and flexible and various application modes, can be soaked or sprayed for film forming preservation, and can be packaged for preservation after being formed into a film; the specific application scenes comprise short-time temporary storage before sale or processing of eggs or duck eggs, fresh keeping of preserved egg and salted egg packaging, fruit packaging and the like, and the method has wide application prospect.

In order to solve the technical problems, the invention provides the following technical scheme:

the edible luteolin chicken skin gelatin fresh-keeping liquid comprises the following components in parts by weight:

4-6 parts of chicken skin gelatin, 0.6-0.9 part of chitosan, 0.98-1.32 parts of polyol plasticizer, 0.49-1.98 parts of chicken skin oil, 0.098-0.147 part of luteolin, 0.0196-0.0528 parts of transglutaminase (TGase) and 93.4-95.1 parts of water.

According to the scheme, the polyalcohol plasticizer is one or more of sorbitol, polyethylene glycol 200 or polyethylene glycol 400.

According to the scheme, the chicken skin gelatin is obtained by degreasing chicken skin and then sequentially treating the chicken skin with alkali liquor and alkaline protease solution. Preferably, the alkaline protease is an APG1115 protease or a class of serine proteases.

Provides a preservative film obtained by the edible preservative solution of luteolin chicken skin gelatin. The method specifically comprises the following steps: uniformly coating the fresh-keeping liquid on a horizontal clean polyvinyl chloride plate with edges, carrying out tape casting to form a film, washing the film with deionized water until the film is nearly neutral, and naturally drying the film at room temperature or air-drying the film by a blower.

The preparation method of the edible trifoliol vegetable chicken skin gelatin fresh-keeping liquid comprises the following steps:

1) degreasing chicken skin by using ether to obtain degreased chicken skin and a fat-containing solution A1, sequentially treating the degreased chicken skin by using an alkali liquor and an alkaline protease solution, and extracting gelatin to obtain a gelatin crude extract; layering the obtained crude gelatin extractive solution to obtain upper layer containing fat solution A2, mixing with fat solution A1 to obtain lower layer containing gelatin solution, concentrating the gelatin solution, removing water, and vacuum freeze drying to obtain chicken skin gelatin;

2) adding water into the chicken skin gelatin obtained in the step 1) to prepare a chicken skin gelatin solution, mixing the chicken skin gelatin solution with the chitosan solution, adding a polyol plasticizer, and uniformly stirring to obtain a gelatin-chitosan-polyol plasticizer mixed solution;

3) extracting the chicken skin oil from the fat-containing solution A obtained in the step 1);

4) adding the chicken skin oil and luteolin obtained in the step 3) into the gelatin-chitosan-polyol plasticizer mixed solution obtained in the step 2), and stirring until the mixture is dissolved uniformly to obtain a mixed solution;

5) adjusting the pH of the mixed solution obtained in the step 5) to 5.8-6.1 by using alkali, then adding a certain amount of TGase for catalytic crosslinking, heating to boil and deactivate the enzyme after the reaction is finished, cooling to room temperature, and then carrying out vacuum pressure reduction and deaeration to obtain the edible preservative solution of luteolin chicken skin gelatin.

According to the scheme, in the step 1), the method for degreasing the chicken skin by using the diethyl ether comprises the following specific steps: mincing chicken skin, adding water to absorb water to swell and dissolve for 10-20min, and then mixing the chicken skin and diethyl ether according to the mass volume ratio of 1: adding ether solution into the mixture at a concentration of 1.8-3g/mL, and standing at 4-10 ℃ for 20-36h to complete the chicken skin degreasing.

According to the scheme, in the step 1), the degreased chicken skin is sequentially treated by alkali liquor and alkaline protease solution, and gelatin is extracted to obtain a gelatin crude extract, and the method specifically comprises the following steps:

adding NaOH solution into defatted chicken skin, and changing the solution every 6-8h at 38-50 deg.C for 2-3 times; heating at 40-60 deg.C for 0.5-2 hr, centrifuging to obtain protein phase, stirring for 20-30 hr, pulping, centrifuging, adding alkaline protease solution and distilled water, extracting gelatin in water bath, and filtering to obtain crude gelatin extractive solution.

Preferably, the concentration of the NaOH solution is 0.04-0.06mol/L, and the mass-volume ratio of the degreased chicken skin to the NaOH solution is 1: 5.5-7 (g/mL).

Preferably, the centrifugation speed is 3500-.

Preferably, the concentration of the alkaline protease solution is 0.8-1.2mg/mL, and the mass-to-volume ratio of the protein phase to the alkaline protease solution is 1:1.8-2.5 (g/mL).

Preferably, in the water bath gel extraction, the water bath conditions are as follows: extracting at 40-60 deg.C for 30-40 min.

According to the scheme, in the step 3), the specific steps are as follows:

placing the fat-containing solution A in a high-pressure extraction tank, and stirring at 45-50 deg.C for 10-20min to completely evaporate diethyl ether; then adding water, starting a circulating pump to circulate the fat solution at 80-98 ℃, heating to 98 ℃, closing an exhaust valve, heating for 3-5 hours at 105-115 ℃ to obtain a mixture of water and the chicken skin oil, filtering, standing for 2-4 hours to separate oil from water to obtain crude chicken oil; separating the crude chicken oil by a tubular separator to obtain the chicken skin oil with the water content less than 0.1 percent.

According to the scheme, in the step 1), the mass ratio of the chicken skin gelatin to the chitosan to the polyol plasticizer is (4-6): (0.6-0.9): (0.98-1.32); in the step 4), the mass ratio of the chicken skin gelatin to the chicken skin oil to the luteolin is (4-6): 0.49-1.98: (0.098-0.147); in the step 5), the mass ratio of the chicken skin gelatin to the transglutaminase is (4-6): (0.0196-0.0528); the mass ratio of the water content in the chicken skin gelatin and the obtained edible fresh-keeping liquid is (4-6): (93.4-95.1).

According to the scheme, in the step 1), the concentration of the chicken skin gelatin solution is 8-15%, and the concentration of the chitosan solution is 1.2-2%.

According to the scheme, in the step 5), the catalytic crosslinking conditions are as follows: stirring for 35-50min at 48-55 ℃.

The application of the edible Daghestan chicken skin gelatin preservative solution is provided, and specifically, the product to be preserved is soaked in the preservative solution and taken out to be filmed and preserved, or the preservative solution is sprayed on the surface of the product to be preserved to be filmed and preserved. Preferably, the product to be preserved is an egg, a duck egg, a preserved egg, a salted egg or a fruit.

The preservation method of the edible preservative solution for luteolin chicken skin gelatin is provided, and concretely comprises the steps of filling the edible preservative solution into a sealed food-grade PET plastic pot or barrel, and storing at the temperature of 4-10 ℃.

The application of the luteolin chicken skin gelatin edible preservative film is provided, and specifically, the preservative film is packaged into a product to be preserved for preservation. Preferably, the product to be preserved is an egg, a duck egg, a preserved egg, a salted egg or a fruit.

The invention has the beneficial effects that:

1. the edible preservative solution and preservative film made of luteolin chicken skin gelatin provided by the invention take chicken skin gelatin and chitosan as basic preservative films, and the hydrophobicity of the preservative film is increased through chicken skin oil, so that the water vapor transmission rate of the gelatin film is reduced, that is, the water resistance of the gelatin film is improved, and the film forming time is shortened; in addition, the functional component luteolin has good antibacterial and antioxidant effects, and can be combined with chicken skin gelatin by hydrogen bonds, so that the space three-dimensional structure of gelatin molecules is changed into a more stable triple helix, the film forming property of gelatin is improved, and the mechanical property and the barrier capability of gelatin are enhanced.

2. The preservative solution has high film forming speed, the preservative film has strong mechanical property and barrier capability, and simultaneously has good antibacterial and antioxidant effects, and the application modes are flexible and various, so that the preservative solution can be soaked or sprayed to form a film for preservation, and can also be packaged for preservation after being formed into a film; the method has the specific application scenes of short-time temporary storage before sale or processing of eggs or duck eggs, fresh keeping of preserved egg and salted egg packaging, and the like, can also be used for fruit packaging, and has wide application prospect.

3. According to the invention, the chicken skin gelatin is prepared from chicken skin, and the chicken skin oil extracted from the fat-containing solution in the extraction process of the chicken skin gelatin is collected as a raw material, so that leftovers in the poultry processing industry are utilized in a high-value manner to a great extent; the chicken skin gelatin is extracted by combining alkali treatment and an alkaline protease method, the alkaline protease does not have lipase activity, the interference of chicken skin fat and targeted enzymolysis of chicken skin collagen can be eliminated, the high-efficiency extraction of collagen and the purity of the collagen are ensured, the required time is short, and the extraction rate is high; meanwhile, the chicken skin gelatin has low content of small molecular fragments with molecular weight less than 120kDa, high tensile strength, low water vapor transmission rate (MVP) and strong water resistance; the method is simple to operate, low in cost, good in effect when used in the preservation field and wide in application prospect.

Drawings

FIG. 1 is a technical route according to an embodiment of the present invention.

Detailed Description

The invention is further illustrated by the following examples.

In the following examples, the raw materials were prepared as follows:

1) the alkaline protease is APG1115 protease, available from Wuhan, such as Nature's Biotechnology Ltd. The APG1115 protease optimal temperature and pH value are 60 ℃ and 10.0 respectively. The enzyme has good pH stability: is stable at 30 deg.C and pH10.5 for 2 hr and at room temperature at pH 6.0-10.0 for 20 d.

2) Luteolin was purchased from veckcqi biotechnology limited, sikawa, CAS: 491-70-3, purity of 98% or more, and is flavonoid with antiinflammatory, antiallergic, antitumor, antibacterial, and antiviral physiological functions.

3) The extraction and preparation of the chicken skin gelatin are as follows:

a. separating chicken skin fat: cutting 1kg of fresh frozen chicken skin into powder of not more than 5mm multiplied by 5mm by a meat grinder, then weighing a proper amount of the chicken skin, putting the chicken skin into a 5L big beaker, adding a small amount of deionized water, absorbing water, swelling and dissolving for 10-20min, and then mixing the chicken skin with ether solution according to the mass volume ratio of 1:2(g/mL) in ether, left at 4 ℃ for 24h and then filtered in a fume hood. The filtered filtrate is kept at 4 ℃ for standby, and is marked as A1 liquid; the filter residue is remained to be used as the raw material B for preparing the gelatin.

b. Soaking in alkali liquor: respectively weighing the degreased chicken skin B, placing the degreased chicken skin B into a 2L beaker, and mixing the degreased chicken skin B with the raw materials in a proportion of 1: 1200mL of 0.05mol/L NaOH solution is added into 6(g/mL), the solution is replaced every 6 hours at 40 ℃ for 3 times to remove minerals, and the treated leather is white, has swelling and swelling volume and good elasticity.

c. Treating an enzyme solution: the chicken skin soaked in alkali liquor is pulped, heated for 1h at the temperature of 40 ℃ and then centrifuged at the speed of 4000r/min to obtain a partially defatted protein phase and a liquid phase. Stirring the protein phase for 24h, pulping and centrifuging, treating with alkaline protease APG1115 solution with the concentration of 1mg/mL after repeating the pulping and centrifuging steps twice, wherein the mass-to-volume ratio of the protein phase to the alkaline protease solution is 1:2(g/mL), and extracting collagen in the precipitate.

d. Carrying out water bath gel extraction: and (c) transferring the collagen subjected to enzymolysis in the step (c) to a beaker, and taking the mass of the collagen and the volume of distilled water as a feed-liquid ratio of 1:2(g/mL) and placing in a water bath at 50 ℃ for water bath gel extraction for 40 min. After water bath, the crude extract of gelatin is obtained by filtering with gauze.

e. Concentrating and drying: pouring the crude gelatin extractive solution into a separating funnel, standing, mixing the fat A2 on the upper layer of the gelatin solution with the A1 solution in (1) to obtain A, pouring the lower layer of gelatin solution into a beaker, and placing in a 40 deg.C constant temperature water bath kettle to prevent gelatin caused by low room temperature. And (3) putting the extract into a rotary evaporator for concentration to remove part of water, and putting the extract into a vacuum freeze dryer to obtain 144.0g of finished gelatin with the water content of less than 14%, wherein the extraction rate of the gelatin is 14.4%.

The traditional acid method for extracting gelatin is to add 3% hydrochloric acid to hydrolyze for more than 3.5h at 65 ℃, and the extraction rate is 8.2%; the extraction of gelatin by pepsin is carried out by adding 7000U/g pepsin and hydrolyzing at about 37 deg.C for 3h, and the extraction rate is 9.5%. The invention adopts alkali treatment-alkaline protease method combination, and APG1115 enzyme with the concentration of 5000U/g is added for hydrolysis for 2h at the temperature of 60 ℃, and the extraction rate is 14.4%. Compared with the traditional acid method for extracting gelatin and pepsin for extracting gelatin, the method has the advantages that the extraction time is short, and the extraction rate of gelatin is improved by 6%.

The APG1115 protease is serine alkaline protease, has high stability in the pH range of 6-10, has no lipase activity, can eliminate interference of chicken skin fat and targeted enzymolysis of chicken skin collagen, and can ensure high efficiency extraction of collagen and purity of collagen.

During the extraction of gelatin, the gelatin converted from collagen is a mixture of fragments with molecular weights between 80 and 250kDa due to the breaking of inter-and intra-chain covalent crosslinks. The gel strength of the gelatin is related to the molecular weight distribution of the gelatin, and the lower the content of the small molecular fragment with the molecular weight of less than 120kDa, the better the gel strength of the gelatin. The gelatin micromolecules extracted under the acidic condition account for 9.6 percent, the gelatin micromolecules extracted under the alkaline condition account for 8.55 percent, and the gelatin micromolecules subjected to alkali treatment-APG 1115 enzymolysis account for 7.2 percent. The gelatin treated by the alkali and subjected to enzymolysis by the APG1115 has the advantages that the gel strength is enhanced by about 10 percent compared with that of the gelatin treated by the acid method and pepsin, the tensile strength is higher, the water vapor transmission rate (MVP) is low, and the water resistance is higher. The properties of the gelatin obtained by different extraction processes are compared in table 1.

TABLE 1 comparison of the Properties of gelatin according to different extraction methods

4) The chicken skin oil is prepared by the following steps:

putting A in the step (1) e into a high-pressure extraction tank, soaking at 50 ℃, and stirring for 15min to completely evaporate diethyl ether; and (3) putting water into the high-pressure extraction tank again, wherein the mass ratio of the A to the water is 4: starting a circulating pump at the temperature of 1, 95 ℃ for circulation, heating to 98 ℃, closing an exhaust valve, and heating for 4 hours at the temperature of 110 ℃ to obtain a mixture of water and chicken skin oil; filtering the oil-water mixture by using a duplex filter, standing for 4 hours, and separating oil from water to obtain crude chicken oil; separating the crude chicken oil by a tubular separator to obtain the chicken skin oil with the water content less than 0.1 percent.

Example 1

The preparation method of the edible trifoliol vegetable chicken skin gelatin fresh-keeping liquid comprises the following steps:

(1) dissolving 4 parts of chicken skin gelatin in 36 parts of deionized water, absorbing water, fermenting for 20 minutes, dissolving in a water bath at 50 ℃, and stirring and homogenizing for 40 minutes to prepare a 10% (w/v) gelatin solution;

(2) dissolving 0.9 part of chitosan in 59.1 parts of 1.0% diluted acetic acid solution to prepare 1.5% (w/v) chitosan solution, mixing with the gelatin solution to form a chitosan/gelatin (w/w) mixed solution, respectively adding 1.98 parts of chicken skin fat oil, 1.32 parts of sorbitol and 0.147 part of luteolin into the mixed solution at room temperature, and stirring the mixture for 30min at 50 ℃ by using a magnetic stirrer until the chitosan solution is completely dissolved.

(3) Neutralizing the prepared mixed solution with 0.25mol/L NaOH solution until the pH value is 6, adding 0.0528 parts of transglutaminase (TGase), continuously stirring at 50 ℃ for 40min, heating to boil and inactivate the enzyme for 10min, cooling to room temperature, and performing vacuum defoaming to obtain the preservative solution.

The oil is adopted to improve the hydrophobicity of the gelatin-chitosan-based preservative film, reduce the water vapor transmission rate of the gelatin film and improve the water resistance of the gelatin film. According to the embodiment of the invention, the chicken skin oil extracted from the chicken skin oil removed in the chicken skin gelatin extraction process is used for replacing vegetable oil, the film forming time is shortened, the chicken skin is utilized to the maximum extent, the cost of the film is also reduced, and the influence results of different oils on the film performance are shown in table 2.

TABLE 2 Effect of different oils on preservative film Performance

The functional component, luteolin, is added into the fresh-keeping liquid of the embodiment of the invention, is a natural plant extract, and has excellent oxidation resistance and antibacterial activity. The hydroxyl radical scavenging ability of the compound is stronger than that of tea polyphenol, and the compound has strong inhibiting effect on egg spoilage bacteria and pathogenic bacteria, especially staphylococcus aureus, escherichia coli and the like. Furthermore, luteolin has good heat resistance, and the oxidation resistance (free radical clearance) of luteolin is not influenced even when the luteolin is treated at 180 ℃ for 2 hours, so that the oxidation of the added chicken skin oil and the oxidation of a fresh-keeping product are inhibited in the subsequent film-making and temperature-raising process. Luteolin can be combined with chicken skin gelatin through hydrogen bonds, so that the alpha-helix and irregular coil content of gelatin molecules is reduced, the beta-turn content is increased, the disordering degree is higher, the space three-dimensional structure is changed into more stable tri-helix, namely luteolin improves the film forming performance of gelatin, the force performance and the barrier capability are stronger, and the results are shown in table 3.

TABLE 3 determination of antibacterial, antioxidant and protein secondary structure of epidermal gelatin

Index (I)	Adding luteolin	Without adding luteolin
			Escherichia coli/mm	2.41	0.00
Staphylococcus aureus zone/mm	3.65	0.00
			Free radical clearance/%)	51.33	2.71
Alpha-helix/%)	41.13	43.58
			Beta-turn/%)	6.34	3.95
Beta-sheet/%)	51.25	46.15
			Random crimp/%)	2.74	4.02

And (3) placing the fresh duck eggs which need to be temporarily stored before processing into the preservation solution obtained in the embodiment, soaking for 5s, taking out, blowing to dry at room temperature to form a film, and carrying out performance detection.

The coated fresh duck eggs obtained in example 1 and uncoated fresh duck eggs were stored at room temperature for 7 days, and the results of measurement of microbial indicators are shown in table 4.

TABLE 4 microbial test results of coated and uncoated fresh duck eggs

The respiration intensity, weight loss ratio and harderian unit test were performed on the coated fresh duck eggs and the uncoated fresh duck eggs of example 1, and the results are shown in table 5.

TABLE 5 breath strength, weight loss ratio, Ha's unit test results of coated and uncoated fresh duck eggs

Example 2

The preparation method of the edible trifoliol vegetable chicken skin gelatin fresh-keeping liquid comprises the following steps:

(1) dissolving 6 parts of chicken skin gelatin in 54 parts of deionized water, absorbing water, fermenting for 15 minutes, dissolving in a 45 ℃ water bath, and stirring to homogenize for 30 minutes to prepare a 10% (w/v) gelatin solution;

(2) dissolving 0.6 part of chitosan in 39.4 parts of 1.0% diluted acetic acid solution to prepare 1.5% (w/v) chitosan solution, and mixing with the 10% (w/v) gelatin solution to prepare chitosan/gelatin (w/w) mixed solution;

(3) respectively adding 0.49 parts of chicken skin oil, 0.98 parts of sorbitol and 0.098 parts of luteolin into the mixed solution at room temperature, and stirring for 40min at 50 ℃ by using a magnetic stirrer until the mixture is completely dissolved;

(4) neutralizing the prepared mixed solution with 0.25mol/L NaOH solution until the pH value is 6, adding 0.02 part of TGase, continuously stirring for 40min at 50 ℃, heating to boil and deactivate the enzyme for 10min, cooling to room temperature, then carrying out vacuum pressure reduction and defoaming, carrying out tape casting on a horizontal clean polyvinyl chloride plate with edges to form a film, stripping the film, washing with deionized water to be nearly neutral, and naturally drying at room temperature.

The obtained film-sealed and packaged mature salted egg is subjected to quality index measurement in the storage period, and compared with the PE film-packaged and unpacked salted egg, the results are shown in tables 6 and 7.

TABLE 6 determination of total number of colonies of contents of salted eggs packaged in different packaging methods (n ═ 30, CFU/g)

TABLE 7 comparison of sensory scores of salted eggs packaged in different ways after 180 days of storage

The present invention is not limited to the above preferred embodiments, but rather, any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.