Edible coating material capable of preventing dry loss and resisting oxidation under low-temperature condition as well as preparation method and application of edible coating material

Abstract

The invention provides an edible coating material capable of preventing dry loss and resisting oxidation under a low-temperature condition as well as a preparation method and application of the edible coating material, and belongs to the technical field of food coating. According to the edible coating material, the A-type gelatin and the trehalose dihydrate serve as coating matrixes, antioxidant active substance tea polyphenol nano-particles and sustainable release active ingredients are added, a heating reaction is conducted to obtain coating liquid, the coating liquid is sprayed to the surface of food to serve as a coating fresh-keeping material, coating of the food can be effectively achieved, and the edible coating material has the advantages of being environmentally friendly and free of toxic and side effects. A barrier is formed between the food and an air system, so that the storage stability of the food is guaranteed, the dry loss oxidation of the food can be slowed down at the temperature of-20 DEG C to-50 DEG C, the problems of oxidation weight loss, dry loss and the like in the freezing low-temperature storage process of the food are solved, and a new strategy is provided for fresh keeping of the frozen food.

Description

Technical Field

[0001] The present invention relates to the technical field of food coatings, and in particular to an edible coating material that is dry-out-resistant and oxidation-resistant under low-temperature conditions, and a preparation method and application thereof. Background Art

[0002] While frozen storage can extend the shelf life of foods rich in fat and protein (such as meat, fish, and poultry), prolonged freezing can lead to oxidation and dehydration, also known as "freezer burn." Freezer burn occurs when temperature fluctuations and inadequate packaging during frozen storage cause ice crystals to sublime, reducing the moisture content on the food's surface. Over time, this ice crystals push inward, forming a dry, porous structure. This increased contact area with oxygen triggers lipid and protein oxidation, ultimately resulting in food deterioration, including weight loss, grayish-white surface patches, hardened texture, and the development of rancid odors and other unpleasant flavors. This deterioration severely impacts the food's nutritional value and sensory qualities.

[0003] Through analysis of the current research status, patent CN119463033A provides a supramolecular hydrogel coating that can reversibly adhere to frozen food, as well as its production method and application. However, the preparation process of this invention is cumbersome, and reversible desorption can only be achieved under specific wavelength light, and it does not reflect the protective effect on frozen food.

[0004] Therefore, developing an edible coating with good anti-drying and antioxidant capabilities under conditions of -20℃~-50℃, thereby slowing down the rate of food oxidation and drying during frozen storage, is of great significance for ensuring the storage stability of frozen foods and meeting people's new demand for healthy and nutritious foods. Summary of the Invention

[0005] The purpose of the present invention is to provide an edible coating material that is anti-drying and anti-oxidative under low temperature conditions, as well as a preparation method and application thereof. The edible coating material has good anti-drying and anti-oxidation capabilities under low temperature conditions of -20°C to -50°C, and has good barrier properties, forming a barrier between food and the air system, reducing the occurrence of food oxidation, dryness, etc., ensuring product quality, and extending shelf life.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides an edible coating material that is anti-drying and anti-oxidative under low temperature conditions, comprising the following raw materials in parts by mass: 3-5 parts of type A gelatin, 4-6 parts of trehalose dihydrate, 0.09-0.9 parts of tea polyphenol nanoparticles, 0.15-0.2 parts of plasticizer, and 87.9-92.76 parts of water; The preparation method of the tea polyphenol nanoparticles comprises the following steps: mixing chitosan with acetic acid to obtain a chitosan solution; mixing pectin with water to obtain a pectin solution; Tea polyphenols are mixed with the pectin solution, chitosan solution is added to the obtained mixed solution, and the pH value is adjusted to 3-6. After coating, ultrasonic treatment and freeze drying are sequentially performed to obtain tea polyphenol nanoparticles.

[0007] Preferably, the concentrations of the chitosan solution and the pectin solution are independently 1-3 mg / mL.

[0008] Preferably, hydrochloric acid is used to adjust the pH value; the mass ratio of the chitosan, pectin and tea polyphenols is (0.1~0.2):(0.1~0.2):(0.08~0.1); the mass concentration of the acetic acid is 0.5~1%; and the mass concentration of the hydrochloric acid is 0.05~0.5 mol / L.

[0009] Preferably, the coating time is 1 to 2 hours; the ultrasonic treatment conditions include: ultrasonic power of 300 to 500 W, and time of 5 to 15 minutes.

[0010] Preferably, the particle size of the tea polyphenol nanoparticles is 400-900 nm; and the plasticizer is glycerol.

[0011] The present invention provides a method for preparing an edible coating material that is anti-drying and anti-oxidative under low temperature conditions as described in the above technical solution, comprising the following steps: Type A gelatin, trehalose dihydrate and water are mixed, tea polyphenol nanoparticles are added, heated for reaction, a plasticizer is added, and the gas is exhausted to obtain an edible coating material that is anti-drying and anti-oxidative under low temperature conditions.

[0012] Preferably, the temperature of the heating reaction is 40-50° C., and the time is 30-60 min; and the time of the exhaust is 10-30 min.

[0013] The present invention provides an edible coating material that is anti-drying and anti-oxidation under low temperature conditions as described in the above technical solution, or an edible coating material that is anti-drying and anti-oxidation under low temperature conditions prepared by the preparation method described in the above technical solution, and its application in food protection under low temperature conditions.

[0014] Preferably, the low temperature condition is -20°C to -50°C.

[0015] Preferably, the food is a cooked or semi-cooked meat product.

[0016] The present invention provides an edible coating material that is anti-drying and anti-oxidative under low-temperature conditions. The coating material uses type A gelatin and trehalose dihydrate as coating matrices, and is added with antioxidant active substance tea polyphenol nanoparticles, which can continuously release active ingredients. A coating liquid is obtained by heating reaction, and the coating liquid is sprayed onto the surface of food as a coating preservation material. The coating can effectively achieve food coating and form a barrier between the food and the air system. On the one hand, it can isolate the food from oxygen and water vapor in the environment during subsequent frozen storage, and continuously release active substances to play an antioxidant role. On the other hand, the trehalose dihydrate fully combines with the surrounding water molecules, regulates the spatial distribution and mobility of the water molecules, thereby preventing food tissue from being destroyed by ice crystals during frozen storage and slowing down the sublimation rate of ice crystals, thereby effectively preventing the occurrence of problems such as oxidation and dry loss of food during frozen storage, which is beneficial to ensuring the storage stability of the food. The dry loss and oxidation of food can be slowed down under the conditions of -20°C to -50°C, thereby solving the problems of oxidative weight loss and dry loss of food during frozen and low-temperature storage, and providing a new strategy for preserving frozen food.

[0017] The present invention uses an electrostatic self-assembly method to prepare polyelectrolyte tea polyphenol nanoparticles without a chemical crosslinker. Chitosan is protonated under acidic conditions and cross-linked with negatively charged pectin to form a complex, encapsulating tea polyphenol as an antioxidant active substance within the complex. Encapsulating tea polyphenol within the nanoparticles significantly reduces the loss of active tea polyphenol during the packaging process while ensuring long-term, slow release of the active substance. Ultrasonic treatment is also used to break the complex into nanoscale particles through the mechanical and cavitation effects of the ultrasonic treatment, reducing the particle size and facilitating uniform dispersion within the coating matrix for slow release of the active ingredient.

[0018] The preparation method of the edible coating material provided by the present invention has simple process operation, mild conditions, is easy to realize industrial production, and the preparation raw materials are all food processing materials, and the obtained coating liquid is edible. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the particle size distribution diagram of the tea polyphenol nanoparticles prepared in Example 1. DETAILED DESCRIPTION

[0020] In the present invention, unless otherwise specified, the required raw materials or reagents are commercially available products well known to those skilled in the art.

[0021] The present invention provides an edible coating material that is anti-drying and anti-oxidative under low temperature conditions, comprising the following raw materials in parts by mass: 3-5 parts of type A gelatin, 4-6 parts of trehalose dihydrate, 0.09-0.9 parts of tea polyphenol nanoparticles, 0.15-0.2 parts of plasticizer, and 87.9-92.76 parts of water; The preparation method of the tea polyphenol nanoparticles comprises the following steps: mixing chitosan with acetic acid to obtain a chitosan solution; mixing pectin with water to obtain a pectin solution; Tea polyphenols are mixed with the pectin solution, chitosan solution is added to the obtained mixed solution, and the pH value is adjusted to 3-6. After coating, ultrasonic treatment and freeze drying are sequentially performed to obtain tea polyphenol nanoparticles.

[0022] In the present invention, the mass fraction of the type A gelatin is more preferably 3.5 to 4.5 parts, and further preferably 4 parts; the mass fraction of the trehalose dihydrate is more preferably 4.5 to 5.5 parts, and further preferably 5 parts; the mass fraction of the tea polyphenol nanoparticles is more preferably 0.09 to 0.9 parts, and further preferably 0.18 to 0.45 parts; the mass fraction of the plasticizer is more preferably 0.16 to 0.19 parts, and further preferably 0.18 parts; and the mass fraction of the water is more preferably 90.82 parts.

[0023] The present invention has no particular limitation on the sources and specifications of the pectin and tea polyphenols; any commercially available products known in the art may be used.

[0024] In the present invention, the concentrations of the chitosan solution and the pectin solution are independently preferably 1-3 mg / mL, more preferably 1-2 mg / mL.

[0025] In the present invention, the mass concentration of the acetic acid is preferably 0.5-1%, more preferably 0.6-1%. The amount of acetic acid used in the present invention can reach the desired concentration of the chitosan solution.

[0026] In the present invention, after the tea polyphenols are mixed with the pectin solution, the concentration of the tea polyphenols in the obtained mixed solution is preferably 0.8-1.2 mg / mL, more preferably 0.8-1.0 mg / mL.

[0027] In the present invention, the chitosan solution is preferably added dropwise to the mixed solution of tea polyphenols and pectin solution at a stirring speed of 300 rpm / min.

[0028] The present invention preferably uses hydrochloric acid to adjust the pH value, more preferably adjusting the pH value to 4-5; the concentration of the hydrochloric acid is preferably 0.05-0.5 mol / L, more preferably 0.1-0.2 mol / L. The amount of hydrochloric acid used in the present invention is preferably sufficient to achieve the desired pH value.

[0029] In the present invention, the mass ratio of chitosan, pectin and tea polyphenols is preferably (0.1-0.2):(0.1-0.2):(0.08-0.1), more preferably (0.1-0.15):(0.1-0.15):(0.08-0.09), and further preferably 0.1:0.1:0.08.

[0030] In the present invention, the coating time is preferably 1-2 h, more preferably 1.5-2 h; the ultrasonic treatment conditions preferably include: ultrasonic power of 300-500 W, more preferably 400-450 W, time of 5-15 min, more preferably 10-12 min.

[0031] The present invention has no particular limitation on the freeze-drying, and the freeze-drying may be carried out according to a process well known in the art.

[0032] In the present invention, the particle size of the tea polyphenol nanoparticles is preferably 400-900 nm.

[0033] In the present invention, the plasticizer is preferably glycerol.

[0034] In the present invention, gelatin exhibits excellent safety, biodegradability, and gas barrier properties. Trehalose dihydrate, a disaccharide formed by two glucose molecules bound together by a glycosidic bond, contains multiple hydroxyl groups and possesses extremely strong hydration capacity, forming a more rigid trehalose / water structure with enhanced resistance to freeze-dehydration. Furthermore, trehalose dihydrate effectively inhibits ice crystal formation and recrystallization by disrupting the organization of water molecules near the ice interface. The presence of trehalose dihydrate also regulates the spatial distribution and mobility of surrounding water molecules, thereby preventing ice crystal damage to food structures during frozen storage. Tea polyphenols, as antioxidants, are susceptible to inactivation due to their low stability and high sensitivity, making them inactive, which prevents significant improvement in the long-term antioxidant activity of the coating. The present invention encapsulates tea polyphenols within nanoparticles, significantly reducing the loss of active tea polyphenols during packaging while ensuring long-term, slow release of the active substances. The excellent film-forming properties of gelatin, the antifreeze properties of trehalose dihydrate, and the resulting tea polyphenol nanoparticles provide long-term release of antioxidants. The edible coating material provided by the present invention has good anti-drying and anti-oxidation capabilities under the conditions of -20°C to -50°C.

[0035] The present invention provides a method for preparing an edible coating material that is anti-drying and anti-oxidative under low temperature conditions as described in the above technical solution, comprising the following steps: Type A gelatin, trehalose dihydrate and water are mixed, tea polyphenol nanoparticles are added, heated for reaction, a plasticizer is added, and the gas is exhausted to obtain an edible coating material (coating liquid) that is anti-drying and anti-oxidative under low temperature conditions.

[0036] In the present invention, the heating reaction temperature is preferably 40-50°C, more preferably 45-50°C, and the duration is preferably 30-60 minutes; the degassing time is preferably 10-30 minutes. During the heating process, strong hydrogen bonds are formed between the gelatin and the trehalose dihydrate, forming a dense coating structure.

[0037] The present invention provides an edible coating material that is anti-drying and anti-oxidation under low temperature conditions as described in the above technical solution, or an edible coating material that is anti-drying and anti-oxidation under low temperature conditions prepared by the preparation method described in the above technical solution, and its application in food protection under low temperature conditions.

[0038] In the present invention, the low temperature condition is -20°C to -50°C.

[0039] In the present invention, the food is preferably a cooked or semi-cooked meat product.

[0040] The present invention preferably sprays the edible coating material evenly on the food and dries it to obtain a food with an anti-drying and anti-oxidation edible coating film. The present invention has no particular limitation on the spraying amount, which can be adjusted according to actual needs. In the embodiment of the present invention, the coating amount is specifically 1 mL / cm 3 .

[0041] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0042] The experimental methods described in the embodiments of the present invention are conventional methods unless otherwise specified; the following reagents and raw materials are commercially available unless otherwise specified.

[0043] The “parts” in the embodiments of the present invention are all based on mass.

[0044] In the following examples, type A gelatin (CAS No. 9000-70-8) was derived from source leaves and was brand S25197; Trehalose dihydrate, from McLean, brand D818474; Pectin (CAS No. 9000-69-5) was obtained from Maclean, brand P816453; Tea polyphenols (CAS No.: 84650-60-2) were obtained from Maclean, with the brand name T861565.

[0045] Example 1

[0046] The edible coating material provided in this embodiment is prepared from the following raw materials, calculated by weight: 4 parts of type A gelatin, 5 parts of trehalose dihydrate, 0.9 parts of tea polyphenol nanoparticles, 0.18 parts of glycerol, and 90.82 parts of water.

[0047] The preparation method of the edible coating material comprises the following steps: Preparation of tea polyphenols nanoparticles: 0.1 g of chitosan was dissolved in 1% acetic acid to obtain a chitosan solution with a concentration of 1 mg / mL. 0.1 g of pectin was dissolved in deionized water and stirred overnight to obtain a pectin solution with a concentration of 1 mg / mL. 0.08 g of tea polyphenols was dissolved in the pectin solution to make its concentration 0.8 mg / mL. Then, the chitosan solution was added dropwise to the pectin solution at a stirring speed of 300 rpm / min, and the pH value was adjusted to 5 with 0.1 mol / L hydrochloric acid. The mixture was stirred for 2 h, and the solution was ultrasonicated at a power of 400 W for 10 min (the ultrasonic on and off time were both 2 seconds). The solution was then freeze-dried to obtain nanoparticles loaded with tea polyphenols, and the particle size of the nanoparticles was kept at 400~900 nm. Figure 1 ; Preparation of edible coating material: 4 g of type A gelatin and 5 g of trehalose dihydrate were dissolved in 90.82 mL of water, 0.9 g of tea polyphenol nanoparticles were added (i.e., the tea polyphenol nanoparticles accounted for 10% of the total mass of type A gelatin and trehalose dihydrate), and the mixture was heated in a 50°C water bath for 30 min. 0.18 g of glycerol was added, and then the mixture was cooled to room temperature and degassed for 30 min to obtain a coating liquid, which was the edible coating material, recorded as S1.

[0048] Examples 2-3

[0049] The preparation methods of Examples 2 and 3 are the same as those of Example 1, with the only difference being that the added amounts of tea polyphenol nanoparticles are different, as shown in Table 1. The obtained coating solutions are respectively designated as S2 and S3.

[0050] Table 1 Ratio of raw materials in Examples 2 and 3

[0051] Comparative Example 1

[0052] The only difference from Example 1 is that the amount of tea polyphenol nanoparticles added is 0, and the resulting coating liquid is recorded as D1.

[0053] Comparative Example 2

[0054] The only difference from Example 1 is that the preparation step of tea polyphenol nanoparticles is removed, and commercially available tea polyphenol (CAS No.: 84650-60-2) McLean, brand T861565) is used to replace the tea polyphenol nanoparticles in Example 1 to obtain a coating liquid, which is recorded as D2.

[0055] Performance Testing

[0056] The water vapor transmission rate, antioxidant activity, dry weight loss rate, and peroxide value increase rate of the coated food were tested for S1-S3 and D1-D2 in Examples 1-3 and Comparative Examples 1-2, respectively. The testing methods are as follows: (1) Water vapor transmission rate test of coating liquid The water vapor transmission rate is determined according to GB 1037-1988 using the pseudo-cup method: anhydrous calcium chloride is placed in a mortar and placed in a drying oven to completely remove moisture. After cooling, 3 g of dried anhydrous calcium chloride is weighed and placed in a 50 mL wide-mouthed conical flask. The flask is tightly sealed with the coating sample to be tested and placed in a desiccator filled with a saturated potassium chloride solution. The flask is weighed every 12 hours for one week. The water vapor transmission coefficient is calculated based on the increase in cup weight according to the following formula:

[0057] Where: WVP-water vapor transmission coefficient (g·mm / m 2 ·d·kPa); Δm-water vapor migration (g / h·m 2 ); A-sample area (m 2 ); t - measurement time (h); L - sample thickness (mm); Δ P - Water vapor pressure difference on both sides of the sample (kPa); 24-24h; The saturated water vapor pressure of pure water at 25°C is 3.1671 kPa, and the water vapor pressure of a saturated KCl solution is 83% of that of pure water.

[0058] (2) Antioxidant activity test of coating liquid

[0059] The DPPH free radical scavenging test was conducted using the following method: the coating solution was diluted 10-fold and added to a freshly prepared DPPH-ethanol solution (0.8 mmol / L). The solution was allowed to react in the dark for 30 minutes, and the absorbance was measured at 517 nm using a UV spectrophotometer. Ethanol was used as a blank instead of the sample.

[0060]

[0061] Where: A1-absorbance of the sample after reaction with DPPH solution; A2-absorbance of the sample after reaction with ethanol solution; A0- absorbance after reaction of water and DPPH solution.

[0062] (3) Dry weight loss test of coated beef samples

[0063] Fresh beef samples were cooked, fished out to dry the surface moisture, cut into blocks to ensure uniform size, and evenly sprayed with the coating liquids of Examples 1 to 3 and Comparative Examples 1 to 2, respectively, with a coating amount of 1 mL / cm 3 , and dried for 10 minutes to obtain a food with an edible coating.

[0064] After drying, the coated foods were divided into two groups. One group was placed in a freezer alternately at -20°C and -50°C for one month, for a total of six months; the other group was kept at a constant temperature of -50°C for six months. The weight change and oxidation status of the different samples were measured at room temperature. The samples were thawed at 4°C for 24 hours before measurement.

[0065] The weight of beef frozen sprayed with different coating liquids was measured before and after six months of storage, and the weight change caused by freezing was calculated using the following formula:

[0066] Where: X-sample weight loss rate, %; W0-initial weight of cooked beef after drying, in grams (g); W1 - weight of cooked beef after six months of freezing, in grams (g).

[0067] (4) Peroxide value increase rate test of coated beef samples

[0068] Refer to GB5009.227-2016 "National Food Safety Standard for the Determination of Peroxide Value in Foods" to determine the peroxide value of different samples. Place the beef sample in a 250mL iodine bottle and add 5mL of a mixture of chloroform and glacial acetic acid (2:3, V:V) to completely dissolve the sample. Add 1.00mL of saturated potassium iodide solution, shake gently for 0.5 minutes, and then place in the dark for 3 minutes. Take out and add 50mL of water. After shaking well, immediately titrate with 0.01mol / L sodium thiosulfate standard titration solution. When it turns light yellow, add 1mL of starch indicator and continue titrating until the blue color of the solution disappears. Calculate the peroxide value of the sample according to the following formula:

[0069] Where: POV-peroxide value, unit is grams per hundred grams (g / 100g); V-volume of sodium thiosulfate standard titration solution consumed by the sample, in milliliters (mL); V0-the volume of sodium thiosulfate standard titration solution consumed by the blank sample, in milliliters (mL); c-concentration of sodium thiosulfate standard titration solution, in moles per liter (mol / L); 0.1269: The mass of iodine equivalent to 1.00 ml of sodium thiosulfate standard titration solution (c(Na2S2O3) = 1.000 mol / L), expressed in grams per millimole (g / mmol); m-sample mass, in grams (g); 100-Conversion factor for 100g sample.

[0070] The peroxide value increase rate was calculated using the following formula:

[0071] Wherein: X-peroxide value increase rate, %; POV0 - initial peroxide value of cooked beef, in grams (g / 100g); POV1 - Peroxide value of cooked beef frozen for six months, in grams (g / 100g).

[0072] The test results are shown in Tables 2 to 4.

[0073] Table 2 Water vapor transmission rate of coating liquid in different cases

[0074] Table 3 Antioxidant activity test of coating solutions in different cases

[0075] Table 4 Dry weight loss rate and peroxide value increase rate of beef samples sprayed with coating liquid of Examples 1 to 3 and Comparative Examples 1 to 2

[0076] Tables 2-4 demonstrate that the coating prepared by the present invention exhibits excellent barrier properties and antioxidant capacity. The water vapor transmission rates of Examples 1-3 were all lower than those of the control (Comparative Example 2). Furthermore, the coating effectively mitigated the oxidative weight loss of beef, whether heated at -20°C to -50°C or at a constant temperature of -50°C. At -50°C, Example 1 exhibited the lowest dry weight loss and peroxide value increase, at 3.87% and 4.6%, respectively. In antioxidant activity testing, the freshly prepared coating from Example 1 exhibited slightly lower antioxidant activity than that of Comparative Example 2. This is due to the inability of nanoparticle encapsulation to rapidly release a significant amount of tea polyphenol active substances. In subsequent tests, the antioxidant activity of Example 1 consistently exceeded that of Comparative Example 2, demonstrating that the antioxidant activity of free tea polyphenols is significantly affected by the environment, while nanoparticle encapsulation enhances the stability of the tea polyphenols, facilitating the prolonged release of active substances. In contrast, in Comparative Example 1, in which no antioxidant active substance tea polyphenols was added, the antioxidant activity test index was significantly lower than that of Examples 1 to 3, and the water vapor permeability, weight loss rate and peroxide value of the coated food were significantly higher than those of the other examples.

[0077] In summary, the edible coating provided by the present invention exhibits excellent water and oxygen barrier properties (anti-drying) and antioxidant properties at temperatures between -20°C and -50°C, and is edible. During frozen storage, it isolates food from ambient oxygen and water vapor, improving storage stability and ensuring food quality. This coating has promising application prospects in frozen food storage.

[0078] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. An edible coating material that is resistant to drying and oxidation under low temperature conditions, characterized in that: The preparation comprises the following raw materials in parts by weight: 3-5 parts of type A gelatin, 4-6 parts of trehalose dihydrate, 0.09-0.9 parts of tea polyphenol nanoparticles, 0.15-0.2 parts of plasticizer, and 87.9-92.76 parts of water; The preparation method of the tea polyphenol nanoparticles comprises the following steps: mixing chitosan with acetic acid to obtain a chitosan solution; mixing pectin with water to obtain a pectin solution; Tea polyphenols are mixed with the pectin solution, chitosan solution is added to the obtained mixed solution, and the pH value is adjusted to 3-6. After coating, ultrasonic treatment and freeze drying are sequentially performed to obtain tea polyphenol nanoparticles.

2. The edible coating material that is anti-drying and anti-oxidative under low temperature conditions according to claim 1, characterized in that: The concentrations of the chitosan solution and the pectin solution are independently 1-3 mg / mL.

3. The edible coating material that is anti-drying and anti-oxidative under low temperature conditions according to claim 1, characterized in that: The pH value is adjusted using hydrochloric acid; the mass ratio of the chitosan, pectin and tea polyphenols is (0.1-0.2):(0.1-0.2):(0.08-0.1); the mass concentration of the acetic acid is 0.5-1%; and the mass concentration of the hydrochloric acid is 0.05-0.5 mol / L.

4. The edible coating material that is anti-drying and anti-oxidative under low temperature conditions according to claim 1 or 3, characterized in that: The coating time is 1 to 2 hours; the ultrasonic treatment conditions include: ultrasonic power of 300 to 500 W, and time of 5 to 15 minutes.

5. The edible coating material that is anti-drying and anti-oxidative under low temperature conditions according to claim 1, characterized in that: The particle size of the tea polyphenol nanoparticles is 400-900 nm; and the plasticizer is glycerol.

6. The method for preparing the edible coating material that is anti-drying and anti-oxidative under low temperature conditions according to any one of claims 1 to 5, characterized in that: The following steps are involved: Type A gelatin, trehalose dihydrate and water are mixed, tea polyphenol nanoparticles are added, heated for reaction, a plasticizer is added, and the gas is exhausted to obtain an edible coating material that is anti-drying and anti-oxidative under low temperature conditions.

7. The preparation method according to claim 6, characterized in that The temperature of the heating reaction is 40-50° C., and the time is 30-60 minutes; the time of the exhaust is 10-30 minutes.

8. Use of the edible coating material that prevents desiccation and oxidation under low temperature conditions according to any one of claims 1 to 5 or the edible coating material that prevents desiccation and oxidation under low temperature conditions prepared by the preparation method according to claim 6 or 7 in food protection under low temperature conditions.

9. The use according to claim 8, characterized in that The low temperature condition is -20°C to -50°C.

10. The use according to claim 9, characterized in that The food is a cooked or semi-cooked meat product.

Images