A dry-aging food source-based active coating for ultra-low temperature conditions and a preparation method thereof

Abstract

The application provides an edible active coating for preventing dry consumption under an ultralow temperature condition and a preparation method, and belongs to the technical field of active packaging. The application combines double-layer coatings, inhibits free radical oxidation generated by freezing through an inner antioxidant, and effectively locks water and blocks external oxygen permeation through the synergistic effect of an outer high-barrier structure, thereby significantly improving the freezing preservation effect of food, and the raw materials are natural and safe, the preparation method is reasonable, and the application has good practical application value. The application solves the problems of poor effects of edible freezing protection coatings suitable for extremely cold environments in the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of food active packaging, and particularly relates to a kind of food source base active coating for preventing dry consumption under ultra-low temperature condition and preparation method. BACKGROUND

[0002] Low-temperature frozen storage is one of the commonly used means to extend the shelf life of food. However, the freezing process can have adverse effects on the taste characteristics and nutritional value of food. Although the formation of large ice crystals can be effectively inhibited under ultra-low temperature freezing conditions of-20℃ to-50℃, micro-ice crystals can still penetrate cell structures such as muscle fibers of meat or cell walls of fruits and vegetables during rapid freezing. With the extension of storage time, the color of the food surface gradually darkens, and the moisture and starch content also show a downward trend, and the phenomenon of dry consumption of food gradually becomes serious. Frozen dry consumption refers to the phenomenon of weight loss and quality decline due to water sublimation or evaporation during freezing or long-term frozen storage of food. This process mainly involves the loss of water on the surface and shallow layer of food, which is manifested as dryness, discoloration, and rough texture.

[0003] To solve the key problems such as serious dry loss, quality deterioration and so on in the super-low temperature (-20℃-50℃) storage in cold regions, such as reducing water loss during frozen storage, maintaining the flavor and texture of the product, reducing fat oxidation and prolonging the shelf life, developing edible frozen protective coating technology suitable for extreme cold environment has become an important innovation direction and technical breakthrough in the field of super-low temperature food engineering. The method disclosed in the Chinese invention patent number CN119498393A "ice coating liquid for mussels and preparation method and application thereof" uses an ice coating liquid mainly composed of propylene glycol and xanthan gum for mussel preservation. The ice coating in this invention is thick and heavy, which reduces the economic benefits during transportation and storage, and the application of ice coating also increases the difficulty of eating. The method disclosed in the Chinese invention patent number CN113995012A "a method for preserving and storing macadamia nuts" provides a low-temperature preservation method for nuts, but it does not study the storage of nuts in such super-low temperature environment as -(20-50)℃. The method disclosed in the Chinese invention patent number CN119744901A "anti-ice crystal frozen dough and its application in baked foods" uses an anti-freeze peptide and a polyphenol to form a conjugate, and the gel made of the conjugate is added to the dough to improve the easy oxidation characteristics of the dough during frozen storage. However, this kind of strategy based on glycosylation conjugate may face challenges in maintaining the integrity of gel network structure and the sustained release efficiency of active ingredients in deep cold or super-low temperature environment with drastic temperature fluctuations. The Chinese invention patent number CN119817641A "a method for preserving vegetables based on super-low temperature quick-freezing technology" uses super-low temperature technology to freeze and preserve vegetables, but it directly adds antioxidants, which lose activity quickly. Therefore, in order to solve the above problems, it is urgent to explore new dry-loss-preventing food-based active coating. SUMMARY

[0004] The present application solves the problem of poor effect of edible frozen protective coating suitable for extreme cold environment in the prior art.

[0005] A preparation method of a dry-loss-preventing food-based active coating under super-low temperature conditions, the preparation method is as follows:

[0006] S1: mixing egg white protein and water to prepare an egg white protein solution; dissolving ferulic acid in an 80% ethanol solution to prepare a ferulic acid solution;

[0007] S2: mixing the ferulic acid solution and the egg white protein solution, adjusting the pH with NaOH solution to obtain a mixed solution, and using an ultrasonic cell disruptor to perform ultrasonic treatment on the solution; then performing centrifugation and dialysis treatment to obtain an inner layer composite coating solution;

[0008] S3: corn alcohol-soluble protein is dissolved in 80% ethanol to obtain a corn alcohol-soluble protein solution; sodium alginate is added to water to obtain a sodium alginate solution;

[0009] S4: the corn alcohol-soluble protein solution is added to the sodium alginate solution, and glycerol is added to stir uniformly in a water bath to obtain an outer layer composite coating solution.

[0010] Preferably, the mass / volume ratio of egg white protein to water in the egg white protein solution of S1 is 2:95, and the mass / volume ratio of ferulic acid to 80% ethanol solution in the ferulic acid solution is 8-16:1.

[0011] Preferably, the mass of ferulic acid is 2%-6% of the mass of egg white protein after the ferulic acid solution and the egg white protein solution are mixed in S2.

[0012] Preferably, the pH is adjusted to 9.0, and then adjusted to 7.0 after 12 hours in S2.

[0013] Preferably, the ultrasonic treatment in S2 is performed by using an ultrasonic wave disruptor with a treatment power of 400 W for 30 min.

[0014] Preferably, the dialysis treatment in S2 is performed by using a dialysis bag with a molecular weight cut-off of 7 kDa.

[0015] Preferably, the mass / volume ratio of sodium alginate to water in the sodium alginate solution of S3 is 1:70, and the mass / volume ratio of corn alcohol-soluble protein to 80% ethanol solution in the corn alcohol-soluble protein solution is 1:30.

[0016] A food source-based active coating for preventing dry consumption under ultra-low temperature conditions, the coating comprising an inner layer composite coating solution and an outer layer composite coating solution, the coating being prepared by the above method.

[0017] Preferably, the spraying of the coating is performed by adding the inner layer composite coating solution or the outer layer composite coating solution into a high-pressure atomizing spray gun, respectively, and then spraying, first spraying the inner layer composite coating solution, and then spraying the outer layer composite coating solution after the inner layer coating is dried.

[0018] The above-mentioned food source-based active coating for preventing dry consumption under ultra-low temperature conditions is applied to fresh-keeping food.

[0019] Advantages

[0020] 1. The present application combines double-layer coating, inhibits free radical oxidation generated by freezing through the inner layer antioxidant, effectively locks water and blocks external oxygen penetration through the synergistic effect of the outer layer high-barrier structure, significantly improves the freezing preservation effect of food, and the raw materials used are natural and safe, the preparation method is reasonable, and has good practical application value.

[0021] 2、The outer coating layer of the present application adopts high hydrophobicity zein and adds sodium alginate with high viscosity and good film-forming property, to form a structure with high viscosity and high barrier property, which can efficiently lock water and block external oxygen permeation.

[0022] 3、The inner coating layer of the present application selects ferulic acid as an antioxidant, which is a natural polyphenol with good antioxidant effect, and the ferulic acid is covalently combined with egg white protein through an ultrasonic-assisted alkali treatment method to prepare a stable egg white protein-ferulic acid covalent compound, and the antioxidant in the inner coating layer can effectively inhibit the free radical oxidation generated in the food storage process. Moreover, the natural polyphenol ferulic acid added to the egg white protein can be uniformly distributed in the inner edible coating layer, which not only improves the surface hydrophobicity, viscosity, thermal stability and other performance indicators of the coating layer, but also greatly increases the antioxidant property of the coating layer from 15% to 87%, significantly enhances the antioxidant capacity of the coating layer, and highlights the great potential of the coating layer as a food active packaging.

[0023] 4、The present application uses an ultrasonic cell disrupter to treat the compound solution, and the ultrasonic treatment significantly reduces the particle size of the egg white protein-ferulic acid compound, makes the coating more delicate, and also makes the combination of egg white protein and ferulic acid more compact, increases the solubility of egg white protein, and significantly reduces insoluble substances; and the compound system is modified by using ultrasonic-assisted alkali treatment technology, and the synergistic effect of ultrasonic and alkali treatment effectively enhances the molecular stability of ferulic acid in a low-temperature environment, significantly improves the encapsulation rate of active ingredients by regulating the microstructure of the compound, and the method not only maintains the biological activity of ferulic acid in a super-low temperature environment of -(20~50)℃, but also realizes the slow-release property by constructing an ordered protein polysaccharide cross-linking network, and the cavitation effect generated by ultrasonic waves promotes the uniform dispersion of the compound particles, improves the storage stability of the controlled-release system, and further enhances the performance of the coating layer and the practicability and potential of the coating layer as a food active packaging. DETAILED DESCRIPTION

[0024] I. Experimental method

[0025] 1. Performance analysis of the composite coating layer

[0026] (1) DPPH and ABTS free radical scavenging rate

[0027] A DPPH (1,1-diphenyl-2-trinitrobenzene hydrazine) solution with a concentration of 0.8 mmol / L (0.315 mg / mL) is prepared using ethanol. The sample solution is diluted 5 times with deionized water, 2 mL of the diluted sample solution is taken, 2 mL of DPPH solution is added and mixed, and placed in the dark, and after 30 min of reaction at room temperature, the absorbance at 517 nm is measured, and the blank uses ethanol instead of the sample solution.

[0028] DPPH free radical scavenging rate (%) = x 100%

[0029] ABTS solution and 1 mg / mL of potassium persulfate solution were prepared with distilled water, mixed in equal volume, and placed in the refrigerator for 16 h. 3 mL of the mixed solution was diluted with anhydrous ethanol to 100 mL to prepare a working solution. The diluted sample solution (0.5 mg / mL) was mixed with the working solution at a ratio of 1:3 (v / v), reacted in the dark for 1 h, and the absorbance was measured at 734 nm.

[0030] ABTS radical scavenging rate (%) = (A0- Asample) / A0x 100%

[0031] (2) Ferulic acid encapsulation rate.

[0032] A certain amount of ferulic acid was dissolved in 70% ethanol and diluted to the required concentration. The absorbance value was measured at 280 nm using a UV spectrophotometer, and a standard curve of ferulic acid was prepared. The complex solution was mixed with anhydrous ethanol at a ratio of 1:4, centrifuged at 8000 r / min, and the supernatant was diluted 20 times with anhydrous ethanol. The absorbance value was measured at 280 nm using a UV spectrophotometer. According to the prepared standard curve of ferulic acid and the dilution factor, the content of ferulic acid was calculated. The encapsulation rate calculation formula is as follows:

[0033] Encapsulation efficiency (EE) = (C0- Cs) / C0x 100%

[0034] (3) Rheological analysis.

[0035] The rheological properties of the composite coating solution were tested using a HAAKE MARS 60 rotational rheometer. In the test, 3 mL of sample was added to a 60 mm flat plate with a gap of 1.0 mm. The change in viscosity of the system under different shear rates was studied in the range of shear rate from 0.1 s-1 to 100 s-1.

[0036] (4) Particle size.

[0037] The average particle size was measured using a Zetasizer Nano ZS90 nanoparticle size analyzer. The sample was diluted 100 times with deionized water before measurement, and the particle size was measured three times at room temperature with an equilibration time of 10 s.

[0038] 2. Application of composite coating in food frozen storage.

[0039] (1) Determination of dry loss rate.

[0040] ​​The food in the test was weighed by using the differential method, and 3 samples were taken for weight determination in each group. The weight was weighed by using an electronic scale before and after storage, and the average weight (g) of each group of samples was recorded every day. The weight loss rate was calculated according to the following formula:

[0041] Dry loss rate =

[0042] In the formula, m0 is the mass of the food before storage (g), and m1 is the mass of the food after storage (g).

[0043] (2) Determination of the oxidation degree of food.

[0044] The sample was ground, sieved, and placed in a 50 mL centrifuge tube. 15 mL of petroleum ether was added. The sample was treated with ultrasonic waves for ten minutes in an ultrasonic cleaner to release the oil. The sample was centrifuged at 4000 rpm for 10 minutes. The supernatant was collected, and the precipitate was washed with 3 mL of petroleum ether. The centrifugation was repeated, and the supernatants were combined. The supernatant was added to a pre-weighed triangular flask, and the petroleum ether was evaporated under the condition of light protection in a fume hood at 40 degrees. The oil was obtained, and the mass of the oil was weighed again

[0045] 5 mL of a mixture of chloroform and glacial acetic acid was added, 1 mL of saturated KI solution was added, and the reaction was carried out in the dark for 5 minutes. 1 mL of starch indicator was added, and the solution was titrated with 2 mmol / L of NA2S2O3 standard solution until it was colorless. The amount of NA2S2O3 standard solution used was calculated.

[0046]

[0047] X1: Peroxide value, in grams per 100 grams (g / 100g);

[0048] V: Volume of sodium thiosulfate standard titration solution consumed by the sample, in milliliters (mL);

[0049] V0: Volume of sodium thiosulfate standard titration solution consumed by the blank test, in milliliters (mL);

[0050] C: Concentration of sodium thiosulfate standard titration solution, in moles per liter (mol / L);

[0051] 0.1269: Mass of iodine equivalent to 1.00 mL of sodium thiosulfate standard titration solution with a concentration (C) of 1.000 mol / L, in grams per millimole (g / mmol);

[0052] M: Mass of the sample, in grams (g);

[0053] 100: Conversion factor for 100 g of sample.

[0054] Example 1:

[0055] 1. Preparation of egg white protein-ferrulic acid inner layer composite coating:

[0056] (1) Dissolution of egg white protein and ferrulic acid: 2.0 g of egg white protein was weighed and added to 95 mL of water to prepare an egg white protein solution by stirring at room temperature for 30 min. 40 mg of ferrulic acid was dissolved in 5 mL of 80% ethanol solution to prepare a ferrulic acid solution by stirring at room temperature for 30 min;

[0057] (2) pH adjustment: the ferrulic acid solution was added to the egg white protein solution to make the final content of ferrulic acid 2% of the mass of egg white protein, and the pH was adjusted to 9.0 with 1 mol / L NaOH solution. The mixture was left to stand for 12 hours, and then the pH was adjusted to 7.0 again to obtain a mixed solution;

[0058] (3) Ultrasonic treatment: the mixed solution was treated with an ultrasonic cell disruptor, and the ultrasonic parameters were set as follows: ultrasonic power 400 W, ultrasonic time 30 min (ultrasonic 3 s off 3 s);

[0059] (4) Centrifugal treatment: the solution was treated by centrifugation, and the supernatant was taken, and the centrifugal parameters were set as follows: 8000 rpm, 15 min;

[0060] (5) Dialysis treatment: the solution was treated by dialysis with a dialysis bag (molecular weight cut-off 7 kDa) to remove covalently bound ferrulic acid to obtain an inner layer composite coating solution.

[0061] 2. Preparation of corn alcohol soluble protein and sodium alginate outer layer composite coating:

[0062] (1) Dissolution of corn alcohol soluble protein and sodium alginate: 1.0 g of corn alcohol soluble protein was dissolved in 30 mL of 80% ethanol to prepare a corn alcohol soluble protein solution by stirring at room temperature for 30 min. 1.0 g of sodium alginate was added to 70 mL of water to prepare a sodium alginate solution by stirring at room temperature for 30 min;

[0063] (2) Preparation of corn alcohol soluble protein and sodium alginate composite coating: the corn alcohol soluble protein solution was slowly added to the sodium alginate solution to obtain a composite. 2.0 g of glycerol was weighed and added to the composite solution, and it was fully dissolved by stirring at 40°C water bath for 15 min to obtain an outer layer composite coating solution;

[0064] 3. Coating application.

[0065] The inner layer composite coating solution or the outer layer composite coating solution prepared above was added into a high-pressure atomizing spray gun, respectively, to spray and coat cashew, almond, freeze-dried eggplant, and freeze-dried jackfruit, first to spray the inner layer composite coating solution, and then to spray the outer layer composite coating solution after the inner layer coating was dried. The food coated was stored in -20 to -50°C.

[0066] Example 2:

[0067] 1. Preparation of egg white protein-ferulic acid inner layer composite coating:

[0068] (1) Dissolution of egg white protein and ferulic acid: 2.0 g of egg white protein was weighed and added into 95 mL of water to prepare an egg white protein solution by stirring at room temperature for 30 min. 60 mg of ferulic acid was weighed and dissolved in 5 mL of 80% ethanol solution to prepare a ferulic acid solution by stirring at room temperature for 30 min.

[0069] (2) pH adjustment: the ferulic acid solution was added to the egg white protein solution to make the final content of ferulic acid 4% of the mass of egg white protein, and the pH was adjusted to 9.0 with 1 mol / L NaOH solution. The mixture was left to stand for 12 hours, and then the pH was adjusted to 7.0 again to obtain a mixed solution.

[0070] (3) Ultrasonic treatment: the mixed solution was treated with an ultrasonic cell disruptor, and the ultrasonic parameters were set as follows: ultrasonic power 400 W, ultrasonic time 30 min (ultrasonic 3 s off 3 s).

[0071] (4) Centrifugal treatment: the solution was treated by centrifugation, and the supernatant was taken, and the centrifugal parameters were set as follows: 8000 rpm, 15 min.

[0072] (5) Dialysis treatment: the solution was treated by dialysis with a dialysis bag (7 kDa molecular weight cut-off) to remove covalently bound ferulic acid to obtain an inner layer composite coating solution.

[0073] 2. Preparation of corn alcohol-soluble protein and sodium alginate outer layer composite coating:

[0074] (1) Dissolution of corn alcohol-soluble protein and sodium alginate: 1.0 g of corn alcohol-soluble protein was dissolved in 30 mL of 80% ethanol to prepare a corn alcohol-soluble protein solution by stirring at room temperature for 30 min. 1.0 g of sodium alginate was added into 70 mL of water to prepare a sodium alginate solution by stirring at room temperature for 30 min.

[0075] (2) Preparation of corn alcohol-soluble protein and sodium alginate composite coating: the corn alcohol-soluble protein solution was slowly added to the sodium alginate solution to obtain a complex. 2.0 g of glycerol was weighed and added to the complex solution, and the solution was stirred in a 40°C water bath for 15 min to fully dissolve to obtain an outer layer composite coating solution.

[0076] 3. Coating applications

[0077] The inner layer composite coating solution or the outer layer composite coating solution prepared above was added into a high-pressure atomizing spray gun, respectively, to spray and coat cashews, almonds, freeze-dried eggplants, and freeze-dried jackfruits. The inner layer composite coating solution was sprayed first, and then the outer layer composite coating solution was sprayed after the inner layer coating was dried. The food coated with the coating was stored in -20 to -50°C.

[0078] Example 3:

[0079] 1. Preparation of egg white protein-ferulic acid inner layer composite coating:

[0080] (1) Dissolution of egg white protein and ferulic acid: 2.0 g of egg white protein was weighed and added to 95 mL of water to prepare an egg white protein solution by stirring at room temperature for 30 min. 80 mg of ferulic acid was dissolved in 5 mL of 80% ethanol solution by stirring at room temperature for 30 min to prepare a ferulic acid solution;

[0081] (2) pH adjustment: the ferulic acid solution was added to the egg white protein solution to make the final content of ferulic acid 6% of the mass of egg white protein, and the pH was adjusted to 9.0 with 1 mol / L NaOH solution. The mixture was left to stand for 12 hours, and then the pH was adjusted to 7.0 again to obtain a mixed solution;

[0082] (3) Ultrasonic treatment: the mixed solution was treated with an ultrasonic cell disruptor, and the ultrasonic parameters were set as follows: ultrasonic power 400 W, ultrasonic time 30 min (ultrasonic 3 s off 3 s);

[0083] (4) Centrifugal treatment: the solution was treated by centrifugation, and the supernatant was taken, and the centrifugal parameters were set as follows: 8000 rpm, 15 min;

[0084] (5) Dialysis treatment: the solution was treated by dialysis using a dialysis bag (molecular weight cut-off 7 kDa) to remove covalently bound ferulic acid, and an inner layer composite coating solution was obtained;

[0085] 2. Preparation of corn alcohol-soluble protein and sodium alginate outer layer composite coating:

[0086] (1) Dissolution of corn alcohol-soluble protein and sodium alginate: 1.0 g of corn alcohol-soluble protein was dissolved in 30 mL of 80% ethanol, and the solution was stirred at room temperature for 30 min to prepare a corn alcohol-soluble protein solution. 1.0 g of sodium alginate was added to 70 mL of water, and the solution was stirred at room temperature for 30 min to prepare a sodium alginate solution;

[0087] (2) Preparation of the zein and sodium alginate composite coating: The zein solution was slowly added to the sodium alginate solution to obtain a composite. 2.0 g of glycerol was weighed and added to the composite solution, which was stirred in a water bath at 40°C for 15 min to fully dissolve, to obtain an outer composite coating solution;

[0088] 3. Coating application.

[0089] The inner composite coating solution or the outer composite coating solution prepared in the above was added to a high-pressure atomizing spray gun, respectively, to spray the coatings on cashews, almonds, freeze-dried eggplants, and freeze-dried jackfruits. The inner composite coating solution was sprayed first, and then the outer composite coating solution was sprayed after the inner coating was dried. The food sprayed with the coating was stored in a freezer at -20 to -50°C.

[0090] Comparative Example 1.

[0091] 1. Preparation of the egg white protein-ferulic acid inner composite coating:

[0092] (1) Dissolution of egg white protein and ferulic acid: 2.0 g of egg white protein was weighed and added to 95 mL of water, which was stirred at room temperature for 30 min to prepare an egg white protein solution. 60 mg of ferulic acid was dissolved in 5 mL of 80% ethanol solution, which was stirred at room temperature for 30 min to prepare a ferulic acid solution;

[0093] (2) pH adjustment: The ferulic acid solution was added to the egg white protein solution to give a final ferulic acid content of 4% of the mass of the egg white protein. The pH was adjusted to 9.0 with a 1 mol / L NaOH solution, and the mixture was left to stand for 12 hours. The pH was then adjusted to 7.0 again to obtain a mixed solution;

[0094] (3) Ultrasonic treatment: The mixed solution was treated with an ultrasonic cell disruptor, with the ultrasonic parameters set as follows: ultrasonic power 400 W, ultrasonic time 30 min (3 s on and 3 s off);

[0095] (4) Centrifugal treatment: The solution was treated by centrifugation, and the supernatant was taken, with the centrifugal parameters set as follows: 8000 rpm, 15 min;

[0096] (5) Dialysis treatment: The solution was treated by dialysis using a dialysis bag (7 kDa molecular weight cut-off) to remove covalently bound ferulic acid, to obtain an inner composite coating solution;

[0097] 2. Coating application: The coating solution prepared in the above was added to a high-pressure atomizing spray gun, and the coating solution was sprayed on cashews, almonds, freeze-dried eggplants, and freeze-dried jackfruits. The food sprayed with the coating was stored in a freezer at -20 to -50°C.

[0098] Comparative Example 2.

[0099] 1. Preparation of zein and sodium alginate outer layer composite coating:

[0100] (1) Dissolution of zein and sodium alginate: a certain amount of zein was dissolved in 80% ethanol, stirred at room temperature for 30 min to prepare a zein solution. A certain amount of sodium alginate was added to water, stirred at room temperature for 30 min to prepare a sodium alginate solution;

[0101] (2) Preparation of zein and sodium alginate composite coating: slowly add the zein solution to the sodium alginate solution, weigh a certain amount of glycerol, add it to the composite solution, stir in a 40°C water bath for 15 min to fully dissolve, and obtain an outer layer composite coating solution;

[0102] 2. Coating application: add the coating solution prepared above to a high-pressure atomizing spray gun, and spray the coating on cashews, almonds, freeze-dried zucchini, and freeze-dried jackfruit. Place the coated food in -20~-50°C for frozen storage.

[0103] Comparative Example 3.

[0104] Place the untreated cashews, almonds, freeze-dried zucchini, and freeze-dried jackfruit in -20~-50°C for frozen storage.

[0105] The coatings of Examples 1-3 and Comparative Example 1 were analyzed for DPPH ABTS radical scavenging rate, ferulic acid encapsulation rate, apparent viscosity, and particle size. The results are shown in Table 1. According to Table 1, Examples 1-3 are significantly better than Comparative Examples 1 and 2 in ABTS radical scavenging rate (%), ferulic acid encapsulation rate (%), and apparent viscosity (Pa·s), with Example 3 improving from 15% to 87% relative to Comparative Example 2. Examples 2-3 are significantly better than Comparative Examples 1 and 2 in DPPH radical scavenging rate (%), with Example 3 improving from 10% to 76% relative to Comparative Example 2. The particle sizes of Examples 1-3 are smaller than that of Comparative Example 1.

[0106] Table 1

[0107]

[0108] Note: 1. Each group of experiments was conducted in triplicate, and each value is the average of three data; 2. In the same row of data, if several data are followed by the same letter, it means that there is no significant difference between the several data, and if several data are followed by different letters, it means that there is a significant difference between the several data.

[0109] The frozen storage experiment of cashews and almonds coated with the composite coating of Examples 1-3 and Control Examples 1-3 was conducted for 180 days, and sampling was performed every 30 days, and index determination and analysis were performed, and the results are shown in Tables 2 and 2 (The six data in the dry loss rate experiment are the experimental results of storage for 30, 60, 90, 120, 150, and 180 days, respectively; The seven data in the peroxide value experiment are the experimental results of storage for 0, 30, 60, 90, 120, 150, and 180 days, respectively, in which the data of the 0th day is represented as POV0, and the data of the 180th day is represented as POV180). 180 ).

[0110] Table 2

[0111]

[0112] According to Table 2, in the frozen storage experiment of cashews, the dry loss rate of the coated cashews of the three experimental groups was about 6.8-7.8% at 180 days, and the dry loss rate of the coated cashews of the control group was about 7.3-14% at 180 days, which can be determined that the dry loss rate of the coated cashews of the spraying experimental group was significantly reduced. According to the peroxide value data in Table 2, the calculation ((POV180-POV0) / POV0) 100) % was performed, and the peroxide value increase rate of the coated cashews of the three experimental groups was less than 10% at 180 days, and the peroxide value increase rate of the coated cashews of the control group was as high as 30% at 180 days. 180 -POV0) / POV 0* 100) %.

[0113] Table 3

[0114]

[0115] According to Table 3, in the frozen storage experiment of almonds, the dry loss rate of the coated almonds of the three spraying experimental groups was less than 8% at 180 days, and the dry loss rate of the coated almonds of the control group was higher than 10% at 180 days, which can be determined that the dry loss rate of the coated almonds of the spraying experimental group was significantly reduced. According to the peroxide value data in Table 3, the calculation ((POV180-POV0) / POV0) 100) % was performed, and the peroxide value increase rate of the coated almonds of the three experimental groups was less than 13% at 180 days, and the peroxide value increase rate of the coated almonds of the control group was as high as 53% at 180 days. 180 -POV0) / POV 0* 100) %.

Claims

1. A method for the preparation of a dry-feed food-grade active coating against super-low temperature conditions, characterized by, The preparation method is as follows: S1: mixing egg white protein and water to prepare an egg white protein solution; dissolving ferulic acid in an 80% ethanol solution to prepare a ferulic acid solution; S2: mixing the ferulic acid solution and the egg white protein solution, adjusting the pH with a NaOH solution to obtain a mixed solution, and performing ultrasonic treatment on the solution with an ultrasonic cell disruptor; then performing centrifugation and dialysis treatment to obtain an inner layer composite coating solution; S3: dissolving zein in an 80% ethanol solution to obtain a zein solution; adding sodium alginate to water to obtain a sodium alginate solution; S4: adding the zein solution to the sodium alginate solution, and adding glycerol, uniformly stirring in a water bath to obtain an outer layer composite coating solution.

2. The method of claim 1, wherein, The mass / volume ratio (g / mL) of egg white protein to water in the egg white protein solution in S1 is 2:95, and the mass / volume ratio (mg / mL) of ferulic acid to the 80% ethanol solution in the ferulic acid solution is 8-16:

1.

3. The method of claim 1, wherein, After mixing the ferulic acid solution and the egg white protein solution in S2, the ferulic acid accounts for 2%-6% of the mass of the egg white protein.

4. The method of claim 1, wherein, In S2, the pH is adjusted to 9.0, and after 12 hours, the pH is adjusted to 7.

0.

5. The method of claim 1, wherein, In S2, the ultrasonic treatment is performed with an ultrasonic disruptor at a power of 400 W for 30 min.

6. The method of claim 1, wherein, In S2, the dialysis treatment is performed with a dialysis bag with a molecular weight cut-off of 7 kDa.

7. The method of claim 1, wherein, In S3, the mass / volume ratio of sodium alginate to water in the sodium alginate solution is 1:70, and the mass / volume ratio of zein to the 80% ethanol solution in the zein solution is 1:

30.

8. A food source based active coating against desiccation under ultra-low temperature conditions, characterized by, The coating is prepared by the preparation method of the coating of any one of claims 1-7.

9. The coating of claim 8, wherein, The spraying of the coating is performed by adding the inner layer composite coating solution or the outer layer composite coating solution into a high-pressure atomizing spray gun, respectively, and then performing spraying. First, the inner layer composite coating solution is sprayed, and then the outer layer composite coating solution is sprayed after the inner layer coating is dried.

10. The application of the coating for preventing dry consumption of food source activity under ultra-low temperature conditions in fresh-keeping food according to claim 8.

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