Edible coating film capable of prolonging shelf life of nuts

Abstract

The invention discloses an edible coating film capable of prolonging the shelf life of nuts, and belongs to the field of edible films and food oxidation resistance. The coating liquid comprises the following components: carboxymethyl cellulose, Arabic gum, glycerol, phospholipid, TBHQ and VC. The film-coated peeled walnut kernels which are dried and packaged in vacuum are placed in a drying oven at 60 DEG C to be subjected to accelerated oxidation for 30 days, an optimal combined film coating formula is obtained, and finally, a shelf life model of the film-coated peeled walnut kernels with the optimal formula is established. The prepared composite coating film is high in adhesion and permeability and good in water resistance and mechanical performance, the coating film method is simple, convenient and effective, the shelf life of the peeled walnut kernels is obviously prolonged, and the peeled walnut kernels can be placed for about 12 months under the normal-temperature vacuum condition.

Description

Technical Field

[0001] The invention relates to an edible coating film for extending the shelf life of nuts, and belongs to the field of edible films and food antioxidants. Background Art

[0002] Walnuts and other nuts are rich in unsaturated fatty acids, such as oleic acid, linoleic acid, linolenic acid and arachidonic acid, with a content of more than 90%. They also contain vitamins and polyphenol antioxidants, which can resist aging, purify blood, lower cholesterol, and prevent cardiovascular diseases. The endocarp of walnut kernels is rich in "tannins", which tastes bitter when eaten directly, and is easy to form precipitation with protein, which is not conducive to subsequent deep processing. During storage, as water is lost, the endocarp undergoes a certain degree of browning, and the sensory quality of walnut kernels is reduced, affecting the appearance of subsequent products and reducing economic value.

[0003] Peeled walnut kernels without the endocarp are more popular among consumers in the market. However, since 90% of the polyphenols in walnuts are concentrated in the endocarp, the peeled walnut kernels lack the protective effect of the endocarp, and the oil is more easily oxidized, and the shelf life is shorter. During storage, walnuts mainly undergo oil free radical chain reactions and hydrolysis oxidation processes, and eventually generate small molecules such as aldehydes, ketones, and acids, which produce rancid odors and have adverse effects on walnut kernel products and human health. Therefore, the antioxidant treatment of peeled walnut kernels has important research significance for product quality, economic value and consumer health.

[0004] The membrane liquid can be used as a carrier for additives such as antioxidants, thickeners, and emulsifiers. It can reduce fat oxidation and the loss of volatile flavor substances by blocking moisture and oxygen to maintain food quality, extend shelf life, and save packaging materials. The antioxidant and mechanical properties of a single coating material need to be improved. In actual operation, a composite coating is used to improve its performance and extend shelf life. At present, domestic and foreign studies mostly use soaking to slow down the oxidative rancidity of walnut kernels with skin. The rancidity law of walnut kernel quality is similar to the first-order kinetic reaction. There are few studies on the antioxidant coating and shelf life model of peeled walnut kernels. Nuts contain high levels of oil, especially unsaturated fatty acids, which are easily affected by oxygen, light, and temperature to undergo oxidation reactions.

[0005] The exposure of oil on the surface of nuts and the porous structure of nuts easily absorb oxygen and accelerate the oxidation process. This oxidation can cause nuts to deteriorate, produce odors and lose nutrients. Therefore, the coating needs to not only form a good barrier to prevent the penetration of oxygen, moisture and light, but also maintain the texture and flavor of the nuts, which places high demands on the formulation design of the coating.

[0006] Conventional edible coating technology is mostly used for fruit and vegetable preservation. Unlike vegetables, nuts have a high oil content, and the coating must have strong antioxidant properties to protect the oil on the surface of nuts, while avoiding adverse reactions between the coating and the oil. Patent CN111869810A discloses a method for preparing a natural antioxidant, which mentions that compared with synthetic antioxidants, natural antioxidants are more and more widely used, but the use of natural antioxidants alone on the surface of food is prone to decreased utilization and easy to be oxidized by air. Among the antioxidants, BHA (butylated hydroxyanisole), BHT (butylated hydroxytoluene), PG (propyl gallate), TBHQ (tert-butylhydroquinone) and tocopherol are five widely used antioxidants in the world. They can be used alone or in combination with acidic synergists such as citric acid and ascorbic acid, which are more stable and can meet the needs of most food products. However, the surface of nuts is harder and smoother than most fruits and vegetables, and traditional fruit and vegetable coatings may be difficult to form effective adhesion on such surfaces. In addition, the moisture content of nuts is lower than that of vegetables, and traditional coatings may not play an ideal moisturizing role on nuts, because the main preservation requirement of nuts is anti-oxidation rather than water retention. The coating of nuts needs to maintain the unique flavor and crispness of nuts. Too thick or inappropriate coatings will affect consumers' eating experience. Patent CN109957148A discloses the use of sodium carboxymethyl cellulose, gum arabic, glycerin, and phospholipids to prepare edible films, but the purpose of this patent is to solve the problem of the convenience of carrying ingredients such as lutein, and the application field focuses more on food processing form innovation rather than food preservation.

[0007] Therefore, studying a coating method to delay the rancidity of peeled walnut kernels and predicting the shelf life through a kinetic model are of great significance to improving the quality and economic value of walnuts and promoting rural economic development. Summary of the invention

[0008] In order to solve the above problems, the present invention prepares an edible coating film based on sodium carboxymethyl cellulose, gum arabic, glycerol, phospholipids, tertiary butyl hydroquinone and vitamin C. The edible coating film prepared by the present invention is used to wrap nuts, has the effects of delaying the rancidity of nuts, extending the shelf life, and anti-oxidation, and is of great significance to improving the quality and economic value of walnuts and promoting the development of rural economy.

[0009] The first object of the present invention is to provide a method for preparing an edible coating, comprising the steps of:

[0010] Mixing sodium carboxymethyl cellulose, gum arabic, glycerin, phospholipids, tert-butylhydroquinone (TBHQ) and vitamin C to prepare a coating liquid, casting into a film, and preparing an edible coating film;

[0011] Alternatively, the food is immersed in the coating liquid to prepare an edible coating on the surface of the food.

[0012] In one embodiment, the amounts (%) in the present invention are all mass fractions unless otherwise specified.

[0013] In one embodiment, the coating solution contains, by mass fraction, 0.05-3.00% sodium carboxymethyl cellulose, 0.01-1.00% gum arabic, 1.00-3.00% glycerol, 0.01-1.00% phospholipids, 0.03-0.08% tert-butylhydroquinone and 0.10-0.20% vitamin C.

[0014] In one embodiment, walnut seed coat extract may be used in place of tert-butylhydroquinone.

[0015] In one embodiment, when sodium carboxymethyl cellulose, gum arabic, glycerin, phospholipids, tert-butylhydroquinone and vitamin C are mixed, they are stirred at a high speed of 2000 rpm until they are completely dissolved, and ultrasonic degassing is performed.

[0016] In one embodiment, the casting film is to pour the coating liquid into a container, and vacuum dry it at 50-90° C. for 8-10 hours or dry it at normal pressure for 10-20 hours.

[0017] In one embodiment, soaking the food in the coating liquid is soaking the food in the coating liquid for 1-10 minutes.

[0018] The second object of the present invention is to provide an edible coating prepared by any of the above methods.

[0019] The third object of the present invention is to provide a packaging material containing the above-mentioned edible coating film.

[0020] In one embodiment, the packaging material is used to package fruits, vegetables and fresh food, which can extend the shelf life of the fruits, vegetables and fresh food.

[0021] A fourth object of the present invention is to provide the use of the above-mentioned edible coating in the fields of food, medicine, agricultural products or textiles.

[0022] A fifth object of the present invention is to provide a method for extending the shelf life of nuts, comprising wrapping the nuts with any of the above-mentioned films; or, soaking the nuts in a coating liquid for 1-10 minutes.

[0023] In one embodiment, the method for preparing the coating liquid comprises mixing sodium carboxymethyl cellulose, gum arabic, glycerol, phospholipids, tert-butylhydroquinone and vitamin C to prepare the coating liquid;

[0024] In one embodiment, the coating solution contains, by mass fraction, 0.05-3.00% sodium carboxymethyl cellulose, 0.01-1.00% gum arabic, 1.00-3.00% glycerol, 0.01-1.00% phospholipids, 0.03-0.08% tert-butylhydroquinone and 0.10-0.20% vitamin C.

[0025] In one embodiment, when sodium carboxymethyl cellulose, gum arabic, glycerin, phospholipids, tert-butylhydroquinone and vitamin C are mixed, they are stirred at a high speed of 2000 rpm until they are completely dissolved, and ultrasonic degassing is performed.

[0026] Beneficial effects of the present invention

[0027] The present invention prepares an edible coating film based on sodium carboxymethyl cellulose, gum arabic, glycerol, phospholipids, tertiary butyl hydroquinone and vitamin C. The edible coating film prepared by the present invention is used for wrapping nuts, has the effects of delaying the rancidity of nuts, extending the shelf life and anti-oxidation, and is of great significance to improving the quality and economic value of walnuts and promoting the development of rural economy.

[0028] The composite coating prepared by the invention has high adhesion and permeability, and good water-blocking and mechanical properties. The coating method is simple, convenient and effective, and can significantly delay the shelf life of the peeled walnut kernels, which can be stored for about 12 months under normal temperature and vacuum conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Effects of different film-forming substrate (CMC, NaAlg) contents on edible film properties: (a) adhesion index; (b) water vapor permeability WVP; (c) transparency T; (d) tensile strength TS and elongation E.

[0030] Figure 2 Effects of different gum arabic contents on the properties of edible films: (a) adhesion index; (b) water vapor permeability WVP; (c) transparency T; (d) tensile strength TS and elongation E.

[0031] Figure 3 Effects of different glycerol contents on the properties of edible films: (a) adhesion index; (b) water vapor permeability WVP; (c) transparency T; (d) tensile strength TS and elongation E.

[0032] Figure 4 Effects of different phospholipid contents on the properties of edible films: (a) adhesion index; (b) water vapor permeability WVP; (c) transparency T; (d) tensile strength TS and elongation E.

[0033] Figure 5The antioxidant activities of TBHQ, seed coat extract and rosemary extract are (a): DPPH scavenging rate; (b): ABTS scavenging rate; (c): FRAP value.

[0034] Figure 6 The actual value, theoretical value and synergy of DPPH scavenging rate are (a): walnut seed coat extract combined with citric acid / vitamin C; (b): TBHQ combined with citric acid / vitamin C.

[0035] Figure 7 The actual value, theoretical value and synergy of ABTS clearance rate (a): walnut seed coat extract combined with citric acid / vitamin C; (b): TBHQ combined with citric acid / vitamin C.

[0036] Figure 8 The first-order kinetic model of oxidation of coated and peeled walnut kernels: (a) acid value; (b) peroxide value.

[0037] Fig. 9 Acid value and peroxide value of coated macadamia and hazelnut after accelerated oxidation for 30 days (a): acid value; (b): peroxide value. DETAILED DESCRIPTION

[0038] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explaining the present invention and are not used to limit the present invention.

[0039] The instruments and materials involved in the present invention are:

[0040] Vacuum packaging machine; Electric blast drying oven, DZF-6050 vacuum drying oven, Shanghai Boxun Industrial Co., Ltd.;

[0041] TA.XTPlus physical property analyzer, SMS company, UK;

[0042] ZDJ-5B automatic potentiometric titrator, Shanghai Leici Electrochemical Instrument Co., Ltd.;

[0043] The peeled walnut kernels were vacuum dried at 50°C for 10-12 h until the moisture content was less than 3.00%, and were purchased from Hebei Huadai Agricultural Technology Co., Ltd.;

[0044] Sodium carboxymethyl cellulose (CMC), sodium alginate (NaAlg), starch, polyethanol, gum arabic, VC, and phospholipids were all food grade and purchased from Henan Ren'an Biotechnology Co., Ltd.;

[0045] TBHQ was purchased from Henan Ren'an Biotechnology Co., Ltd.;

[0046] Walnuts were purchased from Hebei Huadai Agricultural Technology Co., Ltd., and walnut seed coat extracts were obtained by using 70% ethanol (solid-liquid ratio 1:20), 50°C ultrasonic extraction for 15 min, and extraction for 4 times;

[0047] Rosemary extract was purchased from Henan Gaobao Industrial Co., Ltd.

[0048] Example 1: Preparation of edible coating

[0049] 1. Preparation of coating solution

[0050] The images of different amounts of sodium carboxymethyl cellulose, sodium alginate, gum arabic, glycerol and phospholipids were tested for their effects on film-forming properties. The preparation methods and groupings are as follows:

[0051] Group 1: Sodium carboxymethyl cellulose (CMC) / sodium alginate (NaAlg) was used as the film-forming matrix in different addition amounts (mass fraction, 0.50%, 0.75%, 1.00%, 1.25%, 1.50%), and 0.50% gum arabic, 2.00% glycerol, and 0.10% phospholipids were added and dissolved in boiling water.

[0052] Group 2: 1.50% sodium carboxymethyl cellulose was used as the film-forming matrix, and different amounts (mass fraction, 0.00%, 0.25%, 0.50%, 0.75%, 1.00%) of gum arabic, 2.00% glycerol, and 0.10% phospholipids were dissolved in boiling water.

[0053] Group 3: 1.50% sodium carboxymethyl cellulose was used as the film-forming matrix, and 0.50% gum arabic, different amounts of glycerol (mass fraction, 1.00%, 1.50%, 2.00%, 2.50%, 3.00%), and 0.10% phospholipids were dissolved in boiling water.

[0054] Group 4: 1.50% sodium carboxymethyl cellulose was used as the film-forming matrix, and 0.50% gum arabic, 2.00% glycerol, and different amounts (mass fraction, 0.00%, 0.05%, 0.10%, 0.15%, 0.20%) of phospholipids were dissolved in boiling water.

[0055] 2. Preparation of edible film

[0056] Take the coating liquid prepared in 1, add 0.01% TBHQ (tert-butylhydroquinone) and 0.02% VC respectively, stir at 2000 rpm, degas by ultrasonication, pour 40 g into a plastic culture dish, and dry in an oven at 60° C. for 10 h to prepare an edible film.

[0057] The adhesion index, water vapor permeability, transparency and mechanical properties of edible films are tested to determine the optimal content in the coating solution.

[0058] The results of the effects of different film-forming substrate (CMC / NaAlg) contents on the properties of edible films are shown in Figure 2. Figure 1 As shown in the figure, when the concentration of the film-forming matrix increases, the adhesion index of the edible film increases, the water vapor transmission rate first decreases and then increases, the transparency decreases, the tensile strength increases, and the elongation decreases. In general, the adhesion index of CMC is higher than that of NaAlg. When the substrate concentration is 1.00%, the WVP of CMC is the lowest. When it exceeds 1.00%, the transparency of CMC decreases, the tensile strength is inversely proportional to the elongation, and the flexibility of CMC film is better than that of NaAlg film, so 1.00% CMC is selected as the film-forming substrate.

[0059] Effects of different gum arabic contents on the properties of edible films Figure 2 As shown, gum arabic is an amphiphilic molecule. With the increase of the added amount, the adhesion index increases, the effect on WVP is small, the transparency changes, the tensile strength increases first and then decreases, and the elongation is the opposite. When the addition amount of gum arabic is 0.75%, the adhesion index of the film is as high as 83.06%, the permeability is the best, the mechanical strength is good, and it has certain flexibility and strength.

[0060] The results of the effects of different glycerol contents on the properties of edible films are as follows Figure 3 As shown in the figure, when the glycerol concentration is high, the adhesion index decreases, and WVP and transparency continue to increase. Since the added glycerol reduces the intermolecular force, the film is given flexibility, the elongation increases, and the tensile strength decreases. When the glycerol concentration is 2%, the adhesion index is the highest, the WVP and transparency are good, and the edible film has certain mechanical properties.

[0061] Effects of different phospholipid contents on the properties of edible films Figure 4 As shown in the figure, lipids can improve the water barrier properties of polysaccharide edible films. With the increase of phospholipid concentration, the adhesion index continued to rise, WVP fluctuated, and transparency, tensile strength and elongation continued to decline. Compared with no addition, when the phospholipid concentration was 0.05%, the adhesion index increased and the WVP was the lowest, which was 0.30 g·mm / m 2 ·h·Kpa, at this time, the transparency, tensile strength and elongation are the highest, and the performance of the film is better.

[0062] In summary, the optimal dosage (mass fraction) of the coating solution is 1.00% sodium carboxymethyl cellulose, 0.75% gum arabic, 2% glycerol, and 0.05% phospholipids.

[0063] Example 2: Detection of the effect of different antioxidants

[0064] Based on the optimal coating solution formulation of Example 1, the effects of different antioxidants were tested.

[0065] 0.15% by mass of TBHQ, walnut seed coat extract or rosemary extract was added to the coating solution, and after mixing, DPPH scavenging rate, ABTS scavenging rate and ferric ion reducing ability (FRAP) antioxidant tests were performed.

[0066] The results are as follows Figure 5 As shown, the results showed that the DPPH scavenging effect of the coating solution with TBHQ was slightly better than that of the coating solution with seed coat extract, and significantly better than that of the coating solution with rosemary extract, and the half inhibition concentrations (IC50) were 5.17, 7.39, and 25.43 μg / mL, respectively; the ability of the coating solution with TBHQ to scavenge ABTS free radicals was better than that of the coating solution with seed coat extract, and significantly better than that of the coating solution with rosemary extract, and the IC50 were 7.77, 14.45, and 37.93 μg / mL, respectively; the iron ion reducing ability of the coating solution with TBHQ was significantly the strongest, and the reducing power of the coating solution with seed coat extract was greater than that of the coating solution with rosemary extract, and the FRAP values ​​(1mmol / L) were 82.91, 275.21, and 396.87 μg / mL, respectively.

[0067] The above results show that the DPPH, ABTS and FRAP test results of the three substances are consistent, and the free radical scavenging ability and reducing power are: TBHQ>seed coat extract>rosemary extract.

[0068] On the basis of the above results, a certain amount of citric acid (CA) and vitamin C (VC) were added to the walnut seed coat extract and TBHQ coating solution, and the DPPH and ABTS free radical scavenging ability tests were carried out. The Bliss interaction evaluation model was used to calculate the synergy (S), S = 1 for additive effect, S>1 for synergistic effect, and S<1 for antagonistic effect.

[0069] DPPH removal results are as follows Figure 6 As shown in the figure, the results show that with the increase of CA concentration, the theoretical and actual values ​​(25%-45%) of the DPPH clearance rate of the two substances increased to a flat level, the synergy decreased slightly and was less than 1, and the overall effect was antagonistic. With the increase of VC concentration, the theoretical values ​​of the DPPH clearance rate of the two substances first increased and then decreased, and the actual values ​​increased to a flat level (53%-97%), the synergy increased, and the overall effect was synergistic.

[0070] ABTS removal results are as follows Figure 7As shown in the figure, the results show that with the increase of CA concentration, the theoretical values ​​of ABTS clearance rate of the two substances remain basically unchanged, the actual value (11%-44%) decreases, the synergy decreases significantly, and the overall effect changes from synergy to antagonism. With the increase of VC concentration, the theoretical and experimental values ​​(53%-100%) of ABTS clearance rate of the two substances increase to a flat level, the synergy between seed coat extract and VC remains basically unchanged, S=1, and the overall effect is additive, and the synergy between TBHQ and VC continues to decrease, and the overall effect changes from synergy to additive.

[0071] The above results show that the best effect is achieved when the addition ratio of TBHQ and VC is 1:2, that is, the optimal coating solution formula (mass fraction) is 1.00% sodium carboxymethyl cellulose, 0.75% gum arabic, 2% glycerol, 0.05% phospholipids, 0.05% TBHQ, and 0.1% VC.

[0072] In addition, the actual and theoretical values ​​of the free radical scavenging rate of the seed coat extract and CA / VC compound coating liquid were both lower than those of the coating liquid with TBHQ added, and the synergistic degree was high. Although the antioxidant activity of walnut seed coat extract was weaker than that of TBHQ, the synergist could improve its antioxidant activity to a certain extent. When the addition ratio of VC and seed coat extract was 2:3, its free radical scavenging rate was as high as more than 90%, which was basically consistent with the antioxidant activity of TBHQ.

[0073] CA and VC have a certain synergistic effect on walnut seed coat extract and TBHQ. The antioxidant effect of VC combined with VC is better than that of CA, and the amount of VC used is less than that of CA. This may be because VC has a strong reducing property, providing hydrogen atoms to the dehydrogenated polyphenols in the seed coat extract, and the acidic conditions make it more stable; VC regenerates TBHQ by reducing tert-butyl-p-benzoquinone (TQ) generated after TBHQ oxidation.

[0074] Comparative Example 1: No TBHQ added

[0075] Based on the optimal coating liquid formula of Example 2, TBHQ was not added, and a consistent total amount of Vc (0.15%) was added. The remaining steps were consistent with Example 2.

[0076] Comparative Example 2: Using other antioxidants

[0077] Based on the optimal coating solution formula of Example 2, TBHQ was replaced by BHA, and the remaining steps were consistent with Example 2. Comparative Example 3: Using other antioxidants

[0078] On the basis of the optimal coating liquid formula of Example 2, TBHQ was replaced by BHT, and the remaining steps were consistent with Example 2, and the acid value and peroxide value of the sample were tested.

[0079] Comparative Example 4: Use of other antioxidants

[0080] On the basis of the optimal coating solution formula of Example 2, TBHQ was replaced by PG, and the remaining steps were consistent with Example 2, and the acid value and peroxide value of the sample were tested.

[0081] Comparative Example 5: Use of other antioxidants

[0082] On the basis of the optimal coating solution formula of Example 2, TBHQ was replaced by tocopherol, and the remaining steps were consistent with Example 2, and the acid value and peroxide value of the sample were tested.

[0083] Comparative Example 6: Changing the formula

[0084] The formula of the coating solution was changed to (mass fraction): 1.5% sodium alginate, 0.05% Vc, 0.02% TBHQ, and the remaining steps were consistent with Example 1. The acid value and peroxide value of the sample were tested.

[0085] Take the samples prepared in Comparative Example 2 and Comparative Examples 1 to 6, and test the acid value and peroxide value. The testing steps are as follows:

[0086] The dried peeled walnut kernels were immersed in the coating liquid for 2 minutes, quickly taken out and drained, and then vacuum dried at 50°C for 9 hours to obtain the coated peeled walnut kernels, which were then vacuum packed. The samples were placed in an oven at 60°C for accelerated oxidation for 30 days, and their acid value and peroxide value were determined.

[0087] The results are shown in Table 2. The results show that the coating solution under the optimal formula of Example 2 has the best antioxidant effect, which is better than Comparative Examples 1-6.

[0088] Table 2 Acid value and peroxide value of peeled walnut kernels coated with different antioxidants after oxidation for 5 days (accelerated oxidation in a 60°C oven)

[0089]

[0090]

[0091] Example 3: Application of edible coating to extend the shelf life of nuts

[0092] The optimal coating liquid formula of Example 2 was used to detect the antioxidant effect on blanched walnut kernels, and the steps were as follows:

[0093] The dried peeled walnut kernels were immersed in the coating liquid for 2 minutes, quickly taken out and drained, and vacuum dried at 60°C for 10 hours (the parameters in the embodiment should be expressed in the form of point values). The coated peeled walnut kernels were obtained and vacuum packed. The samples were placed in an oven at 60°C for accelerated oxidation for 30 days, and their acid value and peroxide value were measured.

[0094] The acid value and peroxide value (POV) oxidation kinetic model was established. The test results of Example 2 are as follows: Figure 8 As shown, the results show that the POV kinetic model has a better fitting effect, Ln(POV) = 0.0576t-1.6465 (t is the number of days); the uncoated peeled walnut kernel has a noticeable rancid smell after 15 days of oxidation, and the POV is about 1.50mmol / kg. According to the model, it is found that the peroxide value is still less than 1.50mmol / kg after 30 days of oxidation, and there is no obvious rancid smell. Since the storage days of walnuts at room temperature are about 12 times that of accelerated oxidation at 60℃, the shelf life of the coated peeled walnut kernels at room temperature and vacuum under the optimal formula is predicted to be 12 months.

[0095] Example 4: Film application on other nuts

[0096] The optimal edible film formula was selected to soak and coat macadamia nuts and hazelnuts, and the acid value and peroxide value of the films were measured after 30 days of oxidation. The results are shown in Fig. 9 The results showed that the physical and chemical indicators of the coated nuts were significantly lower than those of the uncoated nuts, and were all lower than the limits of the acid value and peroxide value of nuts in the national standard. Among them, the coating formula was more effective in delaying the oxidative rancidity of macadamia oil.

[0097] In addition, the test found that the coated macadamia nuts and hazelnuts did not have a rancid smell after 30 days of oxidation.

[0098] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for preparing an edible coating, characterized in that: The steps include: Mixing sodium carboxymethyl cellulose, gum arabic, glycerin, phospholipids, tert-butylhydroquinone and vitamin C to prepare a coating liquid, casting into a film, and preparing an edible coating film; Alternatively, the food is immersed in the coating liquid to prepare an edible coating on the surface of the food.

2. The preparation method according to claim 1, characterized in that: The coating liquid contains, by mass fraction, 0.05-3.00% sodium carboxymethyl cellulose, 0.01-1.00% gum arabic, 1.00-3.00% glycerol, 0.01-1.00% phospholipid, 0.03-0.08% tert-butylhydroquinone and 0.10-0.20% vitamin C.

3. The preparation method according to claim 1, characterized in that: The mixing is carried out by stirring at 1500-3000 rpm until dissolved, and ultrasonic degassing is performed.

4. The preparation method according to claim 1, characterized in that: The casting film is to introduce the coating liquid into a container, and vacuum dry it at 50-90°C for 8-10 hours or dry it at normal pressure for 10-20 hours.

5. The preparation method according to claim 1, characterized in that: Soaking the food in the coating liquid means soaking the food in the coating liquid for 1-10 minutes.

6. An edible coating prepared by the method according to any one of claims 1 to 5.

7. A packaging material comprising the edible coating according to claim 6.

8. The packaging material according to claim 7, characterized in that: Packaging materials are used to package fruits, vegetables and fresh food, which can extend the shelf life of fruits, vegetables and fresh food.

9. Use of the edible coating according to claim 6 in the fields of food, medicine, agricultural products or textiles.

10. A method for extending the shelf life of nuts, characterized in that: Wrapping nuts with the film according to any one of claims 1 to 5; or soaking nuts in the coating liquid for 1 to 10 minutes; The coating liquid is prepared by mixing sodium carboxymethyl cellulose, gum arabic, glycerol, phospholipids, tert-butylhydroquinone and vitamin C to prepare the coating liquid; Optionally, the coating liquid contains, by mass fraction, 0.05-3.00% sodium carboxymethyl cellulose, 0.01-1.00% gum arabic, 1.00-3.00% glycerol, 0.01-1.00% phospholipids, 0.03-0.08% tert-butylhydroquinone and 0.10-0.20% vitamin C.

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