阅读说明：本技术 一种干果防潮防氧化可食涂膜及其制备方法和应用 (Moisture-proof and oxidation-proof edible coating film for dried fruits and preparation method and application thereof ) 是由 尹秀莲 陈梅琳 游庆红 罗楚平 张金峰 赵增东 李彦良 邓永智 周孟婷 于 2020-12-15 设计创作，主要内容包括：本发明公开了一种干果防潮防氧化可食涂膜及其制备方法和应用,该干果防潮防氧化可食涂膜主要由山楂提取溶液中加入玫瑰花提取物和板栗粗抗氧化肽制成,所述山楂提取溶液中加入玫瑰花提取物终浓度为1.0-1.5％g/mL,板栗粗抗氧化肽终浓度为1.0-1.5％g/mL,所述山楂提取溶液为果胶含量在15-20mg/mL的山楂提取溶液。本发明是一种干果防潮防氧化的天然可食保鲜膜,该保鲜膜所用成分均来自天然可食材料提取物,可以对干果进行有效地防潮防氧化,本发明的制备方法简单方便,工艺条件易控制,成本低,易实现规模工业化生产,操作容易。(The invention discloses a moisture-proof and oxidation-proof edible coating of dried fruits and a preparation method and application thereof, wherein the moisture-proof and oxidation-proof edible coating of the dried fruits is mainly prepared by adding rose extract and crude Chinese chestnut antioxidant peptide into a hawthorn extract solution, the final concentration of the rose extract added into the hawthorn extract solution is 1.0-1.5% g/mL, the final concentration of the crude Chinese chestnut antioxidant peptide is 1.0-1.5% g/mL, and the hawthorn extract solution is a hawthorn extract solution with the pectin content of 15-20 mg/mL. The invention is a moisture-proof and oxidation-proof natural edible preservative film for dried fruits, the components of the preservative film are all from natural edible material extracts, and the preservative film can effectively prevent moisture and oxidation for the dried fruits.)

1. A dried fruit moisture-proof anti-oxidation edible coating film is characterized by being mainly prepared by adding rose extract and Chinese chestnut crude antioxidant peptide into a hawthorn extract solution, wherein the rose extract is added into the hawthorn extract solution to achieve a final concentration of 1.0-1.5% g/mL, the Chinese chestnut crude antioxidant peptide is added into the hawthorn extract solution to achieve a final concentration of 1.0-1.5% g/mL, and the hawthorn extract solution is a hawthorn extract solution with a pectin content of 15-20 mg/mL.

2. A method for preparing the moisture-proof and oxidation-proof edible coating film of the dried fruit as claimed in claim 1, which is characterized by comprising the following steps:

(1) pulverizing dried fructus crataegi, sieving to obtain fructus crataegi powder, adding distilled water into fructus crataegi powder, adjusting pH, heating for extraction, filtering, collecting filtrate, and vacuum concentrating until pectin content is 15-20mg/mL to obtain fructus crataegi extract solution;

(2) pulverizing dried flos Rosae Rugosae, reflux-extracting with ethanol water solution as solvent, filtering, collecting filtrate, concentrating under reduced pressure, and vacuum drying to obtain flos Rosae Rugosae extract;

(3) pulverizing peeled semen Castaneae, sieving, and defatting with petroleum ether to obtain defatted semen Castaneae powder; mixing defatted chestnut powder with distilled water, adjusting pH, stirring for extraction, filtering to obtain filtrate, adjusting pH for precipitation, centrifuging to remove supernatant, and oven drying the precipitate to obtain chestnut protein powder; weighing protein powder to prepare a protein aqueous solution, adjusting pH, adding alkaline protease, performing enzymolysis in water bath, centrifuging after the enzymolysis is finished, collecting supernatant, concentrating in vacuum, and freeze-drying to obtain crude antioxidant peptides of Chinese chestnut;

(4) adding rose extract and the Chinese chestnut crude antioxidant peptide into the hawthorn extract solution, and uniformly stirring to obtain the moisture-proof and oxidation-proof edible coating solution.

3. The preparation method of claim 2, wherein the dried hawthorn is pulverized in step (1), and sieved with a 50-60 mesh sieve to obtain hawthorn powder, the hawthorn powder is taken, distilled water is added according to the material-to-liquid ratio of 1:25-30g/mL, the pH value is adjusted by 1-2mol/L hydrochloric acid to be 2, reflux extraction is carried out at 90-100 ℃ for 1.5-2h, filtration is carried out, filtrate is collected, filter residue is taken for repeated extraction, extraction filtrate is combined, and vacuum concentration is carried out until the pectin content is 15-20mg/mL, so as to obtain the hawthorn extraction solution.

4. The preparation method of claim 2, wherein the dried rose buds in the step (2) are ground and sieved by a 40-50-mesh sieve, 75-80% ethanol water solution by volume fraction is used as a solvent, the mixture is subjected to reflux extraction at 80-90 ℃ for 2-3h according to the material-liquid ratio of 1:15-20g/mL, the filtration is carried out, filter residues are repeatedly extracted, the filtrates are combined, the reduced pressure concentration is carried out, and the dried rose buds are dried in a vacuum oven at 50-60 ℃ to obtain the rose extract.

5. The preparation method according to claim 2, characterized in that the peeled chestnut kernels in the step (3) are taken and crushed, sieved by a 50-60 mesh sieve, degreased by petroleum ether for 5-6h according to the material-liquid ratio of 1:20-30g/mL to obtain degreased chestnut powder, the degreased chestnut powder is taken and mixed with distilled water according to the ratio of 1:10-15g/mL, the pH value is adjusted to 9.0 by 1-2mol/L sodium hydroxide, the mixture is stirred and extracted for 80-90min at 50-60 ℃, the filtrate is taken and is adjusted to 4.0 by 1-2mol/L HCl, the precipitation is carried out for 2-3h, the centrifugation is carried out at 5000-6000rpm for 3-5min, the supernatant is discarded, and the precipitate is dried in an oven at 50-60 ℃ to obtain the chestnut protein powder.

6. The preparation method according to claim 2, characterized in that the protein powder is weighed in the step (3) to prepare a protein aqueous solution, the pH value is adjusted to 9.0 by 1-2mol/L sodium hydroxide, alkaline protease is added to make the content of the alkaline protease 5000-6000U/mL, the obtained product is placed in a water bath at 40-50 ℃ to be continuously stirred and enzymolyzed for 3-5 hours, the pH value of the solution is adjusted to be kept unchanged by 0.2-0.5mol/L sodium hydroxide in the stirring process, after the enzymolysis is finished, the obtained product is placed in a water bath at 90-100 ℃ to be inactivated for 5-10 minutes, supernatant fluid is centrifugally collected, and the obtained product is subjected to vacuum concentration and freeze drying to obtain the crude antioxidant peptide.

7. The use of the moisture-proof and oxidation-proof edible coating film of dried fruits of claim 1 in moisture-proof and oxidation-proof of dried fruits.

8. Use according to claim 7, wherein the dried fruit preferably comprises hazelnuts, cashews, walnuts, pine nuts, pistachios, pecans, almonds or macadamia nuts.

9. The application of claim 7, wherein the application process is: soaking the dried fruits in the coating solution for 1-3min, taking out, draining, oven drying at 50-60 deg.C, packaging, and storing.

Technical Field

The invention relates to the field of food processing, in particular to a moisture-proof and oxidation-proof edible coating for dried fruits and a preparation method and application thereof.

Background

Dry fruit, i.e. fruit whose pericarp is ripe and is in a dry state. Most of them are rich in protein, vitamin, lipid, etc., and are popular among people. There are many dry fruits commonly seen in our lives, such as chestnuts, castanea henryi, pili nuts, hazelnuts, cashews, walnuts, melon seeds, pinenuts, almonds, ginkgo nuts, pistachios, pecans, desert fruits, torreya seeds, pumpkin seeds, peanuts, almonds, macadamia nuts, and the like. However, the dry fruits have low water content and high oil content, and are easy to be affected with damp and oxidized in the transportation and storage process, so that the taste of the dry fruits is influenced, the quality of the dry fruits is reduced, and the commodity value is lost. A large number of dry fruits are not sold yet every year, and are softened by moisture and can not be eaten due to oxidation of grease, so that serious economic loss and resource waste are caused, and therefore, delaying oxidation of lipid and preventing moisture absorption are particularly important for storage of dry fruit foods.

The edible film can prevent gases such as water vapor, oxygen, carbon dioxide and the like, thereby playing a certain protection role on packaged food, ensuring the quality of the food and prolonging the shelf life of the food. The natural antioxidant is added into the edible film, so that the oxidative deterioration of food caused by the oxidation of air can be prevented, and the edible film has a protective effect on oil, fat-soluble components and other natural components. In addition, various adverse changes such as discoloration, generation of unpleasant odor, etc., due to oxidation of food can be delayed. The research on the current edible film used for preventing moisture and oxidation of the dried fruits is less, and the patent of a modified starch for dried fruit coating and a preparation method and application thereof (application number 201710514472.2) discloses a modified starch special for dried fruit coating and a use method thereof.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the problems in the prior art, the invention provides a moisture-proof and oxidation-proof edible film for dried fruits, which is a natural edible preservative film, and all the components of the preservative film are derived from extracts of natural edible materials, so that the moisture-proof and oxidation-proof effects can be effectively realized on the dried fruits.

The technical scheme is as follows: in order to achieve the purpose, the moisture-proof and oxidation-proof edible coating film is characterized by being mainly prepared by adding rose extract and Chinese chestnut crude antioxidant peptide into a hawthorn extract solution, wherein the rose extract is added into the hawthorn extract solution to achieve the final concentration of 1.0-1.5 percent (g/mL), the Chinese chestnut crude antioxidant peptide is added into the hawthorn extract solution to achieve the final concentration of 1.0-1.5 percent (g/mL), and the hawthorn extract solution is a hawthorn extract solution with the pectin content of 15-20 mg/mL.

The preparation method of the moisture-proof and oxidation-proof edible coating for the dried fruits comprises the following steps:

(1) pulverizing dried fructus crataegi, sieving to obtain fructus crataegi powder, adding distilled water into fructus crataegi powder, heating and extracting with pH adjusted, filtering, collecting filtrate, and vacuum concentrating until pectin content is 15-20mg/mL to obtain fructus crataegi extract solution;

(2) pulverizing dried flos Rosae Rugosae, reflux-extracting with ethanol water solution as solvent, filtering, collecting filtrate, concentrating under reduced pressure, and vacuum drying to obtain flos Rosae Rugosae extract;

(3) pulverizing peeled semen Castaneae, sieving, and defatting with petroleum ether to obtain defatted semen Castaneae powder; mixing defatted chestnut powder with distilled water, adjusting pH, stirring for extraction, filtering to obtain filtrate, adjusting pH for precipitation, centrifuging to remove supernatant, and oven drying the precipitate to obtain chestnut protein powder; weighing protein powder to prepare a protein aqueous solution, adjusting pH, adding alkaline protease, performing enzymolysis in water bath, centrifuging after the enzymolysis is finished, collecting supernatant, concentrating in vacuum, and freeze-drying to obtain crude antioxidant peptides of Chinese chestnut;

(4) adding rose extract and the Chinese chestnut crude antioxidant peptide into the hawthorn extract solution, and uniformly stirring to obtain the moisture-proof and oxidation-proof edible coating solution.

Taking dried hawthorn fruits, crushing, sieving with a 50-60-mesh sieve to obtain hawthorn powder, taking the hawthorn powder, adding distilled water according to the ratio of material to liquid of 1:25-30g/mL, adjusting the pH value to 2 by 1-2mol/L hydrochloric acid, extracting at 90-100 ℃ for 1.5-2h, filtering, collecting filtrate, taking filter residues for repeated extraction, combining the extracted filtrates, and vacuum concentrating until the pectin content is 15-20mg/mL to obtain the hawthorn extract solution.

Wherein, the dried rose buds in the step (2) are taken, crushed and sieved by a 40-50-mesh sieve, 75-80% (mL/mL) ethanol water solution with volume fraction is taken as a solvent, the mixture is extracted under reflux for 2-3h at 80-90 ℃ according to the material-liquid ratio of 1:15-20g/mL, the filtration is carried out, the filter residues are taken for repeated extraction, the filtrates are combined, the reduced pressure concentration is carried out, and the dried rose extracts are obtained after drying in a vacuum oven at 50-60 ℃.

Crushing peeled Chinese chestnut kernels, sieving the crushed Chinese chestnut kernels with a 50-60-mesh sieve, degreasing the crushed Chinese chestnut kernels with petroleum ether for 5-6h according to the material-liquid ratio of 1:20-30g/mL to obtain degreased Chinese chestnut powder, mixing the degreased Chinese chestnut powder with distilled water according to the ratio of 1:10-15g/mL, adjusting the pH value to 9.0 with 1-2mol/L sodium hydroxide, stirring and extracting the mixture at 50-60 ℃ for 80-90min, filtering the mixture, adjusting the pH value to 4.0 with 1-2mol/L HCl, precipitating the mixture for 2-3h, centrifuging the mixture at 6000rpm of 5000 and 5000 for 3-5min, discarding the supernatant, and drying the precipitate in an oven at 50-60 ℃ to obtain the Chinese chestnut protein powder.

Weighing the protein powder in the step (3) to prepare a protein aqueous solution, adjusting the pH value to 9.0 by 1-2mol/L sodium hydroxide, adding alkaline protease to make the content of the alkaline protease to be 5000-6000U/mL, putting the solution into a water bath at the temperature of 40-50 ℃ to be continuously stirred for enzymolysis for 3-5 hours, adjusting the pH value of the solution to be kept unchanged by using 0.2-0.5mol/L sodium hydroxide in the stirring process, after the enzymolysis is finished, putting the solution into a water bath at the temperature of 90-100 ℃ to inactivate the enzyme for 10 minutes, centrifugally collecting supernate, concentrating in vacuum, and freeze-drying to obtain the crude antioxidant peptide of the Chinese chestnut.

Preferably, the dried hawthorn fruits are taken and crushed in the step (1), the dried hawthorn fruits are sieved by a 50-mesh sieve to obtain hawthorn powder, the hawthorn powder is taken, distilled water is added according to the material-liquid ratio of 1:30g/mL, the pH value is adjusted to 2 by 1mol/L hydrochloric acid, extraction is carried out at 90 ℃ for 2 hours, filtration is carried out, filtrate is collected, filter residue is taken for repeated extraction, the extraction filtrate is combined, and vacuum concentration is carried out until the pectin content is 15-20mg/mL, so that the hawthorn extraction solution is obtained.

Preferably, the dried rose buds in the step (2) are ground and sieved by a 40-mesh sieve, 75% mL/mL ethanol water solution is used as a solvent, the mixture is extracted under reflux at 90 ℃ for 2 hours according to the material-liquid ratio of 1:15g/mL, the filtration is carried out, filter residues are extracted repeatedly, the filtrates are combined, the reduced pressure concentration is carried out, and the drying is carried out in a vacuum oven at 50 ℃ to obtain the rose extract.

Preferably, the peeled chestnut kernels are taken and crushed in the step (3), screened by a 50-mesh sieve, degreased by petroleum ether for 6h according to the feed-liquid ratio of 1:20(g/mL) to obtain degreased chestnut powder, the degreased chestnut powder is mixed with distilled water according to the ratio of 1:10g/mL, the pH value is adjusted to 9.0 by 1mol/L sodium hydroxide, the mixture is stirred and extracted for 90min at 50 ℃, filtered, the filtrate is taken, the pH value is adjusted to 4.0 by 1mol/L HCl, the precipitate is precipitated for 2h at 5000rpm for 5min, the supernatant is discarded, and the precipitate is dried in an oven at 50 ℃ to obtain the chestnut protein powder.

Preferably, the protein powder is weighed in the step (3) to prepare a protein aqueous solution, the pH value is adjusted to 9.0 by 1mol/L sodium hydroxide, alkaline protease is added to make the content of the alkaline protease 5000U/mL, the mixture is placed into a water bath at 50 ℃ to be continuously stirred and enzymolyzed for 3 hours, the pH value of the solution is adjusted to be kept unchanged by 0.2mol/L sodium hydroxide in the stirring process, and after the enzymolysis is finished, the mixture is placed into a water bath at 90 ℃ to be inactivated for 10 minutes. Centrifuging at 5000rpm for 5min, collecting supernatant, vacuum concentrating, and freeze drying to obtain semen Castaneae crude antioxidant peptide.

The moisture-proof and oxidation-proof edible coating film for the dried fruits is applied to moisture-proof and oxidation-proof of the dried fruits.

Wherein the dried fruit comprises hazelnut, cashew nut, walnut, pine nut, pistachio nut, pecan, almond or macadamia nut.

Wherein the application comprises the following steps: and (3) completely soaking the dried fruits in the coating solution for 1-3min, taking out, draining the solution, drying in a 50 ℃ oven, and conventionally packaging and storing.

The moisture-proof antioxidant coating film is prepared by mixing a hawthorn extract solution, a rose extract and Chinese chestnut crude antioxidant peptide, has a synergistic effect, and has a better preservation effect than that of a single component.

Has the advantages that: compared with the prior art, the invention has the following remarkable advantages:

1. the main component of the hawthorn extract solution in the moisture-proof and oxidation-proof edible coating of the dried fruit is pectin and contains a certain amount of fruit wax component, the hawthorn extract solution is directly used for film forming, the pectin purification steps are reduced, the pectin and the fruit wax can form a layer of protective film on the surface of the dried fruit, and the fruit wax has a certain waterproof effect and can better prevent moisture absorption.

2. The rose extract mainly contains rose polyphenol and flavone, the hawthorn extract contains a certain amount of hawthorn polyphenol and flavone, the Chinese chestnut crude antioxidant peptide mainly contains antioxidant peptide, the compounds not only have high antioxidant and antibacterial activities in vitro and are ingested by human bodies, but also have activities of removing free radicals, reducing blood fat and the like, and the three compounds have very obvious synergistic action in the aspect of antioxidation.

3. The moisture-proof and oxidation-proof edible coating for the dried fruits, which is prepared by the invention, does not change the original production process of dried fruit products and is convenient to operate; both the hawthorn extract solution peel and the rose extract have pleasant fresh scent, and even if left on the dried fruit, do not cause unpleasant taste to the consumer.

4. The preparation method is simple and convenient, the process conditions are easy to control, the cost is low, the large-scale industrial production is easy to realize, and the operation is easy.

Drawings

FIG. 1 is a schematic representation of water activity as a function of time;

FIG. 2 is a graph showing the change of peroxide number with time.

Detailed description of the invention

The invention is further illustrated by the following figures and examples.

Materials, reagents and the like used in the following examples are commercially available unless otherwise specified. The experimental procedures, in which specific conditions are not indicated in the examples, are generally carried out under conventional conditions or conditions recommended by the manufacturer.

Example 1

(1) Pulverizing dried fructus crataegi, and sieving with 50 mesh sieve to obtain fructus crataegi powder. Adding distilled water into hawthorn powder according to the ratio of material to liquid of 1:30(g/mL), adjusting the pH value to 2 by 1mol/L hydrochloric acid, carrying out reflux extraction at 90 ℃ for 2h, filtering, collecting filtrate, and repeatedly extracting filter residue once. Mixing the two extractive filtrates, and vacuum concentrating to pectin content of 20mg/mL to obtain fructus crataegi extractive solution.

(2) Pulverizing dried flos Rosae Rugosae, sieving with 40 mesh sieve, reflux extracting with 75% (mL/mL) ethanol water solution as solvent at 90 deg.C for 2 hr at a material-to-liquid ratio of 1:15(g/mL), filtering, repeating the extraction for 2 times, mixing filtrates, concentrating under reduced pressure, and oven drying at 50 deg.C in a vacuum oven to obtain flos Rosae Rugosae extract.

(3) Crushing peeled Chinese chestnut kernels, sieving with a 50-mesh sieve, and degreasing with petroleum ether for 6h according to the material-liquid ratio of 1:20(g/mL) to obtain degreased Chinese chestnut powder. Mixing defatted chestnut powder with distilled water at a ratio of 1:10(g/mL), adjusting pH to 9.0 with 1mol/L sodium hydroxide solution, extracting at 50 deg.C under stirring for 90min, filtering, collecting filtrate, adjusting pH to 4.0 with 1mol/L HCl, precipitating for 2h, centrifuging at 5000rpm for 5min, discarding supernatant, and oven drying at 50 deg.C to obtain chestnut protein powder. Weighing protein powder, preparing into protein water solution, adjusting pH to 9.0 with 1mol/L sodium hydroxide solution, adding alkaline protease to make its content be 5000U/mL, placing into 50 deg.C water bath, continuously stirring for enzymolysis for 3 hr, adjusting pH with 0.2mol/L sodium hydroxide solution to maintain unchanged, after enzymolysis, placing into 90 deg.C water bath to inactivate enzyme for 10min, centrifuging at 5000rpm for 5min, collecting supernatant, vacuum concentrating, and freeze drying to obtain crude antioxidant peptide of semen Castaneae.

(4) Adding rose extract with a final concentration of 1.0% (g/mL) and Chinese chestnut crude antioxidant peptide with a final concentration of 1.0% (g/mL) into the hawthorn extract solution, and stirring and uniformly mixing to obtain the moisture-proof and oxidation-proof edible coating solution.

(5) And (3) completely soaking the dried fruits in the coating solution for 1min, taking out, draining the solution, drying in a 50 ℃ oven, and conventionally packaging and storing.

Example 2

(1) Pulverizing dried fructus crataegi, and sieving with 55 mesh sieve to obtain fructus crataegi powder. Adding distilled water into hawthorn powder according to the ratio of material to liquid of 1:30(g/mL), adjusting the pH value to 2 by 1mol/L hydrochloric acid, carrying out reflux extraction at 90 ℃ for 2h, filtering, collecting filtrate, and repeatedly extracting filter residue once. Mixing the two extractive filtrates, and vacuum concentrating until pectin content is 15mg/mL to obtain fructus crataegi extractive solution.

(2) Pulverizing dried flos Rosae Rugosae, sieving with 45 mesh sieve, reflux extracting with 80% (mL/mL) ethanol water solution as solvent at 80 deg.C for 2 hr at a material-to-liquid ratio of 1:15(g/mL), filtering, repeating the extraction for 2 times, mixing filtrates, concentrating under reduced pressure, and oven drying in a vacuum oven at 50 deg.C to obtain flos Rosae Rugosae extract.

(3) And (3) crushing the peeled Chinese chestnut kernels, sieving the crushed Chinese chestnut kernels with a 50-mesh sieve, and degreasing the crushed Chinese chestnut kernels with petroleum ether for 6 hours to obtain degreased Chinese chestnut powder. Mixing defatted chestnut powder with distilled water at a ratio of 1:10(g/mL), adjusting pH to 9.0 with 1mol/L sodium hydroxide solution, extracting at 50 deg.C under stirring for 90min, filtering, collecting filtrate, adjusting pH to 4.0 with 1mol/L HCl, precipitating for 2h, centrifuging at 5000rpm for 5min, discarding supernatant, and oven drying at 50 deg.C to obtain chestnut protein powder. Weighing protein powder, preparing into protein water solution, adjusting pH to 9.0 with 1mol/L sodium hydroxide, adding alkaline protease to reach 5500U/mL content, placing into 50 deg.C water bath, continuously stirring for enzymolysis for 3 hr, adjusting pH with 0.2mol/L sodium hydroxide solution, maintaining, and inactivating enzyme in 90 deg.C water bath for 10min after enzymolysis. Centrifuging at 5000rpm for 5min, collecting supernatant, vacuum concentrating, and freeze drying to obtain semen Castaneae crude antioxidant peptide.

(4) Adding rose extract with a final concentration of 1.5% (g/mL) and Chinese chestnut crude antioxidant peptide with a final concentration of 1.5% (g/mL) into the hawthorn extract solution, and uniformly stirring to obtain the moisture-proof and oxidation-proof edible coating solution.

(5) And (3) completely soaking the dried fruits in the coating solution for 1min, taking out, draining the solution, drying in an oven at 55 ℃, and then packaging and storing conventionally.

Example 3

(1) Pulverizing dried fructus crataegi, and sieving with 60 mesh sieve to obtain fructus crataegi powder. Adding distilled water into fructus crataegi powder at a ratio of 1:30(g/mL), adjusting pH to 2 with 1mol/L hydrochloric acid, extracting at 90 deg.C for 2 hr, filtering, collecting filtrate, and extracting residue once again. Mixing the two extractive filtrates, and vacuum concentrating to pectin content of 18mg/mL to obtain fructus crataegi extractive solution.

(2) Pulverizing dried flos Rosae Rugosae, sieving with 40 mesh sieve, extracting with 75% (mL/mL) ethanol water solution as solvent at 85 deg.C under reflux at a material-to-liquid ratio of 1:15(g/mL) for 2 hr, filtering, extracting repeatedly for 2 times, mixing filtrates, concentrating under reduced pressure, and oven drying at 50 deg.C in vacuum oven to obtain flos Rosae Rugosae extract.

(3) Crushing peeled Chinese chestnut kernels, sieving with a 55-mesh sieve, and degreasing with petroleum ether for 6h according to the material-liquid ratio of 1:20(g/mL) to obtain degreased Chinese chestnut powder. Mixing defatted chestnut powder with distilled water at a ratio of 1:10(g/mL), adjusting pH to 9.0 with 1mol/L sodium hydroxide solution, extracting at 50 deg.C under stirring for 90min, filtering, collecting filtrate, adjusting pH to 4.0 with 1mol/L HCl, precipitating for 2h, centrifuging at 5000rpm for 5min, discarding supernatant, and oven drying at 50 deg.C to obtain chestnut protein powder. Weighing protein powder, preparing into protein water solution, adjusting pH to 9.0 with 1mol/L sodium hydroxide, adding alkaline protease to make its content be 6000U/mL, placing into 50 deg.C water bath, continuously stirring for enzymolysis for 3 hr, adjusting pH with 0.2mol/L sodium hydroxide solution to maintain unchanged, and inactivating enzyme in 90 deg.C water bath for 10min after enzymolysis. Centrifuging at 5000rpm for 5min, collecting supernatant, vacuum concentrating, and freeze drying to obtain semen Castaneae crude antioxidant peptide.

(4) Adding rose extract with a final concentration of 1.2% (g/mL) and Chinese chestnut crude antioxidant peptide with a final concentration of 1.3% (g/mL) into the hawthorn extract solution, and stirring and uniformly mixing to obtain the moisture-proof and oxidation-proof edible coating solution.

(5) And (3) completely soaking the dried fruits in the coating solution for 1min, taking out, draining the solution, drying in a 60 ℃ oven, and conventionally packaging and storing.

Example 4

(1) Pulverizing dried fructus crataegi, and sieving with 60 mesh sieve to obtain fructus crataegi powder. Adding distilled water into fructus crataegi powder at a ratio of 1:25(g/mL) to obtain a mixture, adjusting pH to 2 with 2mol/L hydrochloric acid, reflux-extracting at 100 deg.C for 1.5h, filtering, collecting filtrate, and extracting residue once again. Mixing the two extractive filtrates, and vacuum concentrating to pectin content of 20mg/mL to obtain fructus crataegi extractive solution.

(2) Pulverizing dried flos Rosae Rugosae, sieving with 50 mesh sieve, reflux extracting with 78% (mL/mL) ethanol water solution as solvent at 90 deg.C for 2 hr at a material-to-liquid ratio of 1:20(g/mL), filtering, repeating the extraction for 2 times, mixing filtrates, concentrating under reduced pressure, and oven drying at 60 deg.C in vacuum oven to obtain flos Rosae Rugosae extract.

(3) Crushing peeled Chinese chestnut kernels, sieving with a 60-mesh sieve, and defatting with petroleum ether for 5h according to the material-liquid ratio of 1:30(g/mL) to obtain defatted Chinese chestnut powder. Mixing defatted chestnut powder with distilled water at a ratio of 1:15(g/mL), adjusting pH to 9.0 with 2mol/L sodium hydroxide solution, extracting at 60 deg.C under stirring for 80min, filtering, collecting filtrate, adjusting pH to 4.0 with 2mol/L HCl, precipitating for 3h, centrifuging at 6000rpm for 3min, discarding supernatant, and oven drying at 60 deg.C to obtain chestnut protein powder. Weighing protein powder, preparing into protein water solution, adjusting pH to 9.0 with 2mol/L sodium hydroxide solution, adding alkaline protease to make its content be 6000U/mL, placing into 40 deg.C water bath, continuously stirring for enzymolysis for 5 hr, adjusting pH with 0.5mol/L sodium hydroxide solution to maintain unchanged, after enzymolysis, placing into 100 deg.C water bath to inactivate enzyme for 5min, centrifuging at 5000rpm for 5min, collecting supernatant, vacuum concentrating, and freeze drying to obtain crude antioxidant peptide of semen Castaneae.

(4) Adding rose extract with a final concentration of 1.0% (g/mL) and Chinese chestnut crude antioxidant peptide with a final concentration of 1.0% (g/mL) into the hawthorn extract solution, and stirring and uniformly mixing to obtain the moisture-proof and oxidation-proof edible coating solution.

(5) And (3) completely soaking the dried fruits in the coating solution for 3min, taking out, draining the solution, drying in a 50 ℃ oven, and conventionally packaging and storing.

Test example 1

The moisture-proof and oxidation-resistant coating films prepared in examples 1 to 3 and comparative examples 1 to 5 of the present invention were used to treat walnut kernels, and the change of the moisture-proof and oxidation-resistant effects of the walnut kernels in a constant temperature and humidity state (temperature 39 ℃ and relative humidity 90% to 93%) with time was examined, and the results are shown in fig. 1 and fig. 2.

Wherein comparative example 1, conventional preserved walnut kernels were not treated with the moisture-proof and antioxidant coating film prepared according to the present invention;

comparative example 2 walnut kernels were treated with a modified starch for dry fruit coating and its preparation method and use (application No. 201710514472.2) in the prior art under the same conditions;

comparative example 3 is the pure hawthorn extract solution prepared in example 1 of the present invention, and the walnut kernels were processed according to step (5) in example 1;

comparative example 4 is the pure hawthorn extract solution prepared in example 1 of the present invention, and only rose extract 1.0% (g/mL) prepared in example 1 was added and walnut kernels were processed according to step (5) of example 1.

Comparative example 5 is a pure hawthorn extract solution prepared in example 1 of the present invention, to which only 1.0% (g/mL) of the chestnut crude antioxidant peptide of example 1 was added, and walnut kernels were processed according to step (5) of example 1.

From the results of fig. 1, it can be seen that the moisture-proof and antioxidant edible coating films prepared in examples 1-3 of the present invention and the walnut kernels treated in comparative examples 3-5 have a slow increase in water activity at a temperature of 39 ℃ and a relative humidity of 90% -93%, the water activity of comparative example 1 increases rapidly, and the water activity of comparative example 2 increases slightly more than those of examples 1-3 and comparative examples 3-5 and less than that of comparative example 1, indicating that the starch coating film can be moisture-proof to some extent, but has a poor effect as compared with the coating film of the present invention.

As can be seen from the results in FIG. 2, after the walnut kernels are treated by the moisture-proof, oxidation-resistant and edible coating films prepared in the examples 1 to 3 of the invention, under the conditions that the temperature is 39 ℃ and the relative humidity is 90-93%, the peroxide value is slowly increased, the peroxide value is more than 0.08g/100g at 42 days (the peroxide value is less than or equal to 0.08g/100g according to the national standard of GB 19300-2014 food safety) and the peroxide value is more than 0.08g/100g at 28 days in the comparative examples 3 to 5, which shows that the effect of adding the rose extract or the chestnut crude oxidation-resistant peptide in the hawthorn extract solution is worse than that of adding the rose extract and the chestnut crude oxidation-resistant peptide simultaneously, and the moisture-proof, oxidation-resistant and edible coating films of the dried fruits of the invention are similar to the comparative examples 3 to 5 after the walnut kernels are physically coated by using any one or two of the three, the effect is obviously not as good as that of the invention; in addition, as can be seen from the curve amplification in fig. 2 of the present invention, the antioxidant effect of the hawthorn extract solution added with rose extract alone or the chestnut crude antioxidant peptide alone is only slightly improved compared with that of the single hawthorn extract solution, but after the three raw material substances are added simultaneously, the antioxidant effect is significantly improved, which indicates that the three raw materials are required to be used in combination to achieve a synergistic effect, and a good effect is achieved. The peroxide value increasing speed of comparative example 1 and comparative example 2 is higher than that of examples 1-3, which shows that the moisture-proof and oxidation-resistant effect of the invention on walnut kernels is better.