阅读说明：本技术 一种果蔬用蛋白防腐涂层及其制备方法 (Protein anticorrosive coating for fruits and vegetables and preparation method thereof ) 是由 卜云飞 王耀彬 顾娅馨 张芸榕 费嘉雯 于 2020-12-11 设计创作，主要内容包括：本发明公开了一种果蔬用蛋白防腐涂层及其制备方法,该防腐涂层包括质量比为20～25：6～8：1～2：6～8的蛋清、甘油、蛋黄、抗氧化剂和纤维素纳米晶；该防腐涂层的制备方法包括以下步骤：(1)制备纤维素纳米晶；(2)取鸡蛋清分散到水中,加入甘油搅拌,然后将混合液pH值调整到10～12,继续搅拌至混合液均匀；(3)将抗氧化剂分散在水中后加入步骤(2)中的混合液中继续搅拌；(4)将纤维素纳米晶分散在水中后加入步骤(3)中的混合液中搅拌至均匀,然后冷却至室温。该涂层能够抑制微生物生长,同时降低微环境中的O-2和CO-2,能够保持水果的新鲜度良好的机械性能、保鲜性和抗菌性,形成的薄膜具有良好的机械性能,并且对人体无毒无害,易清洗,制备简单。(The invention discloses a protein anticorrosive coating for fruits and vegetables and a preparation method thereof, wherein the anticorrosive coating comprises the following components in mass ratio of 20-25: 6-8: 1-2: 6-8 of egg white, glycerol, egg yolk, an antioxidant and cellulose nanocrystals; the preparation method of the anticorrosive coating comprises the following steps: (1) preparing cellulose nanocrystals; (2) dispersing egg white into water, adding glycerol, stirring, adjusting the pH value of the mixed solution to 10-12, and continuously stirring until the mixed solution is uniform; (3) dispersing an antioxidant in water, adding the antioxidant into the mixed solution obtained in the step (2), and continuously stirring; (4) and (4) dispersing the cellulose nanocrystals in water, adding the dispersed cellulose nanocrystals into the mixed solution obtained in the step (3), stirring the mixture until the mixture is uniform, and then cooling the mixture to room temperature. The coating can inhibit the growth of microorganisms and simultaneously reduce O in the microenvironment 2 And CO 2 Machine capable of keeping good freshness of fruitsThe formed film has good mechanical property, is nontoxic and harmless to human bodies, is easy to clean and is simple to prepare.)

1. The protein anticorrosive coating for fruits and vegetables is characterized by comprising the following components in percentage by mass of 10-30: 6-8: 2-3: 1-2: 6-8 of egg white, glycerol, an edible hydrophobing agent, an antioxidant and cellulose nanocrystals.

2. The egg white preservative coating for fruits and vegetables according to claim 1, wherein the edible hydrophobic agent is egg yolk.

3. The protein anticorrosive coating for fruits and vegetables according to claim 1, wherein the antioxidant is curcumin, tea polyphenol or allicin with purity of not less than 99.5%.

4. The preparation method of the protein anticorrosive coating for fruits and vegetables, which is characterized by comprising the following steps of:

(1) preparing cellulose nanocrystals;

(2) dispersing egg white into water, adding glycerol, stirring, adjusting the pH value of the mixed solution to 10-12, and continuously stirring until the mixed solution is uniform;

(3) dispersing an antioxidant in water, adding the antioxidant into the mixed solution obtained in the step (2), and continuously stirring;

(4) and (4) dispersing the cellulose nanocrystals in water, adding the dispersed cellulose nanocrystals into the mixed solution obtained in the step (3), stirring the mixture until the mixture is uniform, and then cooling the mixture to room temperature.

5. The preparation method of the protein anticorrosive coating for fruits and vegetables according to claim 4, wherein the step (1) comprises the following steps:

(11) placing tea stalk powder in a Soxhlet extractor, adding a benzene-alcohol solution for extraction for 6-8 h, and naturally drying for later use;

(12) placing the extracted tea stalk powder in a shaking water bath, adding NaClO₂Mixing the powder with glacial acetic acid until the sample turns white, washing to neutrality, and freeze-drying;

(13) putting the tea stalk powder treated in the step (12) into a KOH solution for water bath treatment, washing to be neutral, and freeze-drying for later use;

(14) and (3) placing the tea stem powder treated in the step (13) in a sulfuric acid solution, uniformly stirring, adding distilled water to terminate the reaction, dialyzing to be neutral to obtain a CNC colloid, centrifugally separating and purifying a sample, and freeze-drying to obtain the cellulose nanocrystal.

6. The preparation method of the protein anticorrosive coating for fruits and vegetables according to claim 5, wherein the benzene-alcohol solution in the step (11) is a toluene/ethanol mixed solution with a volume ratio of 1-2: 1, and the extraction temperature is 90-95 ℃; the water bath temperature in the step (12) is 75-80 ℃, and the tea stem powder and NaClO are₂The usage amount of the powder and the glacial acetic acid is 4 g: 7-9 g: 1mL of NaClO₂Adding the powder and glacial acetic acid into the reaction solution for 5-6 times every 1-2 h, wherein the water bath temperature in the step (13) is 80-85 ℃, and the usage amount of the tea stem powder and the KOH solution is 4 g: 100-120 mL of KOH solution, wherein the mass fraction of the KOH solution is 8% -10%; in the step (14), the stirring temperature of the tea stalk powder in the sulfuric acid solution is 45-50 ℃, and the usage amount of the tea stalk powder and the sulfuric acid solution is 2 g: 30-40 mL, and the mass percent of the sulfuric acid solution is 63-68%.

7. The preparation method of the protein anticorrosive coating for fruits and vegetables according to claim 4, wherein the volume usage amount of egg white and water in the step (2) is 1 g: 15-20 mL, using sodium hydroxide pellets when adjusting the pH, and stirring at 80-90 ℃.

8. The method for preparing the egg white anticorrosive coating for fruits and vegetables according to claim 4, wherein the uniformly dispersed egg yolk solution is added to the mixed solution of the eggs and the glycerin in the step (2).

Technical Field

The invention relates to an anticorrosive coating and a preparation method thereof, and particularly relates to a protein anticorrosive coating for fruits and vegetables and a preparation method thereof.

Background

According to statistics, one third of perishable grains produced globally cause a great deal of waste due to overlong transportation time, lower preservation technology and the like. This problem is particularly pronounced in fresh produce such as fruits and vegetables, where about 40% to 50% of the produce fruits are directly discarded annually due to spoilage problems, and the major factors affecting the quality and post-harvest life of these produce are water loss or dehydration, deterioration in texture, respiration and aging processes, and microbial growth. By controlling these factors, it is important to develop cost-effective and green solutions to extend the shelf life of agricultural products to reduce waste. At present, the method for preventing fruits from rotting in the market is single, and the method mainly comprises two types of physical corrosion prevention and chemical corrosion prevention. Physical preservation is to prolong the life of fruits by some physical methods, such as vacuum preservation and refrigeration preservation, the former has extremely high requirement on the pressure resistance of container materials, strict requirement on the technology, large investment and high cost, the latter has certain limitations, and for tropical fruits, the tropical fruits are easily frozen at lower temperature, and the refrigeration method needs special equipment and has high economic consumption; chemical preservation is usually preserved by adding food preservatives or manufacturing preservative coating films, and the food preservatives and the preservative coating films have certain toxic and side effects.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a protein anticorrosive coating for fruits and vegetables, which has no toxic or side effect and low cost, and the invention also aims to provide a preparation method of the protein anticorrosive coating.

The technical scheme is as follows: the protein anticorrosive coating for the fruits and the vegetables comprises the following components in percentage by mass of 10-30: 6-8: 2-3: 1-2: 6-8 of egg white, glycerol, an edible hydrophobing agent, an antioxidant and cellulose nanocrystals.

Wherein the edible hydrophobic agent is egg yolk which is rich in fatty acid, and can reduce the hydrophilicity of glycerol and avoid water absorption expansion; the antioxidant is curcumin, tea polyphenol or allicin with the purity of not less than 99.5 percent, can resist external bacteria, fungi and other microorganisms from entering the fruits, can reduce the oxygen content in the microenvironment and is beneficial to the preservation of the fruits.

The preparation method of the protein anticorrosive coating for the fruits and the vegetables is characterized by comprising the following steps of:

(1) preparing cellulose nanocrystals;

(2) dispersing egg white into water, adding glycerol, stirring, adjusting the pH value of the mixed solution to 10-12, and continuously stirring until the mixed solution is uniform;

(3) dispersing an antioxidant in water, adding the antioxidant into the mixed solution obtained in the step (2), and continuously stirring;

(4) and (4) dispersing the cellulose nanocrystals in water, adding the dispersed cellulose nanocrystals into the mixed solution obtained in the step (3), stirring the mixture until the mixture is uniform, and then cooling the mixture to room temperature.

Wherein. The step (1) comprises the following steps:

(11) placing tea stalk powder in a Soxhlet extractor, adding a benzene-alcohol solution for extraction for 6-8 h, and naturally drying for later use;

(12) placing the extracted tea stalk powder in a shaking water bath, adding NaClO₂Mixing the powder with glacial acetic acid until the sample turns white, washing to neutrality, and freeze-drying;

(13) putting the tea stalk powder treated in the step (12) into a KOH solution for water bath treatment, washing to be neutral, and freeze-drying for later use;

(14) and (3) placing the tea stem powder treated in the step (13) in a sulfuric acid solution, uniformly stirring, adding distilled water to terminate the reaction, dialyzing to be neutral to obtain a CNC colloid, centrifugally separating and purifying a sample, and freeze-drying to obtain the cellulose nanocrystal.

Wherein, the benzene-alcohol solution in the step (11) is a toluene/ethanol mixed solution with the volume ratio of 1-2: 1, and the extraction temperature is 90-95 ℃; the water bath temperature in the step (12) is 75-80 ℃, and the tea stem powder and NaClO are₂The usage amount of the powder and the glacial acetic acid is 4 g: 7-9 g: 1mL of NaClO₂Adding the powder and glacial acetic acid into the reaction solution for 5-6 times every 1-2 h, (13) controlling the water bath temperature to be 80-85 ℃, and controlling the use amount of the tea stalk powder and the KOH solution to be 4 g: 100-120 mL of KOH solution, wherein the mass fraction of the KOH solution is 8% -10%; in the step (14), the tea stalk powder is stirred in the sulfuric acid solution at the temperatureThe temperature is 45-50 ℃, the usage amount of the tea stem powder and the sulfuric acid solution is 2 g: 30-40 mL, and the mass percent of the sulfuric acid solution is 63-68%.

Wherein the volume usage amount of the egg white and the water in the step (2) is 1 g: 15-20 mL, using sodium hydroxide pellets when adjusting the pH, stirring at 80-90 ℃, and adding a uniformly dispersed yolk solution into a mixed solution of eggs and glycerol to reduce the hydrophilicity of the glycerol.

The working principle is as follows: the fluidity and flexibility of the protein polymer chains of the eggs are improved, an edible film with medium gas barrier property is formed by drying to block gas, the respiration of fruits in the air is weakened, the intermolecular force of the protein chains can be reduced by glycerol, the fluidity and flexibility of the protein polymer chains are improved, the protein film plasticized by the glycerol can cover objects with irregular shapes, the egg yolks are rich in fatty acid and are hydrophobic substances, the hydrophobicity of the glycerol can be improved, the water absorption expansion of the glycerol is prevented, the sensitivity of materials to water is relieved, and the antioxidant has the characteristics of antibiosis, antifungal and anti-biofilm, can reduce the microbial growth on the surfaces of the fruits and simultaneously reduce O in a microenvironment₂And CO₂The film made of the nano composite material has good mechanical performance, and is proved to be very flexible through uniaxial and biaxial stretching tests, suitable for fruits of different shapes, capable of maintaining the original shape, freshness and antibacterial property in the storage and transportation processes, non-toxic and harmless to a human body, and easy to clean.

Has the advantages that: compared with the prior art, the invention has the following remarkable advantages: 1. the coating can inhibit the growth of microorganisms and simultaneously reduce O in the microenvironment₂And CO₂The good mechanical property, freshness keeping property and antibacterial property of the fruits can be kept; 2. the film formed by the coating has good mechanical properties; 3. the coating is nontoxic and harmless to human bodies, easy to clean and simple to prepare.

Detailed Description

10g of tea stem powder was weighed,wrapping with filter paper, placing in a Soxhlet extractor, adding benzene-alcohol solution at a volume ratio of toluene/alcohol solution of 2: 1, extracting at 95 deg.C for 6 hr, and naturally air drying; placing 4g of the extracted tea stalk powder in a shaking water bath at 75 deg.C, adding 1.5g NaClO every 1h₂And 1mL of glacial acetic acid to remove lignin, repeating for 5-6 times until the sample turns white, washing to be neutral, freeze-drying for later use, placing 4g of the treated tea stem powder in 100mL of KOH solution with the mass fraction of 8%, performing water bath treatment at 80 ℃ for 3h, washing to be neutral by using deionized water, and freeze-drying for later use; 2g of freeze-dried tea stem powder is put into 30mL of sulfuric acid solution with the content of 63 percent, magnetic stirring treatment is carried out at the temperature of 45 ℃, 500mL of distilled water is added to stop the reaction after 125 minutes of reaction, the reaction is dialyzed to be neutral to obtain CNC colloid, a sample is separated and purified by high-speed centrifugation, and the cellulose nanocrystal is obtained by freeze drying.

Weighing 10g of egg white, dispersing into 150mL of deionized water by using a magnetic stirrer, adding 3g of glycerol, stirring for 15min, adding sodium hydroxide pellets to adjust the pH value of the solution to 10, stirring for 15min at 80 ℃, adding 1.5g of egg yolk, continuously stirring for 5min, adding 0.5g of curcumin powder solution, completely dissolving 1.5g of cellulose nanocrystalline powder, adding the solution, continuously stirring for 5min, and cooling to room temperature to obtain the coating material. When in use, the fruits and vegetables are completely immersed in the coating material, then hung for 1 minute, and then immersed in the coating material again, and naturally dried at room temperature. Through experiments, the mass reduction of the mango without the coating is increased by about 60% relative to the mass reduction of the mango after the coating within 20 days, and the surface of the mango without the coating is severely shrunk due to dehydration, while the surface of the mango after the coating is smooth within 20 days; under the same storage condition, the time for the surface of the banana subjected to coating treatment to generate small black spots is 10 days later than that of the banana subjected to uncoated treatment, the banana can be stored for 15 days more, and the area for generating the black spots is small. Therefore, the coating material has better fresh-keeping effect on fruits.

Coli were inoculated on the coating film and over 24h overnight incubation resulted in zero bacterial titer, whereas the blank showed a concentration of colony forming bacteria of over 104-fold. Therefore, the film can effectively inhibit the growth of bacteria on the surface of the fruit.