Hydrophobic BA-coated SiO2 nanoparticle, high-viscosity liquid food anti-sticking coating as well as preparation method and application of high-viscosity liquid food anti-sticking coating

Abstract

The invention belongs to the technical field of new materials and packaging, and discloses a hydrophobic BA-coated SiO2 nanoparticle and high-viscosity liquid food anti-sticking coating and a preparation method and application thereof.The preparation method comprises the following steps that zein and genipin are taken and added into an ethanol solution, oscillation is conducted till the zein and the genipin are completely dissolved, and a Zein-ethanol solution is obtained; adding the hydrophobic BA-coated SiO2 nanoparticles into absolute ethyl alcohol, carrying out ultrasonic treatment until the particles are uniformly distributed, then adding a Zein-ethanol solution, and uniformly mixing to obtain an anti-sticking coating system; and uniformly spraying the anti-sticking coating system onto a clean glass slide by using a handheld spray gun, and drying at room temperature for 5 minutes to obtain the anti-sticking coating. The high-viscosity liquid food anti-sticking coating is prepared through a spraying method, operation is easy, consumed time is short, and the high-viscosity liquid food anti-sticking coating can be simply and conveniently applied to the inner walls of existing food packaging bottles in various shapes. The anti-sticking coating system is sprayed to the surface of a base material through a spray gun, and the high-viscosity liquid food anti-sticking coating can be obtained after room-temperature drying.

Description

Technical Field

[0001] The present invention belongs to the technical fields of new materials and packaging, and in particular relates to a hydrophobic BA@SiO 2 nanoparticle, an anti-sticking coating for high-viscosity liquid foods, and a preparation method and application thereof. Background Art

[0002] Food waste is a global problem. The "Food Waste Index Report 2024" released by the United Nations Environment Programme shows that the total global food waste in 2022 reached 1.05 billion tons, nearly 1 / 5 of the total food available to consumers, and the per capita food waste reached 132 kg. For some non-Newtonian fluid foods, such as yogurt, ketchup, honey, oyster sauce, etc., their high viscosity easily causes part of the food to remain on the inner wall of the packaging container, resulting in food waste. When consumers think the package has been emptied, there is still 3%-10% of the food remaining in it. In addition, food adhesion to the inner wall of the packaging easily leads to the growth of microorganisms, inducing food safety problems; the inability to empty the product in the package will increase the difficulty of packaging recycling. Therefore, preparing an anti-sticking coating for high-viscosity liquid foods using biotoxic-free and environmentally friendly raw materials is of great significance for reducing food resource waste and better ensuring food safety.

[0003] Preparing a hydrophobic coating on the inner surface of packaging materials is an effective method to achieve non-sticking of high-viscosity liquid foods. The preparation of a hydrophobic coating should meet two conditions: one is that the surface contains low-surface-energy substances; the other is that the surface should have a micro-nano rough structure. However, the existing technologies have the following technical problems:

[0004] 1. Toxicity: Fluorides and organosilanes are often used as low-surface-energy modifiers. The hydrophobic coatings prepared therefrom have good hydrophobic effects and good durability. However, such low-surface-energy substances are expensive, and fluorides and their degradation products are harmful to human health and have bioaccumulation, having potential adverse effects on future generations of humans and the environment, and are not suitable for preparing food-contact coatings.

[0005] 2. Complex preparation process: The methods commonly used to construct the rough morphology of the material surface include phase separation method, etching method, mixed coating method, electrospinning method, etc. However, these methods are complex in operation, time-consuming in preparation, and require a flat substrate surface, and are difficult to apply on the inner wall of an irregularly shaped packaging bottle, restricting practical applications.

[0006] 3. Poor adhesion: Currently, there is a hydrophobic coating prepared using natural wax with low surface energy. This coating is safe, non-toxic, and has a simple preparation method. However, natural wax has a low melting point and poor mechanical strength. The coating prepared therefrom has poor adhesion to the substrate, is easy to wear, and the coating is easy to fall off and lose its hydrophobic performance, restricting its practical application in food packaging.

[0007] Therefore, the superposition of these three factors makes it impossible for the prior art to simultaneously meet the requirements of food contact safety, simple process applicability, and coating durability.

[0008] Through retrieval, the following several patent disclosure documents related to this invention patent application were found:

[0009] 1. Comparative Document Patent 1: A special latex for preventing yogurt from sticking to the lid, its preparation method and application (CN105295582A), which prepares a latex with good barrier properties by using a specific formula and process. After coating the yogurt lid, it solves the problem that yogurt easily sticks to the yogurt lid. A variety of organosilicon monomers are used in the raw materials of this formula, such as methylchlorosilane, phenylchlorosilane, methylvinylchlorosilane, etc., which have adverse effects on human health and the environment, and the method has cumbersome steps, complex operations, and a long preparation time.

[0010] The present invention uses natural long-chain fatty acids, silicon dioxide nanoparticles, and zein as raw materials to prepare a strong hydrophobic coating, which is safe, non-toxic, and the raw materials are renewable. The preparation process is simple and time-consuming, and after the hydrophobic suspension is placed for a period of time, it only needs to be homogenized again to achieve the same effect of preventing high-viscosity liquid food from adhering.

[0011] 2. Comparative Document Patent 2: A food-contactable superhydrophobic coating and its preparation method (CN113444451A), which uses shellac, ethyl cellulose, and stearic acid to prepare a mixed solution in absolute ethanol. After the mixed solution is impregnated and coated on the substrate, a coating for preventing liquid food from adhering is formed. This method prepares the coating by the impregnation coating method. Although it can be prepared on various substrates such as glass, paper, and aluminum foil, it requires the substrate to be flat, and it is impossible to determine whether it is applicable to irregularly shaped packaging bottles.

[0012] The present invention adopts the spraying method to prepare the coating, has no requirements for the substrate, and can apply the coating preparation on the surfaces of food packaging bottles of various shapes.

[0013] 3. Comparative Document Patent 3: A method for preparing a transparent superhydrophobic surface using natural wax (CN109593468A), which dissolves Chinese wax and candelilla wax in absolute ethanol to obtain a suspension, and sprays the suspension on the surface of the substrate to obtain a hydrophobic coating. The natural wax used in this method is cheap and renewable, and the preparation method is simple, but there is a problem of poor bonding between the wax coating and the substrate, and it is difficult to be applied to food packaging.

[0014] The present invention constructs a silicon dioxide-based hydrophobic coating with long-chain fatty acids as low surface energy substances and zein as adhesives, which has good bonding properties with various substrates such as glass and PET, and has good anti-sticking effects on various high-viscosity liquid foods such as yogurt, honey, and oyster sauce when applied to the inner wall of the packaging bottle.

[0015] In contrast, this invention patent application is essentially different from the above-mentioned patent publication documents. Summary of the Invention

[0016] The object of the present invention is to overcome the deficiencies in the prior art and provide a hydrophobic BA@SiO 2 nanoparticle, a high-viscosity liquid food anti-sticking coating, and its preparation method and application.

[0017] The technical solution adopted by the present invention to solve its technical problems is:

[0018] A hydrophobic BA@SiO 2 nanoparticle, and the preparation steps of the nanoparticle are as follows:

[0019] Add long-chain saturated fatty acid docosanoic acid BA into absolute ethanol containing 0.01 mol / L HCl, continuously stir in a water bath at 60 °C until completely dissolved, and then add hydrophilic SiO 2 nanoparticles, stir in a water bath at 60 °C for 2 h, dry the obtained solution to constant weight at 50 °C and then anneal at 80 °C for 30 min to obtain hydrophobic SiO 2 nanoparticles modified by long-chain saturated fatty acid, that is, obtain hydrophobic BA@SiO 2 nanoparticles;

[0020] Among them, the ratio of BA: absolute ethanol: hydrophilic SiO 2 nanoparticles in g: mL: g is 4: 100: 2;

[0021] The hydrophilic SiO 2 nanoparticles are a mixture of hydrophilic SiO 2 nanoparticles with a particle size of 15 nm and hydrophilic SiO 2 nanoparticles with a particle size of 50 nm, and the mass ratio of 15-nm hydrophilic SiO 2 nanoparticles: 50-nm hydrophilic SiO 2 nanoparticles is 1: 4;

[0022] A high-viscosity liquid food anti-sticking coating prepared by using the hydrophobic BA@SiO 2 nanoparticles as described above.

[0023] Application of the high-viscosity liquid food anti-sticking coating as described above in food anti-sticking packaging materials.

[0024] Application of the high-viscosity liquid food anti-sticking coating as described above in food anti-sticking packaging bottles.

[0025] Application of the high-viscosity liquid food anti-sticking coating as described above in the anti-sticking packaging of honey, yogurt and oyster sauce.

[0026] The preparation method of the anti-sticking coating for high-viscosity liquid food as described above is as follows:

[0027] Take zein and genipin and add them to an ethanol solution with a volume concentration of 70%. The ratio of zein:genipin:70% ethanol solution in g:g:mL is 2:0.02:5, and shake until the zein is completely dissolved to obtain a zein-ethanol solution; take hydrophobic BA@SiO 2 nanoparticles and add them to absolute ethanol, ultrasonicate for 5 min until the particles are evenly distributed, and then add the zein-ethanol solution. The ratio of hydrophobic BA@SiO 2 nanoparticles:absolute ethanol:zein-ethanol solution in g:mL:mL is 1:20:1.2, and magnetically stir at a speed of 600 rpm until all components are evenly mixed to obtain an anti-sticking coating system; take a hand-held spray gun and evenly spray the anti-sticking coating system onto a clean glass slide, and dry at room temperature for 5 min to obtain an anti-sticking coating for high-viscosity liquid food.

[0028] Furthermore, the nozzle diameter of the spray gun is 0.5 mm, and the perpendicular distance from the spray gun to the substrate during spraying is 20 cm.

[0029] The advantages and positive effects obtained by the present invention are as follows:

[0030] 1. The safe hydrophobic material (wax) used in the prior art cannot stably adhere to the substrate (i.e., the problem of poor adhesion mentioned in the background art) to construct a stable rough hydrophobic structure (i.e., the problem of complex preparation process mentioned in the background art), and other materials in the prior art that can construct a rough hydrophobic structure (i.e., the problem of toxicity mentioned in the background art) have potential safety hazards. The superposition of these three problems makes it impossible for the prior art to simultaneously meet the requirements of food contact safety, simple process applicability, and coating durability. Therefore, the present invention uses biotoxic and environmentally friendly raw materials and prepares an anti-sticking coating for high-viscosity liquid food through a simple process, optimizes the hydrophobic modification effect of long-chain saturated fatty acids on silica nanoparticles, and improves the adhesion of the coating to food packaging materials. Improvements are made in three directions: the selection of modification methods, the optimization of preparation methods, and the improvement of adhesion, and the technical solution of the present invention is obtained.

[0031] 2. The present invention hydrophobically modifies hydrophilic SiO 2 nanoparticles with natural long-chain saturated fatty acids. Compared with the commonly used stearic acid (SA) in the prior art, docosanoic acid (BA) has a better hydrophobic effect. From hydrophobic BA@SiO 2The water contact angle of the coating prepared from nanoparticles can reach 140°. The water contact angle of the anti-sticking coating for high-viscosity liquid foods obtained by adding zein as an adhesive can reach 138.82°, and the water rolling angle can reach 9.79°, showing a nearly super-hydrophobic effect. It has a good anti-sticking effect on high-viscosity liquid foods, and the anti-sticking rates for yogurt, honey, and oyster sauce reach 99%-100%.

[0032] 3. Compared with other hydrophobic coatings, the present invention uses natural long-chain saturated fatty acids, hydrophilic SiO 2 nanoparticles and zein as raw materials, having the advantages of low cost, natural non-toxicity, and no potential harm to the environment and humans.

[0033] 4. The present invention first improves the adhesion between the hydrophobic coating and the substrate by adding zein. The prepared anti-sticking coating for high-viscosity liquid foods has good binding properties with various substrates. The adhesion grade between the coating (m BA :m SiO2 = 1.5:1, v Zein = 6%) prepared with the appropriate formula and the glass slide can reach Grade 4A.

[0034] 5. The anti-sticking coating for high-viscosity liquid foods of the present invention is prepared by spraying method, with simple operation and short time consumption, and can be easily applied to the inner walls of existing food packaging bottles of various shapes. The anti-sticking coating system is sprayed onto the substrate surface by a spray gun, and the anti-sticking coating for high-viscosity liquid foods can be obtained after drying at room temperature for 5 minutes.

[0035] 6. The present invention uses natural long-chain saturated fatty acids as hydrophobic modification substances and zein as an adhesive. All raw materials required for preparing the coating have the advantages of low cost, natural non-toxicity, and no potential harm to the environment and humans. The present invention hydrophobically modifies hydrophilic SiO 2 nanoparticles with natural long-chain saturated fatty acids, and adds zein to improve the adhesion between the coating and the substrate. The coating has low production cost, the raw materials are natural and non-toxic, and there is no potential harm to the environment and humans, and it is a food-contactable coating.

[0036] 7. The present invention adopts the spraying method to construct the rough surface structure required for the hydrophobic coating, with simple operation and short time consumption, without changing the substrate itself, and can be applied to the surfaces of various substrates. The anti-sticking coating system of the present invention is sprayed onto the substrate surface by a spray gun, and the anti-sticking coating for high-viscosity liquid foods can be obtained after drying at room temperature for 5 minutes, and can be easily applied to the inner walls of existing food packaging bottles, including various special-shaped liquid food packaging bottles.

[0037] 8. The adhesion between the hydrophobic coating and the substrate is improved for the first time by adding zein, and the prepared anti-sticking coating for high-viscosity liquid foods has good binding properties with various substrates. In the present invention, zein is used as an adhesive to enhance the adhesion between the coating and the substrate. The hydrophobic region of zein helps to form stable interactions, enabling the protein to effectively bind and maintain the adhesive properties. Zein is dissolved in an alcohol solution, and its adhesive effect can be controlled by adjusting the concentration, which is convenient to apply. The prepared anti-sticking coating for high-viscosity liquid foods has good binding properties with substrates such as PET and glass. Description of the Drawings

[0038] Figure 1 It is the characterization diagram of the hydrophobic SiO 2 nanoparticles in the present invention; wherein, Figure a is the water contact angle of the coating prepared from SiO 2 nanoparticles modified with different long-chain fatty acids; Figure b is the scanning electron micrograph of the coating prepared from SiO 2 nanoparticles modified with different long-chain fatty acids at 5 μm; Figure c is the FTIR diagram of SiO 2 nanoparticles modified with different long-chain fatty acids;

[0039] Figure 2 It is the optimized characterization diagram of the hydrophobic BA@SiO 2 nanoparticles in the present invention; wherein, Figure a is the scanning electron micrograph of the coating prepared from BA@SiO 2 nanoparticles with different particle size combinations at 1 μm; Figure b is the water rolling angle of the coating prepared from BA@SiO 2 nanoparticles with different particle size combinations; Figure c is the water contact angle of the coating prepared from BA@SiO 2 nanoparticles with different particle size combinations;

[0040] Figure 3 It is the characterization diagram of the anti-sticking coating for high-viscosity liquid foods in the present invention, where the modification ratio of BA to SiO 2 nanoparticles is 1.5:1 (m BA :m SiO2 ), and the volume ratio of the added Zein-ethanol solution is 6%; wherein, Figure a is the surface roughness image of the anti-sticking coating for high-viscosity liquid foods; Figure b is the scanning electron micrograph of the anti-sticking coating for high-viscosity liquid foods at 100 μm and 2 μm; Figure c is the FTIR diagram of the anti-sticking coating for high-viscosity liquid foods and each component;

[0041] Figure 4 It is the apparent photograph of the anti-sticking coating for high-viscosity liquid foods prepared on PET cups, glass cups and glass slides in the present invention;

[0042] Figure 5Anti-sticking experiment diagram of the anti-sticking coating for high-viscosity liquid food in the present invention on honey;

[0043] Figure 6 Anti-sticking experiment diagram of the anti-sticking coating for high-viscosity liquid food in the present invention on yogurt;

[0044] Figure 7 Anti-sticking experiment diagram of the anti-sticking coating for high-viscosity liquid food in the present invention on oyster sauce;

[0045] Figure 8 Morphological photos of purified water, yogurt, oyster sauce and honey on the anti-sticking coating for high-viscosity liquid food in the present invention; among them, the upper figure is the top view and the lower figure is the front view. Detailed implementation manners

[0046] The present invention will be further described below in conjunction with embodiments. The following embodiments are narrative and not restrictive, and the protection scope of the present invention cannot be limited by the following embodiments.

[0047] All kinds of experimental operations involved in the specific embodiments are conventional techniques in the art. For the parts not specifically noted in this article, those of ordinary skill in the art can refer to various commonly used reference books, scientific and technological literatures or relevant specifications, manuals, etc. before the application date of the present invention for implementation.

[0048] A hydrophobic BA@SiO 2 nanoparticle, and the preparation steps of the nanoparticle are as follows:

[0049] Add long-chain saturated fatty acid docosanoic acid BA into absolute ethanol containing 0.01 mol / L HCl, continuously stir in a water bath at 60 °C until completely dissolved, and then add hydrophilic SiO 2 nanoparticles, stir in a water bath at 60 °C for 2 h, dry the obtained solution to constant weight at 50 °C and then anneal at 80 °C for 30 min to obtain hydrophobic SiO 2 nanoparticles modified by long-chain saturated fatty acid, that is, obtain hydrophobic BA@SiO 2 nanoparticles;

[0050] Among them, the ratio of BA:absolute ethanol:hydrophilic SiO 2 nanoparticles in g:mL:g is 4:100:2;

[0051] The hydrophilic SiO 2 nanoparticles are a mixture of hydrophilic SiO 2 nanoparticles with a particle size of 15 nm and hydrophilic SiO 2 nanoparticles with a particle size of 50 nm. The hydrophilic SiO 2 nanoparticles with a particle size of 15 nm:hydrophilic SiO 2The mass ratio of the nanoparticles is 1:4;

[0052] Using the hydrophobic BA@SiO 2 nanoparticles to prepare a high-viscosity liquid food anti-sticking coating.

[0053] Application of the high-viscosity liquid food anti-sticking coating as described above in food anti-sticking packaging materials.

[0054] Application of the high-viscosity liquid food anti-sticking coating as described above in food anti-sticking packaging bottles.

[0055] Application of the high-viscosity liquid food anti-sticking coating as described above in the anti-sticking packaging of honey, yogurt and oyster sauce.

[0056] Preparation method of the high-viscosity liquid food anti-sticking coating as described above, the steps are as follows:

[0057] Take zein, genipin and add them to a 70% ethanol solution by volume. The ratio of zein:genipin:70% ethanol solution in g:g:mL is 2:0.02:5, and shake until the zein is completely dissolved to obtain a zein-ethanol solution; Take the hydrophobic BA@SiO 2 nanoparticles and add them to anhydrous ethanol, ultrasonic for 5 min until the particles are evenly distributed, and then add the zein-ethanol solution. The ratio of hydrophobic BA@SiO 2 nanoparticles:anhydrous ethanol:zein-ethanol solution in g:mL:mL is 1:20:1.2, and stir magnetically at a speed of 600 rpm until the components are evenly mixed to obtain an anti-sticking coating system; Take a hand-held spray gun and evenly spray the anti-sticking coating system onto a clean glass slide, and dry it at room temperature for 5 min to obtain a high-viscosity liquid food anti-sticking coating.

[0058] Preferably, the nozzle diameter of the spray gun is 0.5 mm, and the perpendicular distance from the spray gun to the substrate during spraying is 20 cm.

[0059] Specifically, the relevant preparation and detection are as follows:

[0060] A hydrophobic SiO 2 nanoparticle, the preparation steps of the SiO 2 nanoparticle are as follows:

[0061] Add 4 g of long-chain saturated fatty acid to 100 mL of anhydrous ethanol (containing 0.01 mol / L HCl), continuously stir in a 60 °C water bath until completely dissolved, and then add 2 g of hydrophilic SiO 2Nanoparticles were stirred in a water bath at 60 °C for 2 h. The obtained solution was dried to a constant weight at 50 °C and then annealed at 80 °C for 30 min to promote the rearrangement of long-chain saturated fatty acid molecules to form a dense hydrophobic layer, thereby obtaining hydrophobic SiO modified by long-chain saturated fatty acids 2 nanoparticles.

[0062] Among them, the added long-chain saturated fatty acids are myristic acid (MA), palmitic acid (PA), stearic acid (SA), arachidic acid (EA), or behenic acid (BA); the hydrophilic SiO 2 nanoparticles are a mixture of hydrophilic SiO 2 nanoparticles with particle sizes of 15 nm and 50 nm. The mass ratio of 15-nm hydrophilic SiO 2 nanoparticles to 50-nm hydrophilic SiO 2 nanoparticles is 0:1, 1:4, 2:3, 3:2, 4:1, or 1:0.

[0063] Using the hydrophobic SiO 2 nanoparticles described above to prepare a high-viscosity liquid food anti-sticking coating, the preparation method of the anti-sticking coating is as follows:

[0064] Take 10 g of zein, 0.1 g of genipin and add them to 25 mL of a 70% ethanol solution by volume, and shake until the zein is completely dissolved. After standing and reacting at room temperature for 30 min, a zein-ethanol solution is obtained. Take 2 g of hydrophobic BA@SiO 2 nanoparticles and resuspend them in 40 mL of absolute ethanol, and ultrasonicate for 5 min until the particles are evenly distributed to obtain a resuspended BA@SiO 2 -absolute ethanol system, and then add a certain volume ratio of zein-ethanol solution, and magnetically stir at a speed of 600 rpm until all components are mixed evenly, thereby obtaining an anti-sticking coating system. Take a hand-held spray gun and evenly spray the anti-sticking coating system onto a clean substrate, and dry it at room temperature for 5 min to obtain a high-viscosity liquid food anti-sticking coating.

[0065] Among them, the hydrophobic BA@SiO 2 nanoparticles are composed of a mixture of 15-nm and 50-nm SiO 2 nanoparticles with a mass ratio of 1:4. The modification ratio of BA to SiO 2 nanoparticles (refers to the mass ratio of BA to SiO 2 nanoparticles) is 1:1, 1.5:1, 2:1, or 2.5:1 (m BA :m SiO2 ). Add the zein-ethanol solution and the resuspended BA@SiO 2- The volume ratio of the absolute ethanol system (referring to the volume percentage of the total system, i.e., the above-mentioned "40 mL absolute ethanol") is 4%, 6%, 8% or 10%. The nozzle diameter of the spray gun is 0.5 mm, and the perpendicular distance from the substrate during spraying is 20 cm.

[0066] More specific detection and preparation are as follows:

[0067] Example 1 Preparation, optimization and characterization of hydrophobic BA@SiO 2 nanoparticles

[0068] 1. Preparation of hydrophobic SiO 2 nanoparticles

[0069] Add 4 g of long-chain saturated fatty acid to 100 mL of absolute ethanol (containing 0.01 mol / L HCl), continuously stir in a water bath at 60 °C until completely dissolved, and then add 2 g of hydrophilic SiO 2 nanoparticles with a particle size of 15 nm, and stir in a water bath at 60 °C for 2 h. The obtained solution is dried to constant weight at 50 °C and then annealed at 80 °C for 30 min to obtain hydrophobic SiO 2 nanoparticles modified by long-chain saturated fatty acid, specifically MA@SiO 2 nanoparticles, PA@SiO 2 nanoparticles, SA@SiO 2 nanoparticles, EA@SiO 2 nanoparticles, BA@SiO 2 nanoparticles.

[0070] Among them, the added long-chain saturated fatty acids are myristic acid (MA), palmitic acid (PA), stearic acid (SA), arachidic acid (EA) or behenic acid (BA).

[0071] 2. Characterization of hydrophobic SiO 2 nanoparticles

[0072] Take 2 g of hydrophobic BA@SiO 2 nanoparticles and resuspend them in 40 mL of absolute ethanol, and ultrasonicate for 5 min until the particles are evenly distributed to obtain a resuspended BA@SiO 2 - absolute ethanol system. Then take a hand-held spray gun and evenly spray the resuspended BA@SiO 2 - absolute ethanol system onto a clean glass slide, and dry it at room temperature for 5 min to obtain a hydrophobic coating. Use a scanning electron microscope (SEM) to obtain the coating morphology, use Fourier transform infrared spectroscopy (FTIR) to analyze its chemical properties, and measure the water contact angle of the coating. The results are as Figure 1 shown. The present invention optimizes the modification of hydrophilic SiO 2Hydrophobic modification method of nanoparticles. The water contact angle measurement results show that the water contact angle of the coating constructed by MA@SiO 2 nanoparticles is 61.37°, and the water contact angle of the coating constructed by PA@SiO 2 nanoparticles is 113.10°. The water contact angle of the coating constructed by SA@SiO 2 nanoparticles is 122.03°, and the water contact angle of the coating constructed by EA@SiO 2 nanoparticles is 122.53°. The coating constructed by BA@SiO 2 nanoparticles has the best hydrophobicity, and its water contact angle reaches 127.10°( Figure 1 a). As shown in the SEM result diagram, saturated fatty acid-coated SiO 2 nanoparticles form sheet-like or irregular cluster-like protrusions, constructing a micro-nano rough structure( Figure 1 b). The voids in the rough structure of the coating can intercept a large amount of air, making the actual solid-liquid contact area much smaller than the apparent contact area, forming a hydrophobic effect. In the FTIR spectrum, the relatively broad -OH stretching vibration peaks of the modified MA@SiO 2 , PA@SiO 2 , SA@SiO 2 , EA@SiO 2 and BA@SiO 2 nanoparticles at 3432 cm -1 and 1636 cm -1 are significantly weakened, and there is a new absorption peak (ester carbonyl) at 1740 cm -1 , indicating that long-chain saturated fatty acids have been successfully grafted onto SiO 2 nanoparticles( Figure 1 c).

[0073] 3. Optimization and characterization of hydrophobic BA@SiO 2 nanoparticles

[0074] Add 4 g of BA to 100 mL of absolute ethanol (containing 0.01 mol / L HCl), continuously stir in a water bath at 60 °C until BA is completely dissolved, and then add a mixture of SiO 2 nanoparticles with a total mass of 2 g and particle sizes of 15 nm and 50 nm, and stir in a water bath at 60 °C for 2 h. The obtained solution is dried to constant weight at 50 °C and then annealed at 80 °C for 30 min to obtain hydrophobic BA@SiO 2 nanoparticles modified by BA. Resuspend 2 g of BA@SiO 2 nanoparticles in 40 mL of absolute ethanol and ultrasonicate for 5 min until the particles are evenly distributed to obtain a resuspended BA@SiO 2 -absolute ethanol system, and then use a hand-held spray gun to spray the resuspended BA@SiO2 Spray the anhydrous ethanol system evenly onto a clean glass slide and dry it at room temperature for 5 min to obtain a hydrophobic coating.

[0075] Among them, SiO nanoparticles with a total mass of 2 g and particle sizes of 15 nm and 50 nm 2 In the SiO nanoparticle mixture with a particle size of 15 nm 2 The mass ratio of nanoparticles and 50 nm SiO 2 Nanoparticles is 0:1, 1:4, 2:3, 3:2, 4:1 or 1:0. The nozzle diameter of the spray gun is 0.5 mm, and the vertical distance from the substrate during spraying is 20 cm.

[0076] Use a scanning electron microscope (SEM) to obtain the coating morphology, and measure the water contact angle and water rolling angle of the coating. The results are as Figure 2 shown. As shown in the SEM result diagram, in the single-size particle size BA@SiO 2 Coatings (0:1, 1:0 groups), particle agglomeration is likely to occur. The introduction of double-size SiO 2 Nanoparticles (1:4, 2:3, 3:2, 4:1 groups) helps to form a coating surface with a complex rough structure ( Figure 2 a). The measurement results of the water rolling angle and water contact angle show that the water contact angle of the 0:1 group coating is 130.03° and the rolling angle is 13.25°. The water contact angle of the 2:3 group coating is 138.45° and the rolling angle is 11.55°. The water contact angle of the 3:2 group coating is 138.60° and the rolling angle is 15.29°. The water contact angle of the 4:1 group coating is 130.65° and the rolling angle is 21.76°. The water contact angle of the 1:0 group coating is 133.58° and the rolling angle is 22.86°. The water contact angle of the coating prepared from the combination of 15 nm and 50 nm SiO 2 Nanoparticles with a mass ratio of 1:4 reaches a maximum of 139.85° and the rolling angle is minimized to 9.32°, showing the best hydrophobic effect ( Figure 2 b, c). At the same time, it can also be seen that there is a synergistic effect between docosanoic acid and the SiO nanoparticle composition with a mass ratio of 1:4 in the present invention, which can improve the relevant properties of the prepared hydrophobic BA@SiO 2 Nanoparticles. 2

[0077] 4. Selection and Characterization of Adhesive Matrix

[0078] Take 10 g of adhesive matrix and completely dissolve it in 25 mL of 70% ethanol solution by volume to obtain an adhesive-ethanol solution. Take 2 g of hydrophobic BA@SiO 2The nanoparticles were resuspended in 40 mL of absolute ethanol and sonicated for 5 min until the particles were evenly distributed to obtain a resuspended BA@SiO 2 -absolute ethanol system. Then, an adhesive-ethanol solution with a volume ratio (referring to the volume percentage of the total system, i.e., the above-mentioned "40 mL of absolute ethanol". The same applies to the rest of the examples, etc.) of 10% to the resuspended BA@SiO 2 -absolute ethanol system was added, and the mixture was magnetically stirred at 600 rpm until all components were evenly mixed, thus obtaining an anti-sticking coating system. A hand-held spray gun was used to evenly spray the anti-sticking coating system onto a clean glass slide, and after drying at room temperature for 5 min, a high-viscosity liquid food anti-sticking coating was obtained.

[0079] Among them, the binding matrix was zein, ethyl cellulose, shellac or gelatin. The hydrophobic BA@SiO 2 nanoparticles were composed of a mixture of 15 nm and 50 nm SiO 2 nanoparticles with a mass ratio of 1:4. The modification ratio of BA to SiO 2 nanoparticles (referring to the mass ratio of BA to SiO 2 nanoparticles. The same applies to the rest of the examples, etc.) was 2:1 (m BA :m SiO2 ). The nozzle diameter of the spray gun was 0.5 mm, and the perpendicular distance from the spray gun to the substrate during spraying was 20 cm.

[0080] The water contact angles of the above four groups of coatings were measured, and the coating adhesion was measured according to ASTM D3359. The results are shown in Table 1. The water contact angle measurement results showed that the coatings with zein and shellac as the binding matrix had larger water contact angles, which were 126.17° and 125.30° respectively. The coatings with ethyl cellulose and gelatin as the binding matrix had smaller water contact angles, which were 91.15° and 87.90° respectively. The addition of ethyl cellulose and gelatin significantly reduced the hydrophobic properties of the coatings. The adhesion measurement results showed that the coating with ethyl cellulose as the binding matrix had an adhesion grade of 3A, the coating with shellac as the binding matrix had an adhesion grade of 4A, the coating with gelatin as the binding matrix had an adhesion grade of 3A, and the coating with zein as the binding matrix had the highest adhesion grade, reaching 5A.

[0081] Table 1 Water contact angles and adhesion grades of coatings prepared with different binding matrices in the present invention

[0082] Adhesive matrix Zein Ethyl cellulose Shellac Gelatin Water contact angle (°) <![CDATA[126.17±1.42 a > <![CDATA[91.15±0.87 b > <![CDATA[125.30±1.13 a > <![CDATA[87.90±1.87 c > Adhesion grade (A) 5A 3A 4A 3A

[0083] Example 2 Preparation, optimization and characterization of a high-viscosity liquid food anti-sticking coating

[0084] 1. Preparation and optimization of a high-viscosity liquid food anti-sticking coating

[0085] Take 10 g of zein, 0.1 g of genipin, and add them to 25 mL of ethanol solution with a volume concentration of 70%. Shake until the zein is completely dissolved to obtain a zein-ethanol solution. Take 2 g of hydrophobic BA@SiO 2 nanoparticles and resuspend them in 40 mL of absolute ethanol. Ultrasonic for 5 min until the particles are evenly distributed to obtain a resuspended BA@SiO 2 -absolute ethanol system. Then add a zein-ethanol solution with a certain volume ratio to the resuspended BA@SiO 2 -absolute ethanol system. Magnetically stir at a speed of 600 rpm until all components are evenly mixed to obtain an anti-sticking coating system. Take a hand-held spray gun and evenly spray the anti-sticking coating system onto a clean glass slide. After drying at room temperature for 5 min, a high-viscosity liquid food anti-sticking coating is obtained.

[0086] Among them, the hydrophobic BA@SiO 2 nanoparticles are composed of a mixture of 15 nm and 50 nm SiO 2 nanoparticles with a mass ratio of 1:4. The mass ratio of BA to SiO 2 nanoparticles is 1:1, 1.5:1, 2:1, 2.5:1 (m BA :m SiO2 ). The volume ratio of the added zein-ethanol solution to the resuspended BA@SiO 2 -absolute ethanol system is 4%, 6%, 8%, 10%. The nozzle diameter of the spray gun is 0.5 mm, and the perpendicular distance from the spray gun to the substrate during spraying is 20 cm.

[0087] 2. Characterization of the high-viscosity liquid food anti-sticking coating

[0088] Measure the water contact angle and water rolling angle of the above sixteen groups of coatings, and measure the coating adhesion according to ASTM D3359. The results are shown in Table 2. Another high-viscosity liquid food anti-sticking coating with a mass ratio of BA to SiO 2 nanoparticles of 1.5:1 (m BA :m SiO2 ) and a volume ratio of the added zein-ethanol solution to the resuspended BA@SiO 2 -absolute ethanol system of 6% is used. The surface roughness of the coating is measured by a laser confocal microscope, the coating morphology is obtained by SEM, and its chemical properties are analyzed by FTIR. The results are as Figure 3 shown.

[0089] Table 2 Optimization characterization of the high-viscosity liquid food anti-sticking coating in the present invention

[0090]

[0091] Among them, a is the water contact angle of the anti-sticking coating for high-viscosity liquid foods with different formulations; b is the water rolling angle of the anti-sticking coating for high-viscosity liquid foods with different formulations; c is the adhesion grade of the anti-sticking coating for high-viscosity liquid foods with different formulations.

[0092] The results show that when the modification ratio of BA is determined, as the proportion of Zein increases, the water contact angle first increases and then decreases, the water rolling angle shows an increasing trend, and the adhesion grade improves; when the addition ratio of Zein is determined, as the modification ratio of BA increases, the water contact angle shows an increasing trend, the water rolling angle first increases and then decreases, and the adhesion grade decreases (Table 2). In summary, when m BA :m SiO2 is 1.5:1 and the volume ratio of Zein is 6%, the coating has good hydrophobic properties and binding properties with the substrate, the water contact angle reaches 136.60°, the water rolling angle reaches 13.51°, and the adhesion grade reaches 4A level. The results of laser confocal microscopy show that a micron-scale rough structure has been successfully constructed on the surface of the anti-sticking coating, and the average surface roughness is 11.05 μm( Figure 3 a). Combining with the SEM result diagram, the surface of the anti-sticking coating presents irregular flaky protrusions( Figure 3 b). The higher roughness reduces the contact area between the liquid droplet and the coating surface and enhances the hydrophobicity of the coating. In the FTIR spectrum, characteristic absorption peaks of Zein appear at 3315 cm -1 and 1541 cm -1 , indicating that Zein effectively binds to BA@SiO 2 nanoparticles( Figure 3 c). At the same time, it can also be seen that there is a synergistic effect between the mass ratio of BA to SiO 2 nanoparticles of 1.5:1 and the volume ratio of Zein-ethanol solution to the resuspended BA@SiO 2 -anhydrous ethanol system of 6% in the present invention, which can improve the relevant properties of the prepared anti-sticking coating for high-viscosity liquid foods.

[0093] Example 3 Anti-sticking experiment of the anti-sticking coating for high-viscosity liquid foods on honey

[0094] Take 2 g of zein (Zein), add 0.02 g of genipin to 5 mL of ethanol solution with a volume concentration of 70%, and shake until Zein is completely dissolved to obtain a Zein-ethanol solution. Take 1 g of hydrophobic BA@SiO 2The nanoparticles were resuspended in 20 mL of anhydrous ethanol and ultrasonicated for 5 min until the particles were evenly distributed. Then, 1.2 mL of Zein-ethanol solution was added and magnetically stirred at 600 rpm until the components were evenly mixed to obtain an anti-stick coating system. A handheld spray gun was used to evenly spray the anti-stick coating system onto the inner wall of the PET cup. After drying at room temperature for 5 min, a high-viscosity liquid food anti-stick cup was obtained. 5 g of honey was added to the PET cup and the high-viscosity liquid food anti-stick cup, poured for 5 s, and the emptying of the honey was recorded. Among them, the hydrophobic BA@SiO 2 The nanoparticles are composed of 15 nm and 50 nm SiO in a mass ratio of 1:4. 2 Nanoparticle mixture composition: BA and SiO 2 The modification ratio of nanoparticles is 1.5:1 (m BA :m SiO2 ); hydrophobic BA@SiO 2 The other specific steps in the preparation of nanoparticles are the same as those in Example 2. The diameter of the spray gun nozzle is 0.5 mm, and the vertical distance from the substrate during spraying is 20 cm.

[0095] The surface photos of high viscosity liquid food anti-stick coating prepared on PET cups, glass cups and glass sheets are shown in the figure. Figure 4 As shown in the figure, the coating is light yellow and evenly adheres to the PET cup, the inner wall of the glass cup and the surface of the glass sheet. Figure 5 As shown in the figure, after pouring for 5 seconds, the honey in the anti-stick cup is almost completely drained, and the residual amount is less than 1% (m / m), and the honey in the PET cup has 40% (m / m) residual. The high-viscosity liquid food anti-stick coating can effectively prevent honey from sticking. Figure 8 As shown, honey is in a spherical shape on the anti-stick coating of high-viscosity liquid food and rolls off easily.

[0096] Example 4: Experiment on the anti-sticking of high viscosity liquid food anti-stick coating for yogurt

[0097] Take 2g of zein and 0.02g of genipin, add 5mL of 70% ethanol solution, and shake until Zein is completely dissolved to obtain Zein-ethanol solution. 2 The nanoparticles were resuspended in 20 mL of anhydrous ethanol and ultrasonicated for 5 min until the particles were evenly distributed. Then, 1.2 mL of Zein-ethanol solution was added and magnetically stirred at 600 rpm until the components were evenly mixed to obtain an anti-stick coating system. A handheld spray gun was used to evenly spray the anti-stick coating system onto the inner wall of the PET cup. After drying at room temperature for 5 min, a high-viscosity liquid food anti-stick cup was obtained. 5 g of yogurt was added to the PET cup and the high-viscosity liquid food anti-stick cup, poured for 5 s, and the emptying of the yogurt was recorded. Among them, the hydrophobic BA@SiO 2The nanoparticles are composed of a mixture of 15 nm and 50 nm SiO nanoparticles with a mass ratio of 1:4 2 The modification ratio of BA to SiO 2 nanoparticles is 1.5:1 (m BA :m SiO2 ); Other specific steps for preparing the hydrophobic BA@SiO 2 nanoparticles are the same as those in Example 2. The nozzle diameter of the spray gun is 0.5 mm, and the perpendicular distance from the spray gun to the substrate during spraying is 20 cm.

[0098] The anti-sticking experiment results for yogurt are as Figure 6 shown. After pouring for 5 s, all the yogurt in the anti-sticking cup is emptied, and the residue is less than 1% (m / m). 27% (m / m) of the yogurt remains in the PET cup. The anti-sticking coating for high-viscosity liquid foods can effectively prevent yogurt from sticking. As Figure 8 shown, the yogurt forms a spherical shape on the anti-sticking coating for high-viscosity liquid foods and easily rolls off.

[0099] Example 5 Anti-sticking experiment of the anti-sticking coating for high-viscosity liquid foods on oyster sauce

[0100] Take 2 g of zein, 0.02 g of genipin, add them to 5 mL of an ethanol solution with a volume concentration of 70%, and shake until the zein is completely dissolved to obtain a zein-ethanol solution. Take 1 g of hydrophobic BA@SiO 2 nanoparticles and resuspend them in 20 mL of absolute ethanol. Ultrasonic for 5 min until the particles are evenly distributed, then add 1.2 mL of the zein-ethanol solution, and magnetically stir at a rotation speed of 600 rpm until all components are evenly mixed to obtain an anti-sticking coating system. Take a hand-held spray gun and evenly spray the anti-sticking coating system onto the inner wall of a PET cup. After drying at room temperature for 5 min, a high-viscosity liquid food anti-sticking cup is obtained. Add 5 g of oyster sauce to the PET cup and the high-viscosity liquid food anti-sticking cup, pour for 5 s, and record the emptying situation of the oyster sauce. Among them, the hydrophobic BA@SiO 2 nanoparticles are composed of a mixture of 15 nm and 50 nm SiO 2 nanoparticles with a mass ratio of 1:4; The modification ratio of BA to SiO 2 nanoparticles is 1.5:1 (m BA :m SiO2 ); Other specific steps for preparing the hydrophobic BA@SiO 2 nanoparticles are the same as those in Example 2. The nozzle diameter of the spray gun is 0.5 mm, and the perpendicular distance from the spray gun to the substrate during spraying is 20 cm.

[0101] The anti-sticking experiment results for oyster sauce are as Figure 7As shown, almost all the oyster sauce in the anti-sticking cup was emptied after 5 s of pouring, and the residue was less than 1% (m / m). 62% (m / m) of the oyster sauce in the PET cup remained. The anti-sticking coating for high-viscosity liquid foods can effectively prevent sticking of oyster sauce. As Figure 8 shown, the oyster sauce is in a spherical shape on the anti-sticking coating for high-viscosity liquid foods and rolls off easily.

[0102] Although embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the content disclosed in the embodiments.

Claims

1. A hydrophobic BA@SiO2 nanoparticle, characterized in that: The preparation steps of the nanoparticles are as follows: The long-chain saturated fatty acid BA was added to anhydrous ethanol containing 0.01 mol / L HCl, and the mixture was stirred continuously in a water bath at 60°C until it was completely dissolved. Then, hydrophilic SiO2 nanoparticles were added and stirred in a water bath at 60°C for 2 hours. The obtained solution was dried at 50°C to constant weight and then annealed at 80°C for 30 minutes to obtain hydrophobic SiO2 nanoparticles modified with long-chain saturated fatty acids, namely, hydrophobic BA@SiO2 nanoparticles. Among them, the ratio of BA: anhydrous ethanol: hydrophilic SiO2 nanoparticles g: mL: g is 4: 100: 2; The hydrophilic SiO2 nanoparticles are a mixture of hydrophilic SiO2 nanoparticles with a particle size of 15 nm and hydrophilic SiO2 nanoparticles with a particle size of 50 nm, and the mass ratio of the hydrophilic SiO2 nanoparticles with a particle size of 15 nm to the hydrophilic SiO2 nanoparticles with a particle size of 50 nm is 1:

4.

2. A high-viscosity liquid food anti-stick coating prepared using the hydrophobic BA@SiO2 nanoparticles as described in claim 1.

3. Use of the high-viscosity liquid food anti-stick coating as claimed in claim 2 in food anti-stick packaging materials.

4. Use of the high-viscosity liquid food anti-stick coating as claimed in claim 2 in food anti-stick packaging bottles.

5. Application of the high-viscosity liquid food anti-stick coating as claimed in claim 2 in anti-stick packaging of honey, yogurt and oyster sauce.

6. The method for preparing the high-viscosity liquid food anti-stick coating according to claim 2, characterized in that: Here are the steps: Take corn alcohol-soluble protein Zein and genipin and add them to 70% ethanol solution with a volume concentration of Zein: genipin: 70% ethanol solution ratio of g:g:mL being 2:0.02:5, and shake until Zein is completely dissolved to obtain Zein-ethanol solution; take hydrophobic BA@SiO2 nanoparticles and add anhydrous ethanol, ultrasonicate for 5 minutes until the particles are evenly distributed, then add Zein-ethanol solution with a volume concentration of 70% ethanol solution of g:mL:mL being 1:20:1.2, and magnetically stir at 600rpm until the components are evenly mixed to obtain an anti-stick coating system; use a handheld spray gun to evenly spray the anti-stick coating system onto a clean glass slide, and after drying at room temperature for 5 minutes, a high-viscosity liquid food anti-stick coating is obtained.

7. The high-viscosity liquid food anti-stick coating according to claim 6, characterized in that: The nozzle diameter of the spray gun is 0.5 mm, and the vertical distance from the substrate during spraying is 20 cm.

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