Tannin zinc coated feed additive and its preparation method and application

Abstract

The application provides a tannin zinc coated feed additive and a preparation method and application thereof, and belongs to the technical field of livestock feed breeding. Plant raw materials containing tannin are crushed and uniformly mixed with zinc-containing compounds to obtain a plant-zinc-containing compound mixture, the plant-zinc-containing compound mixture is added into a double-screw extruder, and after mixing, shearing and compression, an expanded plant tannin zinc is obtained, the expanded plant tannin zinc is crushed, fluidized, granulated and sprayed with a shellac coating solution, and after drying, the tannin zinc coated feed additive is obtained. The application uses plants containing tannin as raw materials, avoids the complicated process of extracting tannin, utilizes a double-screw extrusion process to accelerate the coordination reaction between tannin in the plants and zinc oxide, and adds the shellac coating solution to realize targeted release of the tannin zinc, improve the bioavailability, and the whole preparation process is environmentally friendly, suitable for large-scale production and commercial utilization.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of livestock feed breeding, and particularly relates to a tannic acid zinc coated feed additive and a preparation method and application thereof. BACKGROUND

[0002] After weaning, various factors can cause diarrhea in piglets, and even a large number of deaths. In the actual feeding process, the stress response of piglets is mainly alleviated by adding antibiotics or high-dose ZnO. However, long-term addition of antibiotics in pig feed will make bacteria gradually adapt and develop drug resistance, resulting in a decrease in the effectiveness of antibiotics, and residual antibiotics may be transmitted to humans through the food chain. Long-term intake of animal source food containing antibiotic residues will have adverse effects on human health. Excessive addition of zinc will cause its accumulation in the animal body, not only transmitting to consumers through meat, but also increasing the discharge of zinc in animal manure, causing pollution to soil, water sources, etc., affecting soil quality and ecological balance. Therefore, under the development background of replacing antibiotics and reducing zinc, it has become a research hotspot in the field of livestock to find safe and green alternative products.

[0003] Tannic acid from natural plants has the effects of anti-stress and improving animal immunity, and zinc tannate, as an organic zinc compound, not only has the biological activity of tannic acid, but also has the nutritional function of zinc, with higher bioavailability and stability, and has potential application value in feed additives. Traditional preparation methods of zinc tannate usually have problems such as complex process, low bioavailability, long reaction time, and introduction of organic solvents. For example, the patent with publication number CN 109820098A discloses an organic zinc feed additive and its preparation method and antibacterial activity application. The organic zinc feed additive is an organic zinc feed additive. The preparation process is to mix tannic acid solution and inorganic zinc solution uniformly, adjust the pH value to 6 by using dilute alkali solution, and react to generate a milky white precipitate. The white precipitate obtained is washed and dried to obtain the organic zinc feed additive. The tannic acid solution used is extracted and prepared from gallnut as raw material. Before preparing the organic zinc feed additive, a separate extraction step of the tannic acid solution is required, which undoubtedly increases the complexity of the process. Moreover, the tannic acid molecule contains multiple active groups such as phenolic hydroxyl groups. In the extraction process, affected by external environmental factors such as temperature, pH value, and light, oxidation, polymerization, and other reactions easily occur, which can destroy the structure of tannic acid, reduce the purity and stability of tannic acid, and the extracted tannic acid solution needs to be stored in the dark to avoid oxidation and reduce activity, thereby reducing the bioavailability. The patent with publication number CN 117143166A discloses a synthesis method of zinc tannate. The method first prepares tannic acid alcohol solution and acidic zinc solution, then mixes and reacts the two to prepare a mixture containing zinc tannate, and then prepares the final product by vacuum distillation, freeze crystallization, centrifugal separation, dissolution, and spray drying. The crystallization mother liquor obtained by vacuum separation can be recycled with the alcohol solution obtained by the first vacuum distillation, which improves the utilization rate of the alcohol solution and reduces the cost and environmental impact. However, the preparation method of zinc tannate has the problems of long reaction time and introduction of organic solvents.

[0004] Therefore, the present application proposes a tannic acid zinc coated feed additive and its preparation method and application. SUMMARY

[0005] In view of the problems of complex preparation process, insufficient synergy, and low bioavailability of existing zinc tannate as a feed additive, the present application proposes a tannic acid zinc coated feed additive and its preparation method and application. High-tannic acid content plants such as gallnut are directly used as the source of tannic acid, and zinc oxide is chemically combined through extrusion and expansion technology, and then coated and granulated with pH-responsive lacquer resin to prepare a feed additive with targeted release capability.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] One of the technical solutions of the present application is:

[0008] A preparation method of a tannin zinc coated feed additive, comprising the following steps:

[0009] The plant containing tannin is crushed and mixed with a zinc compound to obtain a plant-zinc compound mixture;

[0010] The plant-zinc compound mixture is added to a double screw extruder, and after stirring, shearing and compression extrusion, an expanded plant tannin zinc is obtained.

[0011] The expanded plant tannin zinc is crushed, fluidized granulated and sprayed with a shellac coating solution, and after drying, the tannin zinc coated feed additive is obtained.

[0012] Further, the plant raw material containing tannin is selected from gallnuts, and the zinc compound is selected from zinc oxide.

[0013] Further, the mass ratio of tannin content in the plant raw material containing tannin to the zinc compound is 10:1.

[0014] Further, the moisture content of the plant-zinc compound mixture is adjusted to 10-50% before being added to the double screw extruder, preferably to 30%.

[0015] Further, the temperature of the sleeve 1 zone, 2 zone and 3 zone of the double screw extruder is 110℃, and the temperature of the 4 zone, 5 zone and 6 zone is independently selected from 130-170℃, preferably 160℃.

[0016] Further, the rotation speed of the double screw extruder is 40-200r / min, preferably 120r / min.

[0017] Further, the expanded plant tannin zinc is crushed to a mesh size of 5-80 mesh.

[0018] Further, the shellac coating solution is prepared by dissolving shellac resin in ethanol, adding glycerol after dissolution, and mixing, wherein the amount ratio of the shellac resin, ethanol and glycerol is 25g:100mL:1g, and the mass concentration of the ethanol is 95%. The shellac coating solution is used to coat the gallnut expanded material, which has the effects of air tightness, moisture resistance and astringency shielding, and the formed coating is acid resistant, thereby reducing the dissolution and release of the functional component tannin zinc in the additive in the stomach; after the tannin zinc additive enters the duodenum, the additive coating swells and disintegrates under the action of bile, etc., and the tannin zinc in the additive can be quickly dissolved and act on the intestinal mucosa, thereby improving the bioavailability of tannin zinc.

[0019] Further, the airflow temperature is 45 DEG C when spraying the shellac coating solution, the spraying flow rate is 100 kg / h, and the spraying time is 2 h.

[0020] The plant tannin is often in a weakly bound state with polysaccharides, proteins and the like in natural cells and is dispersed and fixed in the plant cells. After the cell structure is destroyed under the action of the double screw high shear, the tannin is released from the complex, the spatial steric hindrance of the phenolic hydroxyl group is reduced, and the active site is more fully exposed. When the plant raw material is crushed and mixed with zinc-containing compounds such as zinc oxide, the hydrophilic groups (such as hydroxyl groups and carboxyl groups) in the cell wall of the plant raw material can wrap the ZnO particles through hydrogen bonding to form a nanoscale dispersion system, avoiding the agglomeration of pure zinc oxide powder. In addition, the polyphenol derivatives (such as gallic acid and catechin) and organic acids (such as malic acid and succinic acid) contained in the plant raw material can act as auxiliary ligands or acid environment regulators. The hydroxyl groups of the polyphenol derivatives can form a "ligand network" with the tannin to stabilize the coordination complex through hydrogen bonding or π-π stacking, reduce the agglomeration or precipitation of Zn 2+ , and the dietary fibers such as cellulose and hemicellulose in the plant form a porous structure in the puffing process to adsorb Zn 2+ as a natural carrier, so that the tannin and Zn 2+ form a "confined reaction environment" in the micropores, shorten the mass transfer distance, increase the local reaction concentration, expand the contact area of the tannin and Zn 2+ , and significantly increase the contact probability of the tannin and Zn 2+ . The fibers in the plant raw material form a porous structure after puffing to provide a network carrier for subsequent fluidized granulation, so that the particle strength of the coordination product (puffed tannin zinc) is higher, and it is easier to form a uniform coating when spraying shellac coating, which indirectly protects the stability of the coordination bond during storage and processing.

[0021] The second technical solution of the present application is:

[0022] A tannin zinc coated feed additive prepared by the method.

[0023] The third technical solution of the present application is:

[0024] The application of the tannin zinc coated feed additive in the preparation of animal feed.

[0025] An exemplary method for preparing a tannin zinc coated feed additive using galls and zinc oxide includes the following steps:

[0026] (1) The galls are crushed, pulverized by a pulverizer, and then passed through a standard test sieve of 60 mesh. Then, the tannin content in the galls is determined, and the galls and zinc oxide are mixed according to a mass ratio of 10:1. After being uniformly mixed, a gall-zinc oxide mixture is obtained, and is stored in a silo in the shade to avoid direct sunlight.

[0027] (2) Adjust the gallnut-zinc oxide mixture to a moisture content of 10-50%, and then put it into a twin-screw extruder, set the rotation speed of the twin-screw extruder to 40-200 r / min, and the temperature of the 1st, 2nd and 3rd zones of the sleeve of the twin-screw extruder to 110℃, and the temperature of the 4th, 5th and 6th zones to be independently selected from 130-170℃, and after mixing, shearing and compression extrusion, obtain the expanded gallnut tannic acid zinc;

[0028] (3) Dissolve 25 g of shellac in 100 mL of 95% ethanol, after dissolving, add 1 g of glycerol to obtain a shellac coating solution;

[0029] (4) Crush the prepared expanded gallnut tannic acid zinc to a mesh size of 5-80 mesh, put it into a fluidized granulator and fluidize it, spray the prepared shellac coating solution from the upper part of the fluidized granulator, the air flow temperature is 45℃, the flow rate is 100 kg / h, the spraying time is 2 h, and after drying and film forming, the product is discharged to obtain a tannic acid zinc coated feed additive.

[0030] In the above preparation process, the coordination principle of tannic acid and zinc oxide (ZnO) is as follows Figure 1 Specifically, the tannic acid contained in gallnut is a macromolecular organic substance containing multiple phenolic hydroxyl groups, and the oxygen atoms in the phenolic hydroxyl groups have lone pair electrons and can participate in coordination. By controlling the water content, the temperature and rotation speed of the twin-screw extruder, partial dissociation of zinc oxide (ZnO) occurs, generating Zn 2+ and O 2- The oxygen atoms of the phenolic hydroxyl groups in the tannic acid molecules then provide their lone pair electrons to the zinc ions dissociated from zinc oxide. The zinc ions have empty orbitals and can accept the lone pair electrons of the oxygen atoms of the phenolic hydroxyl groups, thereby forming coordination bonds. Since tannic acid contains multiple phenolic hydroxyl groups, multiple phenolic hydroxyl groups can coordinate with multiple zinc ions, or one zinc ion can coordinate with multiple phenolic hydroxyl groups in multiple tannic acid molecules, ultimately forming a complex coordination structure. Meanwhile, in the reaction process, the hydrogen atoms on the phenolic hydroxyl groups combine with the oxygen ions dissociated from zinc oxide to generate water, promoting the progress of the coordination reaction.

[0031] The present application uses tannin-containing plants (such as gallnut, etc.) to replace tannic acid. In addition to solving the problem of complex extraction process of tannic acid, the core advantage lies in the use of the natural structural complexity, coexisting component synergy and physical compatibility of plant tannin. Through the crushing-shearing-expansion effect of the twin-screw process, an integrated process of "in-situ release-high efficiency contact-multi-stage coordination" is realized. Compared with pure tannic acid, the plant raw material not only retains the multi-hydroxyl coordination ability of tannin, but also through the auxiliary dissociation of natural ingredients, carrier dispersion and mechanical chemical strengthening, the efficiency of the coordination reaction, the stability of the product and the process economy are significantly improved, and the active loss in the process of separating pure tannin is avoided. It is a coordination reaction promotion strategy with functionality and practicality.

[0032] Compared with the prior art, the present application has the following advantages and technical effects:

[0033] (1) The present application uses plants containing tannic acid as raw materials, which eliminates the cumbersome process of extracting tannic acid. The coordination reaction between tannic acid and zinc oxide in the plants is accelerated under the action of shearing and compression by using a double-screw extrusion process. The addition of a pH-responsive shellac coating solution provides an enteric coating, realizes the targeted release of zinc tannate, improves the bioavailability, and the shellac coating process can further protect the coordination complex, so that it remains stable in the humid, shearing, and collision feed processing environment (such as granulation), avoiding the premature release or degradation of the active ingredients.

[0034] (2) The preparation process of the present application not only improves the bioavailability of zinc and the stability of feed additives, but also eliminates the anti-nutritional side effects of tannic acid, realizes the efficient utilization and targeted release of functional ingredients, has significant advantages in improving animal nutrition absorption and feed quality, the entire preparation process is environmentally friendly, no waste is generated, and is suitable for large-scale production and commercialization. BRIEF DESCRIPTION OF DRAWINGS

[0035] The accompanying drawings, which form a part of this application, are used to provide further understanding of the application, and the illustrative embodiments of the present application and their description serve to explain the present application, and do not constitute an improper limitation of the present application. In the drawings:

[0036] Figure 1 The coordination principle of tannic acid and ZnO in the process of preparing tannic acid zinc-coated feed additives using gallnuts and zinc oxide as examples;

[0037] Figure 2 The processing application diagram of preparing tannic acid zinc-coated feed additives using gallnuts and zinc oxide as examples in the embodiments of the present application;

[0038] Figure 3 The FTIR diagram of zinc oxide, gallnut tannic acid (i.e. raw material gallnut), and expanded gallnut tannic acid zinc in Example 14;

[0039] Figure 4 The SEM diagram of the expanded gallnut tannic acid zinc prepared in Example 14;

[0040] Figure 5 The SEM diagram of the tannic acid zinc-coated feed additive prepared in Example 14. DETAILED DESCRIPTION

[0041] Now, various exemplary embodiments of the present application will be described in detail, which should not be considered as a limitation of the present application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present application.

[0042] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. In addition, where a range of values is provided, it is understood that each intervening value, to the upper and lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of these smaller ranges can independently be included or excluded in the range.

[0043] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All patents, patent applications, publications, and descriptions mentioned herein are incorporated by reference in their entirety for the disclosure and

[0044] Many modifications and variations of the present application described in the specification are possible without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples given are exemplary only. It is to be understood that the application is not limited in scope by the described embodiments.

[0045] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "contains", "containing", or variations thereof, are intended to be open-ended terms that mean including, but not limited to.

[0046] The present application provides a method for preparing a tannin zinc coated feed additive, comprising the following steps:

[0047] The plant containing tannin is crushed and mixed with a zinc compound to obtain a plant-zinc compound mixture;

[0048] The plant-zinc compound mixture is added to a twin-screw extruder, and after shearing, mixing and compression, an expanded plant tannin zinc is obtained.

[0049] The expanded plant tannin zinc is crushed, fluidized granulated and sprayed with a shellac coating solution, and after drying, a tannin zinc coated feed additive is obtained.

[0050] In the preferred embodiments of the present application, the plant raw material containing tannin is gallnut, but is not limited to gallnut, and also includes tara, oak, larch and other plants containing tannin. The zinc compound is zinc oxide, and can also be zinc chloride.

[0051] In the preferred embodiment of the present application, the mass ratio of the tannic acid content in the tannic acid-containing plant raw material to the zinc-containing compound is 10:1, wherein the tannic acid content in the tannic acid-containing plant raw material is determined by a conventional method in the technical field, for example, in the embodiment of the present application, the absorbance value of the tannic acid-containing plant raw material at 276 nm is determined by ultraviolet spectrophotometry, a standard curve is fitted with the absorbance value as the abscissa and the concentration as the ordinate, then the absorbance of the sample is determined and brought into the standard curve to calculate the content.

[0052] In the preferred embodiment of the present application, the water content of the plant-zinc-containing compound mixture is adjusted to 10-50% before being added to the twin-screw extruder, preferably to 30%.

[0053] In the preferred embodiment of the present application, the temperature of the sleeve of the twin-screw extruder in the first zone, the second zone and the third zone is 110°C, and the temperature of the sleeve in the fourth zone, the fifth zone and the sixth zone is independently selected from 130-170°C, preferably 160°C.

[0054] The high-temperature environment (110-170°C) of the twin-screw extruder increases the kinetic energy of tannic acid and zinc oxide molecules, increases the proportion of molecules exceeding the activation energy, and increases the effective collision frequency, thereby accelerating the dissociation of ZnO and the deprotonation of the phenolic hydroxyl group of tannic acid, and promoting the formation of coordination bonds; the high temperature causes the water or polar components (such as natural solvents in plant raw materials) in the material to form a liquid phase environment, accelerating the dissolution and diffusion of Zn 2+ ; the shearing action of the screw in the twin-screw extruder breaks the cell walls in the gallnut, releasing the aggregated tannic acid in the cells and increasing the contact opportunities with Zn 2+ or ZnO; secondly, the high temperature causes the cell wall polysaccharides (cellulose, hemicellulose) of the plant raw material (such as the gallnut) to be disintegrated, serving as a skeleton carrier for the subsequent puffed material.

[0055] In the preferred embodiment of the present application, the rotation speed of the twin-screw extruder is 40-200 r / min, preferably 120 r / min.

[0056] The high shearing force (rotation speed of 40-200 r / min) of the twin screw crushes the plant raw material particles, increases the contact area of the plant raw material with zinc oxide, shortens the mass transfer distance, and fully mixes tannic acid with ZnO at the micro-nano particle or even molecular level; in addition, the shearing force constantly updates the two-phase interface through sliding and friction inside the material, reduces the local concentration gradient, avoids the accumulation of reactants, and ensures that the coordination reaction proceeds uniformly in the whole material. High shearing force also induces mechanical chemical action, changes the polarity of the defects on the surface of ZnO or the molecular bonds of tannic acid through stress, reduces the reaction activation energy, and further accelerates the coordination reaction.

[0057] In the preferred embodiment of the present application, the expanded plant tannic acid zinc is crushed to a mesh size of 5-80 mesh.

[0058] In the preferred embodiment of the present application, the shellac coating solution is prepared by dissolving shellac resin in ethanol, and then adding glycerol to the solution, wherein the ratio of the amounts of shellac resin, ethanol and glycerol is 25 g:100 mL:1 g, and the mass concentration of ethanol is 95%.

[0059] In the preferred embodiment of the present application, the air flow temperature during spraying of the shellac coating solution is 45℃, the flow rate during spraying is 100 kg / h, and the spraying time is 2 h.

[0060] The present application also provides a tannic acid zinc coated feed additive prepared by the above method.

[0061] An exemplary method for preparing a tannic acid zinc coated feed additive using gallnuts and zinc oxide includes the following steps:

[0062] (1) The gallnuts are crushed, and then passed through a standard test sieve with a mesh size of 60 mesh. The tannic acid content in the gallnuts is then determined. The gallnuts and zinc oxide are mixed in a mass ratio of 10:1, and then uniformly mixed to obtain a gallnut-zinc oxide mixture, which is then stored in an intermediate bin;

[0063] (2) The gallnut-zinc oxide mixture is adjusted to a moisture content of 10-50%, and then fed into a double-screw extruder. The rotation speed of the double-screw extruder is set to 40-200 r / min. The temperatures of the 1st, 2nd and 3rd zones of the double-screw extruder sleeve are all 110℃, and the temperatures of the 4th, 5th and 6th zones are independently selected from 130-170℃. After stirring and extrusion, an expanded gallnut tannic acid zinc is obtained.

[0064] (3) 25 g of shellac is dissolved in 100 mL of 95% ethanol, and then 1 g of glycerol is added to obtain a shellac coating solution;

[0065] (4) The expanded gallnut tannic acid zinc prepared in the above step is crushed to a mesh size of 5-80 mesh, and then fed into a fluidized granulator. The shellac coating solution prepared in the above step is sprayed from the upper part of the fluidized granulator at an air flow temperature of 45℃ and a flow rate of 100 kg / h for 2 h. After drying and film formation, the tannic acid zinc coated feed additive is obtained.

[0066] The tannic acid zinc coated feed additive prepared in the embodiment of the present application can be used to prepare piglet feed.

[0067] The processing and application diagram of the tannic acid zinc coated feed additive prepared using gallnuts and zinc oxide as an example in the embodiment of the present application is shown in Figure 2 .

[0068] The gallnut used in the embodiments of the present application is purchased from Wufeng Chongxin Biological Technology Co., Ltd., and the zinc oxide, glycerol and shellac are commercially available, wherein the shellac is purchased from Anning Daike Fine Chemical Co., Ltd.

[0069] The technical solutions of the present application are further described below through examples.

[0070] Example 1

[0071] (1) The gallnut is crushed, and after being crushed by a crusher, it is passed through a standard test sieve of 60 meshes, and then the tannic acid content in the gallnut is determined, and the gallnut-zinc oxide mixture is prepared according to the mass ratio of tannic acid to zinc oxide of 10:1, and is uniformly mixed and then stored in the dark;

[0072] (2) The gallnut-zinc oxide mixture is adjusted to a moisture content of 30%, and then is put into a double-screw extruder, and the rotation speed of the double-screw extruder is set to 80 r / min, and the temperatures of the 1st zone, 2nd zone and 3rd zone of the sleeve of the double-screw extruder are all 110°C, and the temperatures of the 4th zone, 5th zone and 6th zone are all 140°C, and after stirring and extruding, the expanded gallnut tannic acid zinc is obtained, and after the coordination of tannic acid and zinc oxide, a product that is not easy to water is generated, and the index results are shown in Table 1.

[0073] Example 2

[0074] The same as Example 1, except that the gallnut-zinc oxide mixture is adjusted to a moisture content of 10%, and the index results are shown in Table 1.

[0075] Example 3

[0076] The same as Example 1, except that the gallnut-zinc oxide mixture is adjusted to a moisture content of 20%, and the index results are shown in Table 1.

[0077] Example 4

[0078] The same as Example 1, except that the gallnut-zinc oxide mixture is adjusted to a moisture content of 40%, and the index results are shown in Table 1.

[0079] Example 5

[0080] The same as Example 1, except that the gallnut-zinc oxide mixture is adjusted to a moisture content of 50%, and the index results are shown in Table 1.

[0081] Table 1 Index of gallnut tannic acid zinc expanded material prepared at different moisture contents in Examples 1-5

[0082]

[0083] Example 6

[0084] (1) The gallnut is broken, crushed by a pulverizer, and then passed through a standard test sieve of 60 mesh. Then the tannic acid content in the gallnut is measured. The gallnut-zinc oxide mixture is prepared by mixing the tannic acid and zinc oxide in a mass ratio of 10:1, and then uniformly mixing and storing in the dark;

[0085] (2) The gallnut-zinc oxide mixture is adjusted to a moisture content of 30%, and then put into a twin-screw extruder. The rotation speed of the twin-screw extruder is set to 40 r / min. The temperatures of the 1st zone, 2nd zone and 3rd zone of the sleeve of the twin-screw extruder are all 110°C, and the temperatures of the 4th zone, 5th zone and 6th zone are all 140°C. After stirring and extruding, the expanded gallnut tannic acid zinc is obtained. The index results are shown in Table 2.

[0086] Example 7

[0087] The same as Example 6, except that the rotation speed of the twin-screw extruder is set to 120 r / min. The index results are shown in Table 2.

[0088] Example 8

[0089] The same as Example 6, except that the rotation speed of the twin-screw extruder is set to 160 r / min. The index results are shown in Table 2.

[0090] Example 9

[0091] The same as Example 6, except that the rotation speed of the twin-screw extruder is set to 200 r / min. The index results are shown in Table 2.

[0092] Table 2 Indexes of the expanded gallnut tannic acid zinc prepared at different rotation speeds

[0093]

[0094] Example 10

[0095] (1) The gallnut is broken, crushed by a pulverizer, and then passed through a standard test sieve of 60 mesh. Then the tannic acid content in the gallnut is measured. The gallnut-zinc oxide mixture is prepared by mixing the tannic acid and zinc oxide in a mass ratio of 10:1, and then uniformly mixing and storing in the dark;

[0096] (2) The gallnut-zinc oxide mixture is adjusted to a moisture content of 30%, and then put into a twin-screw extruder. The rotation speed of the twin-screw extruder is set to 120 r / min. The temperatures of the 1st zone, 2nd zone and 3rd zone of the sleeve of the twin-screw extruder are all 110°C, and the temperatures of the 4th zone, 5th zone and 6th zone are all 150°C. After stirring and extruding, the expanded gallnut tannic acid zinc is obtained. The index results are shown in Table 3.

[0097] Example 11

[0098] The same as example 10, the only difference is that the temperature of 4, 5 and 6 zones is 160℃, and the index results are shown in Table 3.

[0099] Example 12

[0100] The same as example 10, the only difference is that the temperature of 4, 5 and 6 zones is 170℃, and the index results are shown in Table 3.

[0101] Example 13

[0102] The same as example 10, the only difference is that the temperature of 4, 5 and 6 zones is 180℃, and the index results are shown in Table 3.

[0103] Table 3 Index of the expanded gallnut tannic acid zinc prepared at different temperatures

[0104]

[0105] Performance test

[0106] The high degree of expansion means that more porous structure is formed inside the particles, the specific surface area is significantly increased, which can accelerate the dissolution and release of zinc tannate in the animal intestine, improve the bioavailability of zinc tannate, the pores as material transmission channels can regulate the release rate of zinc tannate, avoid premature release in the stomach acid environment, ensure its gradual release in the intestinal alkaline environment, and improve the targeting. As can be seen from Tables 1-3, during the preparation of the expanded gallnut tannic acid zinc, the water content of the gallnut-zinc oxide mixture is 30%, the screw rotation speed is 120 r / min, and the temperatures of 4, 5 and 6 zones are 160℃, the degree of expansion of the expanded gallnut tannic acid zinc is the best, and the pore distribution is uniform. Based on the above optimal conditions, the preparation of the tannic acid zinc coated feed additive is carried out.

[0107] Example 14

[0108] A preparation method of a tannic acid zinc coated feed additive, comprising the following steps:

[0109] (1) The gallnut is crushed, crushed by a crusher and then passed through a standard test sieve of 60 mesh, and then the tannic acid content in the gallnut is determined. The gallnut-zinc oxide mixture is prepared according to the mass ratio of tannic acid to zinc oxide of 10:1, uniformly mixed and then stored in the dark;

[0110] (2) The water content of the gallnut-zinc oxide mixture is adjusted to 30%, and then it is put into a double screw extruder. The rotation speed of the double screw extruder is set to 120 r / min, the temperatures of 1, 2 and 3 zones of the sleeve of the double screw extruder are all 110℃, and the temperatures of 4, 5 and 6 zones are all 160℃. After stirring and extrusion, the expanded gallnut tannic acid zinc is obtained (the FTIR graphs of zinc oxide, gallnut tannic acid (i.e. raw material gallnut) and expanded gallnut tannic acid zinc are shown in Figure 3, SEM of the expanded zinc gallate tannin acid is shown in Figure 4 );

[0111] (3) The shellac was dissolved in 95wt% ethanol, and glycerol was added after dissolution to obtain a shellac coating solution, wherein the amount ratio of shellac resin, ethanol and glycerol was 25g: 100mL: 1g;

[0112] (4) The prepared expanded zinc gallate tannin acid was crushed to 8 mesh, and was put into a fluidized granulator and fluidized, and the prepared shellac coating solution was sprayed from the upper part of the fluidized granulator, the air flow temperature was 45°C, the flow rate was 100kg / h, the spraying time was 2h, and the material was discharged after drying and film forming, to obtain a zinc tannin acid coated feed additive (SEM is shown in Figure 5 ).

[0113] From Figure 3 it can be seen that the Zn-O bond vibration is at 559cm -1 . The -OH stretching vibration of gallate tannin acid is in the range of 3500-3200cm -1 , which is a wide peak, which may be related to intermolecular hydrogen bonding. The C=O stretching vibration is at 1718cm -1 , and the characteristic peaks of the benzene ring are at 1612, 1530 and 1448cm -1 , respectively. After coordination with zinc oxide, the characteristic absorption peaks of gallate tannin acid are shifted, such as the C=O peak moving from 1718cm -1 to about 1703cm -1 , which is because the change in electron cloud density leads to a decrease in bond energy, which further supports the coordination effect.

[0114] From Figure 4 and Figure 5 it can be seen that the expanded product, expanded zinc gallate tannin acid, has a loose and porous structure, which is conducive to the release of zinc gallate tannin acid, and after the expanded particles are coated with shellac resin, a layer of film is formed on the surface, forming a relatively smooth surface.

[0115] Comparative Example 1

[0116] (1) The galla was crushed, crushed by a crusher and then passed through a standard test sieve of 60 mesh, and then the tannin acid content in the galla was determined, and the galla-zinc oxide mixture was prepared according to the mass ratio of tannin acid to zinc oxide of 10:1, and was mixed uniformly and then stored in the dark;

[0117] (2) The shellac was dissolved in 95wt% ethanol, and glycerol was added after dissolution to obtain a shellac coating solution, wherein the amount ratio of shellac resin, ethanol and glycerol was 25g: 100mL: 1g;

[0118] (3) The prepared gallnut-zinc oxide mixture is mixed and crushed to 8 mesh, and is put into a fluidized granulator and fluidized. The prepared shellac coating solution is sprayed from the upper part of the fluidized granulator, the air flow temperature is 45°C, the flow rate is 100 kg / h, the spraying time is 2 h, and the material is discharged after drying and film forming to obtain tannic acid zinc coated feed additive.

[0119] Performance test

[0120] The tannic acid zinc coated feed additive prepared in Example 14 and Comparative Example 1 is respectively added to the piglet daily ration at an addition amount of 1%, and two groups of controls are set up, in which equal amounts of gallnut and zinc oxide are respectively used instead of the tannic acid zinc coated feed additive to be added to the piglet daily ration. The specific composition of the piglet daily ration is corn-soybean meal type daily ration, and the specific components are shown in Table 4:

[0121] Table 4 Composition and nutritional level of corn-soybean meal type daily ration

[0122] Raw materials Proportion / % Raw materials Proportion / % Corn 65 Salt 0.3 Soybean meal 22 Lysine 0.15 Bran 5 Methionine 0.05 Stone powder 1.2 Premix 1.5 Dicalcium phosphate 0.8 Soybean oil 4

[0123] The above obtained piglet daily ration is used as feed to feed piglets, and the specific method is as follows:

[0124] Please supplement the other parameters such as feeding amount, feeding time, feeding frequency, management during feeding, piglet days, piglet initial weight, etc.

[0125] After 21 days of feeding, the growth performance, stress and immune performance, intestinal health performance, oxidation and residual performance are tested, wherein:

[0126] Feed conversion rate (FCR) = total feed consumption / total weight gain of animals;

[0127] Diarrhea rate (%) = number of diarrhea pigs per treatment / total number of pigs per treatment x 100;

[0128] The serum cortisol test is carried out by enzyme-linked immunosorbent assay, and the color is developed by enzyme reaction for quantitative determination;

[0129] The immunoglobulin IgG test is carried out by enzyme-linked immunosorbent assay, and the enzyme-labeled antibody is combined with IgG, and the color is developed by reaction for quantitative determination;

[0130] The villus height / crypt depth ratio test is carried out by HE staining method to prepare tissue sections of duodenum, jejunum and ileum tissue samples, and the villus height, crypt depth and villus / crypt ratio (villus height / crypt depth) are measured and calculated under an optical microscope;

[0131] The number of lactic acid bacteria is counted by colony counting method, the lactic acid bacteria are separated by culture medium, and the number of viable bacteria is counted by colony forming units; the serum MDA is tested by enzyme-linked immunosorbent assay, the anti-MDA specific antibody is used, and the serum MDA concentration is detected by competition method;

[0132] Fecal zinc residue was determined by direct determination of zinc ion content using a plasma mass spectrometer.

[0133] The results of the performance tests are shown in Table 5.

[0134] The results of the performance tests are shown in Table 5.

[0135]

[0136] Note: ↑ indicates that the higher the value is, the better; ↓ indicates that the lower the value is, the better

[0137] As can be seen from Table 5, the tannic acid zinc coated feed additive of the present application significantly improves the anti-diarrhea effect, which is increased by 65% compared with the control group (pomegranate), increased by 55.79% compared with the control group (zinc oxide), and increased by 52.81% compared with the simple mixture of pomegranate and zinc oxide. It is shown that the method of the present application accelerates the coordination reaction of tannic acid and zinc oxide in pomegranate, realizes the improvement of the bioavailability of zinc and the stability of the feed additive; in addition, the tannic acid zinc coated feed additive of the present application also has an intestinal protection effect and improves the intestinal morphology through the slow-release property, which is superior to the single component of the control group; finally, the tannic acid zinc coated feed additive of the present application has an environmental protection and safety effect, reduces the zinc residue, and reduces environmental pollution.

[0138] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any change or replacement easily thought of by those skilled in the art within the technical range disclosed by the present application should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A process for the preparation of a tannin zinc coated feed additive, characterized by, The method comprises the following steps: The tannin-containing plant raw material is crushed and mixed with a zinc-containing compound to obtain a plant-zinc-containing compound mixture; The plant-zinc-containing compound mixture is added into a double-screw extruder, and then mixed, sheared and compressed to obtain expanded plant tannin zinc; The expanded plant tannin zinc is crushed, fluidized, granulated and sprayed with a shellac coating solution, and then dried to obtain the tannin zinc coated feed additive; The tannin-containing plant raw material is selected from gallnuts; and the zinc-containing compound is selected from zinc oxide; The temperature of the double-screw extruder sleeve is 110℃ in the first, second and third zones, and 130-170℃ in the fourth, fifth and sixth zones; The shellac coating solution is prepared by dissolving shellac resin in ethanol, adding glycerol after dissolution, and then mixing, wherein the amount ratio of the shellac resin, ethanol and glycerol is 25g:100mL:1g.

2. The process for the preparation of tannin zinc coated feed additive as claimed in claim 1 wherein, The mass ratio of the tannin content in the tannin-containing plant raw material to the zinc-containing compound is 10:

1.

3. The process for the preparation of tannin zinc coated feed additive as claimed in claim 1 wherein, The water content of the plant-zinc-containing compound mixture is 10-50%.

4. The method of claim 1, wherein the tannin acid zinc-coated feed additive is prepared by the steps of: The rotation speed of the double-screw extruder is 40-200r / min. ​ 5. The process for the preparation of tannin zinc coated feed additive as claimed in claim 1 wherein, The airflow temperature during the spraying of the shellac coating solution is 45℃, the spraying flow rate is 100kg / h, and the spraying time is 2h. 6.A tannin zinc coated feed additive prepared by the preparation method of any one of claims 1-5. 7.Use of the tannin zinc coated feed additive of claim 6 in the preparation of animal feed.

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