Preparation method of organic acid coated tryptophan pellet feed

Abstract

The invention provides a preparation method of organic acid coated tryptophan pellet feed, and belongs to the technical field of feed. The preparation method comprises the following steps: preparing tryptophan thick slurry, preparing a core material, preparing a modified core material, preparing a wall material and coating. The step of preparing the wall material comprises the following steps: performing melting treatment on organic acid, uniformly stirring, cooling, and performing fluidization treatment to obtain the wall material; the organic acid is two or more of formic acid, benzoic acid, lactic acid, citric acid, sorbic acid, lauric acid, propionic acid and acetic acid; according to the tryptophan pellet feed prepared by the method disclosed by the invention, the organic acid coating layer is uniform and is not easy to fall off, and the tryptophan is good in stability, good in palatability and high in bioavailability.

Description

Technical Field

[0001] The invention belongs to the technical field of feed, and in particular relates to a method for preparing tryptophan granular feed coated with organic acid. Background Art

[0002] In recent years, with the development of animal husbandry and feed industry, the application of low-protein diets and unconventional protein feed raw materials has received increasing attention; in compound feeds, the widespread use of synthetic amino acids such as methionine and lysine has made tryptophan the main limiting amino acid in the diet.

[0003] Tryptophan, also known as β-indolylalanine, is an amino acid necessary for animal growth. It participates in the synthesis of protein in animals and is crucial to their growth and development. Tryptophan is a precursor of serotonin and melatonin, which can regulate animals' emotions, appetite and sleep, thereby affecting their growth performance. It can also participate in the regulation of the immune system, enhancing the animals' immune function and disease resistance. In the animal breeding process, adding an appropriate amount of tryptophan can improve the conversion rate of feed, balance the amino acid ratio, and reduce feed costs. It is an important measure to meet the nutritional needs of animals and promote their healthy growth.

[0004] However, tryptophan is easily degraded by light, heat, oxygen, humidity, etc. during feed processing and storage, resulting in the loss of its effective ingredients and increasing the amount of tryptophan added to the feed. In addition, tryptophan has poor palatability, which affects the animal's feeding. It is easily destroyed in the animal's digestive tract and has a low absorption rate.

[0005] With the ban on the use of antibiotics as animal growth promoters in the EU and other regions, as well as concerns about pathogen resistance and drug residues, growth-promoting antibiotic feed additives have been widely banned in commercial feeds. In this context, organic acids, as a safe and efficient alternative, can effectively inhibit the growth of mold and bacteria in feed, prevent feed from mold and deterioration, and can also regulate the balance of gastrointestinal flora, thereby improving the gastrointestinal health of animals. They can also enhance the activity of digestive enzymes, promote the digestion and absorption of proteins, fats and minerals, and improve the utilization rate of feed. In addition, by improving the intestinal environment and nutrient absorption, they can improve the growth performance and immunity of animals. Therefore, the current research focus is to use organic acid coating technology to coat a layer of organic acid on the surface of tryptophan. It can not only solve the problems of poor stability and low bioavailability of tryptophan, but also further promote the growth performance of animals by regulating intestinal flora and improving palatability.

[0006] However, traditional coating methods usually result in uneven organic acid coating layers, which leads to incomplete coating of some tryptophan, and the tryptophan is still easily damaged by the external environment. During feed processing and storage, the organic acid coating layer is easy to fall off, thereby affecting the stability of tryptophan. In addition, in the gastrointestinal tract of animals, the coating layer has an unstable rate and dissolves too early or too late, affecting the effective release and absorption of tryptophan.

[0007] Therefore, a method for preparing an organic acid-coated tryptophan granular feed is provided, so that the organic acid coating layer is uniform and not easy to fall off, and tryptophan can be accurately released in the gastrointestinal tract of animals, thereby significantly improving the stability, bioavailability and palatability of tryptophan, and improving animal immunity has become a technical problem that needs to be solved urgently. Summary of the invention

[0008] In order to solve the technical problems existing in the prior art, the present invention provides a method for preparing an organic acid-coated tryptophan granular feed, wherein the organic acid coating layer is uniform and not easy to fall off, and the tryptophan has good stability, good palatability and high bioavailability.

[0009] In view of the above technical problems, the present invention adopts the following technical solutions: A method for preparing tryptophan pellet feed coated with an organic acid, comprising the steps of preparing tryptophan concentrated slurry, preparing core material, preparing modified core material, preparing wall material and coating, and the specific operations are as follows: 1. Preparation of Tryptophan Concentrate The fermentation broth is inactivated in an environment of 60-85°C and pH 3.0-5.0 for 5-20 minutes, and then evaporated at 60-110°C to obtain a tryptophan concentrate. The solid content of the tryptophan concentrate is controlled to be 30-40wt%, and the tryptophan content is 10-20wt% of the total amount of the tryptophan concentrate.

[0010] 2. Preparation of core material The tryptophan slurry is dried to obtain crude tryptophan, the crude tryptophan is mixed with 2-3 times the mass of deionized water, stirred evenly, and then shot blasted to obtain micro-pellets, the micro-pellets are sieved to control the micro-pellets to be 1-10 mm, and then dried at 40-90° C. for 30-120 min to obtain the core material.

[0011] 3. Preparation of modified core material (1) Composite The core material is placed in anhydrous ethanol, stirred evenly, and then ethyl orthosilicate is slowly added, and the addition amount is controlled to be 0.20-0.25 g / min. Stirring is performed while adding, and the stirring speed is controlled to be 200-220 rpm. After the addition is completed, an ammonia solution is added, and the reaction is stirred at 30-35° C. for 3.7-4.5 hours. After the stirring reaction is completed, centrifuge at 3800-4200 rpm for 10-15 minutes to obtain a solid, and after washing, vacuum drying is performed at 50-54° C. for 2.7-3.2 hours to obtain a primary modified core material; The mass ratio of the core material, anhydrous ethanol, tetraethyl orthosilicate and ammonia solution is 8.0-12.0:52-68:5.0-6.4:2.5-3.0; The mass concentration of the ammonia solution is 18-22%; (2) Modification Put hydroxyethyl cellulose into isopropanol, stir evenly, add β-glucan and primary modified core material, raise the temperature to 36-40°C, keep stirring for 1.3-1.6h, then add chitosan and functionalized locust bean gum, continue to raise the temperature to 56-60°C, stir at 240-260rpm for 4.8-5.2h, and after stirring, dry to obtain modified core material; The mass ratio of the hydroxyethyl cellulose, isopropanol, β-glucan, primary modified core material, chitosan and functionalized locust bean gum is 1.4-1.8:100:1.2-1.5:18.0-19.0:2.0-2.3:1.1-1.4; The preparation method of the functionalized locust bean gum comprises the following steps: adding locust bean gum to deionized water, and after the locust bean gum is completely dissolved, adding potassium periodate and stirring evenly, reacting in a light-proof environment at a reaction temperature of 30-34° C. and a reaction time of 2.8-3.2 h. After the reaction is completed, dialyzing and freeze-drying are performed to obtain the functionalized locust bean gum; The mass ratio of the deionized water, locust bean gum and potassium periodate is 100:1.8-2.2:2.3-2.7.

[0012] 4. Preparation of wall materials The organic acid is mixed evenly, heated to a molten state at a rate of 0.8-1.2°C / min, stirred evenly, cooled at 40-60°C, and then fluidized. The inlet air temperature of the fluidized bed is 30-60°C, and the outlet air temperature is 25-45°C. After the fluidization treatment, the wall material is obtained; The organic acid is two or more of formic acid, benzoic acid, lactic acid, citric acid, sorbic acid, lauric acid, propionic acid and acetic acid.

[0013] 5. Encapsulation The modified core material is added to the wall material, stirred evenly, and then subjected to ultrasonic treatment, the ultrasonic time is 1.2-1.8h, the ultrasonic power is 160-170W, and the ultrasonic frequency is 35-40kHz. After the ultrasonic treatment, the organic acid-coated tryptophan granular feed is obtained by granulation and drying; The mass ratio of the modified core material to the wall material is 1:2.0-4.0.

[0014] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. The tryptophan pellet feed prepared by the method of the present invention has a rumen passing rate of 0 at 0h, 95.6-98.7% at 2h, 84.2-87.4% at 6h, and 75.3-78.1% at 12h in a simulated rumen digestion test; 2. In a simulated duodenal digestion test, the tryptophan granular feed prepared by the method of the present invention has a small intestinal release rate of 26.4-28.9% at the 2nd hour, a small intestinal release rate of 49.1-51.5% at the 6th hour, a small intestinal release rate of 63.4-65.2% at the 10th hour, a small intestinal release rate of 69.8-72.4% at the 12th hour, and a small intestinal release rate of 97.4-98.5% at the 24th hour. DETAILED DESCRIPTION

[0015] In order to more clearly understand the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described.

[0016] Example 1 1. Preparation of Tryptophan Concentrate The fermentation broth was inactivated in an environment of 60°C and pH 3.0 for 20 minutes to obtain a tryptophan concentrate. The solid content of the tryptophan concentrate was controlled to be 30wt%, and the tryptophan content was 10wt% of the total amount of the tryptophan concentrate.

[0017] 2. Preparation of core material The tryptophan slurry is dried to obtain crude tryptophan, the crude tryptophan is mixed with deionized water of twice its mass, stirred evenly, and then shot blasted to obtain micro-pellets, the micro-pellets are sieved to control the micro-pellets to be 1 mm, and then dried at 40° C. for 120 min to obtain the core material.

[0018] 3. Preparation of modified core material (1) Composite 8.0 g of core material was placed in 52 g of anhydrous ethanol, and after stirring evenly, 5.0 g of tetraethyl orthosilicate was slowly added, and the addition amount was controlled to be 0.20 g / min. Stirring was performed while adding, and the stirring speed was controlled to be 200 rpm. After the addition was completed, 2.5 g of ammonia solution was added, and the reaction was stirred at 30°C for 4.5 hours. After the stirring reaction was completed, the solid was centrifuged at 3800 rpm for 15 minutes to obtain a solid. After washing, it was vacuum dried at 50°C for 3.2 hours to obtain a primary modified core material; The mass concentration of the ammonia solution is 18%; (2) Modification 1.4 g of hydroxyethyl cellulose was added to 100 g of isopropanol, and after being stirred evenly, 1.2 g of β-glucan and 18.0 g of primary modified core material were added, the temperature was raised to 36°C, and the mixture was stirred for 1.3 h. Then, 2.0 g of chitosan and 1.1 g of functionalized locust bean gum were added, the temperature was further raised to 56°C, and the mixture was stirred at 240 rpm for 5.2 h. After the stirring was completed, the mixture was dried to obtain a modified core material. The preparation method of the functionalized locust bean gum comprises the following steps: adding 1.8 g of locust bean gum to 100 g of deionized water, and after the gum is completely dissolved, adding 2.3 g of potassium periodate and stirring evenly, reacting the mixture in a light-proof environment at a temperature of 30° C. for a reaction time of 3.2 h. After the reaction is completed, the mixture is dialyzed and freeze-dried to obtain the functionalized locust bean gum.

[0019] 4. Preparation of wall materials Mix benzoic acid and citric acid, heat to a molten state at a rate of 0.8°C / min, stir evenly, cool at 40°C, and then perform fluidization treatment. The inlet air temperature of the fluidized bed is 30°C, and the outlet air temperature is 25°C. After the fluidization treatment, a wall material is obtained; The mass ratio of the benzoic acid to the citric acid is 1:2.

[0020] 5. Encapsulation The modified core material is added to the wall material, stirred evenly, and then subjected to ultrasonic treatment, the ultrasonic time is 1.2 h, the ultrasonic power is 160 W, and the ultrasonic frequency is 35 kHz. After the ultrasonic treatment, the organic acid-coated tryptophan granular feed is obtained by granulation and drying; The mass ratio of the modified core material to the wall material is 1:2.0.

[0021] Example 2 1. Preparation of Tryptophan Concentrate The fermentation broth was inactivated in an environment of 85°C and pH 5.0 for 5 minutes to obtain a tryptophan concentrate. The solid content of the tryptophan concentrate was controlled to be 40wt%, and the tryptophan content was 20wt% of the total tryptophan concentrate.

[0022] 2. Preparation of core material The tryptophan slurry is dried to obtain crude tryptophan, the crude tryptophan is mixed with 3 times the mass of deionized water, stirred evenly, and then shot blasted to obtain micro-pellets, the micro-pellets are sieved to control the micro-pellets to be 10 mm, and then dried at 90° C. for 30 minutes to obtain the core material.

[0023] 3. Preparation of modified core material (1) Composite 12.0 g of core material was placed in 68 g of anhydrous ethanol, and after stirring evenly, 6.4 g of tetraethyl orthosilicate was slowly added, and the addition amount was controlled to be 0.25 g / min. Stirring was performed while adding, and the stirring speed was controlled to be 220 rpm. After the addition was completed, 3.0 g of ammonia solution was added, and the mixture was stirred and reacted at 35°C for 3.7 hours. After the stirring reaction was completed, the mixture was centrifuged at 4200 rpm for 10 minutes to obtain a solid. After washing, the solid was vacuum dried at 54°C for 2.7 hours to obtain a primary modified core material. The mass concentration of the ammonia solution is 22%; (2) Modification 1.8 g of hydroxyethyl cellulose was added to 100 g of isopropanol, and after being stirred evenly, 1.5 g of β-glucan and 19.0 g of primary modified core material were added, the temperature was raised to 40°C, and the mixture was stirred for 1.6 h. Then, 2.3 g of chitosan and 1.4 g of functionalized locust bean gum were added, the temperature was further raised to 60°C, and the mixture was stirred at 260 rpm for 4.8 h. After the stirring was completed, the mixture was dried to obtain a modified core material. The preparation method of the functionalized locust bean gum comprises the following steps: adding 2.2 g of locust bean gum to 100 g of deionized water, and after the gum is completely dissolved, adding 2.7 g of potassium periodate and stirring evenly, reacting the mixture in a light-proof environment at a reaction temperature of 34° C. for a reaction time of 2.8 h. After the reaction is completed, the mixture is dialyzed and freeze-dried to obtain the functionalized locust bean gum.

[0024] 4. Preparation of wall materials Sorbic acid, propionic acid and acetic acid are mixed, heated to a molten state at a rate of 1.2°C / min, stirred evenly, cooled at 60°C, and then fluidized. The inlet air temperature of the fluidized bed is 60°C, and the outlet air temperature is 45°C. After the fluidization treatment, the wall material is obtained; The mass ratio of the sorbic acid, propionic acid and acetic acid is 2:1:1.

[0025] 5. Encapsulation The modified core material is added to the wall material, stirred evenly, and then subjected to ultrasonic treatment, the ultrasonic time is 1.8 hours, the ultrasonic power is 170W, and the ultrasonic frequency is 40kHz. After the ultrasonic treatment, the organic acid-coated tryptophan granular feed is obtained by granulation and drying; The mass ratio of the modified core material to the wall material is 1:4.0.

[0026] Example 3 1. Preparation of Tryptophan Concentrate The fermentation broth was inactivated in an environment of 75°C and pH 4.5 for 15 minutes to obtain a tryptophan concentrate. The solid content of the tryptophan concentrate was controlled to be 35wt%, and the tryptophan content was 15wt% of the total tryptophan concentrate.

[0027] 2. Preparation of core material The tryptophan slurry is dried to obtain crude tryptophan, the crude tryptophan is mixed with 2.5 times the mass of deionized water, stirred evenly, and then shot blasted to obtain micro-pellets, the micro-pellets are sieved to control the micro-pellets to be 5 mm, and then dried at 60° C. for 80 minutes to obtain the core material.

[0028] 3. Preparation of modified core material (1) Composite 10.0 g of core material was placed in 60 g of anhydrous ethanol, and after stirring evenly, 5.8 g of tetraethyl orthosilicate was slowly added, and the addition amount was controlled to be 0.23 g / min. Stirring was performed while adding, and the stirring speed was controlled to be 210 rpm. After the addition was completed, 2.7 g of ammonia solution was added, and the reaction was stirred at 32° C. for 4.0 h. After the stirring reaction was completed, the solid was centrifuged at 4000 rpm for 13 min to obtain a solid. After washing, it was vacuum dried at 52° C. for 3.0 h to obtain a primary modified core material; The mass concentration of the ammonia solution is 20%; (2) Modification 1.6 g of hydroxyethyl cellulose was added to 100 g of isopropanol, and after being stirred evenly, 1.4 g of β-glucan and 18.5 g of primary modified core material were added, and the temperature was raised to 38° C., and the mixture was stirred for 1.5 h. Then, 2.2 g of chitosan and 1.3 g of functionalized locust bean gum were added, and the temperature was further raised to 57° C., and the mixture was stirred at 250 rpm for 5.0 h. After the stirring was completed, the mixture was dried to obtain a modified core material. The preparation method of the functionalized locust bean gum comprises the following steps: adding 2.0 g of locust bean gum to 100 g of deionized water, and after the gum is completely dissolved, adding 2.5 g of potassium periodate and stirring evenly, reacting the mixture in a light-proof environment at a reaction temperature of 32° C. for a reaction time of 3.0 h. After the reaction is completed, the mixture is dialyzed and freeze-dried to obtain the functionalized locust bean gum.

[0029] 4. Preparation of wall materials Formic acid, lactic acid and lauric acid are mixed, heated to a molten state at a rate of 1.0°C / min, stirred evenly, cooled at 50°C, and then fluidized. The inlet air temperature of the fluidized bed is 45°C, and the outlet air temperature is 35°C. After the fluidization treatment, a wall material is obtained; The mass ratio of formic acid, lactic acid and lauric acid is 1:1:1.

[0030] 5. Encapsulation The modified core material is added to the wall material, stirred evenly, and then subjected to ultrasonic treatment, the ultrasonic time is 1.5 h, the ultrasonic power is 165 W, and the ultrasonic frequency is 37 kHz. After the ultrasonic treatment, the organic acid-coated tryptophan granular feed is obtained by granulation and drying; The mass ratio of the modified core material to the wall material is 1:3.0.

[0031] Comparative Example 1 (1) The steps of preparing tryptophan concentrate, preparing core material, and preparing modified core material are exactly the same as those in Example 3; (2) The steps of preparing the wall material and coating are omitted, and the modified core material obtained in the step of preparing the modified core material is the tryptophan granular feed coated with organic acid.

[0032] Comparative Example 2 (1) The steps of preparing tryptophan concentrate and the steps of preparing the core material are exactly the same as those in Example 3; (2) In the step of preparing the modified core material, the modification step is omitted, and the compounding step is exactly the same as that in Example 3; (3) The steps of preparing the wall material and coating are exactly the same as those in Example 3.

[0033] The present invention adopts tryptophan fermentation liquid as the original raw material, and obtains the tryptophan core material through the steps of inactivation, drying and shot blasting; then the tryptophan is modified, firstly silicon dioxide is deposited on the surface of tryptophan to form a uniform silicon dioxide composite layer, so as to achieve the initial coating of the tryptophan core material by silicon dioxide, and then hydroxyethyl cellulose and beta-glucan are added, the hydroxyethyl cellulose has good adhesion, and the beta-glucan can improve the microecological environment of the intestine and promote the absorption of tryptophan, and they are connected by hydrogen bonding, and then functionalized locust bean gum and chitosan are introduced, which form a cross-linked network structure through Schiff base reaction, so as to achieve the composite and further modification of the core material, and finally the surface of the modified core material is coated with organic acid, the carboxyl group of the organic acid can be combined with the hydroxyl group, amino group and the like of the modified core material, so as to improve the binding property of the organic acid layer and the modified core material, so as to make the wall material The invention can be tightly wrapped on the surface of the modified core material, avoiding the phenomenon of the coating layer falling off during storage and transportation; the invention effectively prevents the contact of tryptophan with the external environment by coating the surface of tryptophan with multiple layers, thereby improving the stability of tryptophan, and realizing the slow release of tryptophan, improving the bioavailability of tryptophan, and reducing its loss in the gastrointestinal tract. In the rumen bypass test, most of the tryptophan is not completely degraded in the rumen, which can provide sufficient substrate for small intestine absorption. After entering the small intestine, the tryptophan is continuously and stably released, allowing the small intestine to fully absorb it, meeting the animal's utilization demand for tryptophan, ensuring the normal growth, metabolism and other physiological activities of the animal, and can improve the quality and stability of pellet feed, enhance the palatability of feed, give full play to the functional role of tryptophan, promote the growth and development and immune function of animals, and better meet the nutritional needs of animals.

[0034] Experimental Testing 1. Simulate rumen digestion (1) Test method Using an in vitro simulated digestive tract test, a buffer solution with a pH of 6.6 was prepared to simulate the rumen environment of an animal body; The rumen digestion stability of the organic acid-coated tryptophan pellet feeds prepared in Examples 1-3 and Comparative Examples 1-2 was tested. Specifically, 2.0 g of each of the organic acid-coated tryptophan pellet feeds prepared in Examples 1-3 and Comparative Examples 1-2 was taken and placed at the bottom of a 350 mL stoppered test tube, and then 50 mL of buffer was added. The test tube stopper was tightly closed and placed in a constant temperature shaking incubator. The reaction was carried out at 39° C. at a speed of 100 rpm for 0 h, 2 h, 6 h, 12 h and 24 h, respectively, to obtain a reaction solution 1. 5 mL of the reaction solution 1 was taken out from each test tube, and the tryptophan content in the reaction solution 1 was determined, and the rumen passage rate was calculated. Rumen passing rate % = (unreleased tryptophan content / initial tryptophan content) × 100%; (2) Test results According to the above method, the rumen passage rate of the organic acid-coated tryptophan pellet feed prepared in Examples 1-3 and Comparative Examples 1-2 is as follows:

[0035] 2. Simulated duodenal digestion (1) Test method 1.0 mol / L hydrochloric acid solution was added to the reaction solution 1 in the simulated rumen digestion test, and the pH of the reaction solution 1 was adjusted to 2.4 to simulate the duodenum environment, and the reaction was continued at 100 rpm at 39°C in a constant temperature shaking incubator for 2 h, 6 h, 10 h, 12 h and 24 h, respectively, which were recorded as reaction solution 2; the small intestinal release rate was obtained by measuring the tryptophan content in the reaction solution 2; small intestinal release rate = (tryptophan content in reaction solution 1 - tryptophan content in reaction solution 2) / tryptophan content in reaction solution 1 × 100%; (2) Test results According to the above method, the small intestine release rate of the tryptophan granular feed coated with organic acid obtained in Example 1-3 and Comparative Example 1-2 is as follows:

[0036] In Comparative Examples 1 and 2, Comparative Example 1 omits the steps of preparing the wall material and coating, and Comparative Example 2 omits the modification step in the modified core material, both of which accelerate the release of tryptophan in the feed. In the first 12 hours of the rumen digestion test, too much tryptophan is released and degraded, resulting in a small amount of tryptophan reaching the small intestine, which cannot meet the animal body's nutritional needs for the feed; and in the small intestine digestion test, almost all of the tryptophan is released within the first 10 hours, but the small intestine's absorption capacity is limited, and tryptophan cannot be fully and timely absorbed, thereby reducing the utilization rate of tryptophan and affecting the growth performance of the animal body.

[0037] Unless otherwise specified, all ratios and percentages described in the present invention are by mass ratios and percentages are by mass percentages.

[0038] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing an organic acid-coated tryptophan pellet feed, characterized in that: The method comprises the steps of preparing tryptophan concentrated slurry, preparing core material, preparing modified core material, preparing wall material and coating; The preparation of the modified core material comprises compounding and modifying steps; The modification step comprises: adding hydroxyethyl cellulose to isopropanol, stirring evenly, adding β-glucan and primary modified core material, stirring at 36-40° C. for 1.3-1.6 hours, then adding chitosan and functionalized locust bean gum, heating to 56-60° C., stirring at 240-260 rpm for 4.8-5.2 hours, and obtaining a modified core material; The mass ratio of the hydroxyethyl cellulose, isopropanol, β-glucan, primary modified core material, chitosan and functionalized locust bean gum is 1.4-1.8:100:1.2-1.5:18.0-19.0:2.0-2.3:1.1-1.4; The step of preparing the wall material comprises: melting the organic acid, stirring it evenly, cooling it, and subjecting it to fluidization treatment to obtain the wall material; The organic acid is two or more of formic acid, benzoic acid, lactic acid, citric acid, sorbic acid, lauric acid, propionic acid and acetic acid.

2. The method for preparing an organic acid-coated tryptophan granular feed according to claim 1, characterized in that: The step of preparing the tryptophan concentrated slurry comprises inactivating the wet bacteria in the fermentation broth at 60-85° C. and pH 3.0-5.0 for 5-20 minutes, and then evaporating at 60-110° C. to obtain the tryptophan concentrated slurry, wherein the solid content in the tryptophan concentrated slurry is controlled to be 30-40wt%, and the tryptophan content is 10-20wt% of the total amount of the tryptophan concentrated slurry.

3. The method for preparing an organic acid-coated tryptophan granular feed according to claim 1, characterized in that: The steps of preparing the core material are as follows: drying the tryptophan slurry to obtain crude tryptophan, mixing the crude tryptophan with 2-3 times the mass of deionized water, stirring evenly, and then performing shot blasting to obtain micro-pellets, sieving the micro-pellets to control the micro-pellets to be 1-10 mm, and then drying at 40-90° C. for 30-120 min to obtain the core material.

4. The method for preparing an organic acid-coated tryptophan granular feed according to claim 1, characterized in that: The compounding step is to place the core material in anhydrous ethanol, stir evenly, slowly add tetraethyl orthosilicate, control the addition amount to 0.20-0.25 g / min, stir while adding, control the stirring speed to 200-220 rpm, add ammonia solution after the addition is completed, stir and react at 30-35° C. for 3.7-4.5 hours, after the stirring reaction is completed, centrifuge at 3800-4200 rpm for 10-15 minutes to obtain a solid, wash, and vacuum dry at 50-54° C. for 2.7-3.2 hours to obtain a primary modified core material; The mass ratio of the core material, anhydrous ethanol, tetraethyl orthosilicate and ammonia solution is 8.0-12.0:52-68:5.0-6.4:2.5-3.0; The mass concentration of the ammonia solution is 18-22%.

5. The method for preparing an organic acid-coated tryptophan granular feed according to claim 1, characterized in that: The preparation method of the functionalized locust bean gum comprises the following steps: adding locust bean gum to deionized water, and after the locust bean gum is completely dissolved, adding potassium periodate and stirring evenly, reacting in a light-proof environment at a reaction temperature of 30-34° C. and a reaction time of 2.8-3.2 h. After the reaction is completed, dialyzing and freeze-drying are performed to obtain the functionalized locust bean gum; The mass ratio of the deionized water, locust bean gum and potassium periodate is 100:1.8-2.2:2.3-2.

7.

6. The method for preparing an organic acid-coated tryptophan granular feed according to claim 1, characterized in that: The steps of preparing the wall material are as follows: mixing the organic acid uniformly, heating to a molten state at a rate of 0.8-1.2°C / min, stirring uniformly, cooling at 40-60°C, and then fluidizing. The fluidized bed has an air inlet temperature of 30-60°C and an air outlet temperature of 25-45°C. After the fluidization treatment is completed, the wall material is obtained.

7. The method for preparing an organic acid-coated tryptophan granular feed according to claim 1, characterized in that: The coating step comprises adding the modified core material to the wall material, stirring evenly, and then performing ultrasonic treatment, wherein the ultrasonic treatment time is 1.2-1.8 hours, the ultrasonic power is 160-170 W, and the ultrasonic frequency is 35-40 kHz. After the ultrasonic treatment, granulation and drying are performed to obtain the organic acid-coated tryptophan granular feed; The mass ratio of the modified core material to the wall material is 1:2.0-4.0.

Images