Tannin microcapsule as well as preparation method and application thereof

Abstract

The invention provides a tannin microcapsule as well as a preparation method and application thereof. The tannin microcapsule comprises a core and a core shell coating the core, the core comprises tannin, and the core shell comprises carboxymethylated chitosan. The tannin coating structure provided by the invention can effectively protect tannin from being affected by oxidation in the storage and use processes, and the stability and nutritional value of the tannin are improved; the chitosan coated on the inner layer can protect tannin from being decomposed in the stomach and is fully decomposed and metabolized in the small intestine, so that the bioavailability of the tannin is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of tannin preparation, and particularly relates to a tannin microcapsule, a preparation method thereof, and an application thereof. Background Art

[0002] Tannin is a natural polyphenolic compound widely present in plants, and has various biological activities, such as antioxidant, antibacterial, anti-inflammatory and other effects, and has potential application value in animal breeding. However, tannin will undergo polycondensation under acidic conditions and strong acid action to produce precipitation, and its digestion and absorption rate in the animal intestine is relatively low, which limits its wide application in animal feed. At the same time, the stimulating effect of tannin on the animal intestine may also affect its normal growth and development. Therefore, how to improve the digestion and absorption rate of tannin in the animal intestine and reduce its adverse effects on the intestine has become an urgent problem to be solved in the current field of animal nutrition. Summary of the Invention

[0003] This solution aims to coat tannin with unique modified carboxymethyl chitosan to overcome the inherent limitations of tannin, broaden its application boundaries, and achieve high-performance applications in multiple fields to meet the needs such as precise drug delivery in biomedicine, long-term food preservation, and efficient protection of materials, thereby filling the relevant technical gaps and providing innovative support for the industrial development.

[0004] In view of this, the present invention provides a tannin microcapsule, characterized in that the tannin microcapsule comprises a core and a core-shell coating the core;

[0005] The core comprises tannin, and the core-shell comprises carboxymethyl chitosan.

[0006] On the basis of the above technical solutions, preferably, the mass ratio of the tannin to the chitosan is (1-5):(50-80).

[0007] On the basis of the above technical solutions, preferably, the degree of substitution of the carboxymethyl chitosan is 0.7-0.8.

[0008] According to another aspect of the present invention, the present invention provides a preparation method of the above-mentioned tannin microcapsule, and the preparation method comprises the following steps:

[0009] Step S1: Mix raw materials containing tannin, glycerol, and mixed oil to obtain core material tannin;

[0010] Step S2: React, wash, and dry a mixture containing chitosan, an ethanol aqueous solution, sodium hydroxide, and sodium chloroacetate to obtain carboxymethyl chitosan;

[0011] Step S3: Stir and dry the solution containing the core material tannin and carboxymethylated chitosan for 2 to obtain carboxymethylated chitosan-coated tannin microcapsule powder.

[0012] Based on the above technical solutions, preferably, the mass ratio of the mixed oil to the chitosan is (20 - 50):(50 - 80).

[0013] Based on the above technical solutions, preferably, in step S2, the mass ratio of the chitosan to the ethanol aqueous solution is 1% - 10%:1.

[0014] Based on the above technical solutions, preferably, the mass ratio of the sodium hydroxide to the ethanol aqueous solution is 2% - 15%:1.

[0015] Based on the above technical solutions, preferably, the mass ratio of the sodium chloroacetate to the ethanol aqueous solution is 2% - 25%:1.

[0016] Based on the above technical solutions, preferably, in step S2, the mass ratio of the chitosan to the ethanol aqueous solution is 2% - 5%:1.

[0017] Based on the above technical solutions, preferably, the mass ratio of the sodium hydroxide to the ethanol aqueous solution is 4% - 10%:1.

[0018] Based on the above technical solutions, preferably, the mass ratio of the sodium chloroacetate to the ethanol aqueous solution is 2% - 10%:1.

[0019] Based on the above technical solutions, preferably, in step S2, the mass ratio of ethanol to water in the ethanol aqueous solution is (50 - 80):(20 - 50).

[0020] Based on the above technical solutions, preferably, in step S2, the reaction temperature is 50 - 70°C and the reaction time is 3 - 6 h.

[0021] Based on the above technical solutions, preferably, the number of washing times is 5 - 10 times.

[0022] Based on the above technical solutions, preferably, the temperature of drying 1 is 50 - 60°C.

[0023] Based on the above technical solutions, preferably, in step S1, the mixed oil is selected from at least one of coconut oil, fish oil, soybean oil, palm oil, and tributyrin.

[0024] Based on the above technical solutions, preferably, in step S3, the stirring time is 30 - 60 min.

[0025] Based on the above technical solutions, preferably, the drying 2 is spray drying.

[0026] Based on the above technical solutions, preferably, the inlet air temperature of the spray drying is 150 - 180 °C, and the outlet air temperature is 80 - 100 °C.

[0027] According to another aspect of the present invention, the present invention provides an application of the tannin microcapsules described above, the tannin microcapsules prepared by the preparation method of the tannin microcapsules described above, in the fields of feed, precise drug delivery in biomedicine, long-term food preservation, and efficient material protection.

[0028] As an alternative embodiment, the present invention prepares tannin microcapsules through the following technical solutions:

[0029] In the present invention, the preparation method of the coating material is as follows:

[0030] (1) Treatment of the core material tannin

[0031] Mix an appropriate amount of tannin with glycerol evenly, and mix the above glycerol with the mixed oil evenly. The above mixed oil includes one or more of coconut oil, fish oil, soybean oil, palm oil, and tributyrin.

[0032] (2) Preparation of the coating layer

[0033] Introduce carboxyl groups (-COOH) into chitosan through a carboxymethylation reaction. Dissolve chitosan in an ethanol aqueous solution, and the ratio of ethanol to water in the ethanol aqueous solution is (50 - 80):(20 - 50). The mass ratio of chitosan added to the ethanol aqueous solution is 1% - 10%, preferably 2% - 5%. After complete dissolution, add sodium hydroxide to fully alkalize chitosan. The mass ratio of sodium hydroxide added to the above aqueous solution is 2% - 15%, preferably 4% - 10%. Add sodium chloroacetate for the carboxylation reaction. The mass ratio of sodium chloroacetate added to the above aqueous solution is 2% - 25%, preferably 2% - 10%. Sodium chloroacetate is slowly added dropwise under stirring to ensure uniform reaction. The reaction temperature is usually 50 - 70 °C, and the reaction time is 3 - 6 h. After the reaction is completed, neutralize the reactants by dropwise adding acetic acid. Subsequently, filter the mixture through a Buchner funnel to separate the solid product and the filtrate. Wash the solid product with an appropriate amount of distilled water multiple times to remove residual salts and unreacted reagents. Filtration is required after each washing. Repeat the washing step more than 5 times and conduct detection to ensure the removal of sodium chloroacetate with slight microbial toxicity. Place the washed solid product in an oven and dry it to a constant weight at 50 - 60 °C to obtain carboxymethylated chitosan.

[0034] The mass ratio of tannin to chitosan is (1-5): (50-80). To use carboxylated chitosan to coat tannin, slowly add the mixed oil to the carboxylated chitosan solution under stirring, and the mass ratio of the added mixed oil to chitosan is (20-50): (50-80). Continue stirring for 30-60 minutes to make the mixed oil uniformly dispersed in the solution. Then use spray drying method to dry, maintain the inlet air temperature at 150-180°C, and the outlet air temperature at 80-100°C. Through the above operation, the tannin microcapsule powder coated with carboxylated chitosan is obtained.

[0035] The present invention aims to provide a highly efficient coating structure for tannin, which can effectively ensure that tannin maintains good performance during storage and various application scenarios, overcome the defects of poor solubility and insufficient stability in animal feed, and accurately adapt to the needs of different fields to achieve the release of targeted functions.

[0036] To achieve the above-mentioned purpose, the present invention uses tannin as the main component and dissolves the tannin in the mixed oil. The outer coating layer uses chitosan with carboxyl (-COOH) groups that are sensitive to pH. (Carboxyl groups usually exist in a non-ionized form in an acidic environment, which makes the chitosan structure relatively stable. Under the acidic conditions of the stomach, carboxyl groups are not easy to react and can effectively protect tannin. Carboxymethyl-modified chitosan introduces carboxymethyl groups, which makes the molecular chain carry more negative charges. Compared with unmodified chitosan, its charge distribution changes significantly. This change affects the electrostatic interaction between molecules. In an aqueous environment, negative charges repel each other, the degree of stretching of the molecular chain increases, and the originally tightly aggregated chitosan structure becomes relatively loose. The loose structure provides more contact sites for degradation media (such as enzymes, chemical reagents, etc.). At the same time, the introduction of carboxyl groups changes the crystallinity of chitosan. Unmodified chitosan has certain crystalline areas, which are regular and tight, hindering the penetration of degradation media. Carboxymethyl-modified chitosan weakens its crystallinity, making the entire molecular structure more disordered, allowing degradation media to enter smoothly, "disintegrate" the molecular chain from the inside, and accelerate the degradation rate. When entering the alkaline environment of the small intestine, the carboxyl group is ionized, changing the charge distribution and structure of chitosan, promoting the degradation of chitosan, and releasing tannins for metabolism. It can be effectively placed in the strong acidity of the stomach to prevent tannins from precipitating in the stomach. When it reaches the alkaline environment of the small intestine, the modified chitosan can respond to the changes and accurately release tannins to exert its efficacy, which is expected to break through the application bottleneck and expand applications in multiple fields.

[0037] The modified coated tannin provided by the present invention has more application fields and better performance; supplementing short / medium / long-chain fatty acids has a very significant effect in feed. On the one hand, the feed containing tannin microcapsules can improve the growth performance of animals, optimize nutrient absorption, enhance energy utilization, and help them grow rapidly; on the other hand, it can improve the health of animals, maintain their physiological functions, and prevent nutritional deficiency diseases; and further stabilize the physical properties of the feed and ensure the quality stability of the feed.

[0038] The present invention coats tannin with a unique modified carboxymethyl chitosan, overcomes the inherent limitations of tannin, broadens its application boundaries, and realizes high-performance applications in multiple fields to meet the needs such as precise drug delivery in biomedicine, long-term preservation of food, and efficient protection of materials, thereby filling the relevant technical gaps and providing innovative support for industrial development.

[0039] The feed containing tannin microcapsules of the present invention has the following beneficial effects compared with the prior art:

[0040] (1) Adding tannin microcapsules to the feed containing tannin microcapsules provided by the present invention, the tannin coating structure can effectively protect tannin from oxidation during storage and use, improving its stability and nutritional value.

[0041] (2) Adding tannin microcapsules to the feed containing tannin microcapsules provided by the present invention, the chitosan coated on the inner layer can protect tannin from being decomposed in the stomach and be fully decomposed and metabolized in the small intestine, improving the bioavailability of tannin.

[0042] (3) For the feed containing tannin microcapsules provided by the present invention, the feed with balanced fatty acids can ensure that animals absorb the nutrients in it more efficiently, enhance the energy utilization of the feed; thereby further improving the health status of animals. Specific embodiments

[0043] The following will describe clearly and completely the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0044] Example 1 Preparation of tannin microcapsules

[0045] (1) Treatment of core material tannin

[0046] Mix 1 g of tannin evenly with 20 g of glycerol, and evenly mix the above glycerol with 20 g of soybean oil mixed oil.

[0047] (2) Preparation of coating layer

[0048] Dissolve 50 g of chitosan in 5000 g of an ethanol aqueous solution with the ratio of ethanol to water being 50:20. The mass ratio of chitosan added to the ethanol aqueous solution is 1%. After complete dissolution, add 100 g of sodium hydroxide to fully alkalize the chitosan, and the mass ratio of sodium hydroxide added to the above aqueous solution is 2%. Add 100 g of sodium chloroacetate for carboxylation reaction, and the mass ratio of sodium chloroacetate added to the above aqueous solution is 2%. Sodium chloroacetate is slowly added dropwise under stirring to ensure uniform reaction. The reaction temperature is 70 °C and the reaction time is 3 h. After the reaction is completed, neutralize the reactants by dropwise adding acetic acid. Subsequently, filter the mixture through a Buchner funnel to separate the solid product and the filtrate. Wash the solid product with an appropriate amount of distilled water multiple times to remove residual salts and unreacted reagents. Filter after each washing, repeat the washing step 5 times, and conduct detection to ensure the removal of sodium chloroacetate with slight microbial toxicity. Place the washed solid product in an oven and dry it to a constant weight at 50 °C to obtain carboxymethyl chitosan with a degree of substitution of 0.7.

[0049] Under stirring, slowly add 20 g of soybean oil mixed oil to the carboxymethyl chitosan solution. The mass ratio of the added mixed oil to chitosan is 20:50. Continue stirring for 30 min to uniformly disperse the mixed oil in the solution. Subsequently, use spray drying for drying, with the inlet air temperature maintained at 150 °C and the outlet air temperature at 80 °C; obtain tannin microcapsule powder coated with carboxymethyl chitosan.

[0050] Preparation of tannin microcapsules in Example 2

[0051] (1) Treatment of core material tannin

[0052] Uniformly mix 3 g of tannin with 20 g of glycerol, and uniformly mix the above glycerol with 30 g of soybean oil mixed oil.

[0053] (2) Preparation of coating layer

[0054] Dissolve 60 g of chitosan in 1200 g of an ethanol aqueous solution, where the ratio of ethanol to water in the ethanol aqueous solution is 60:40, and the mass ratio of chitosan added to the ethanol aqueous solution is 5%. After complete dissolution, add 120 g of sodium hydroxide to fully alkalize the chitosan, and the mass ratio of sodium hydroxide added to the above aqueous solution is 10%. Add 120 g of sodium chloroacetate for carboxylation reaction, and the mass ratio of sodium chloroacetate added to the above aqueous solution is 10%. Sodium chloroacetate is slowly added dropwise under stirring to ensure uniform reaction progress. The reaction temperature is usually 60 °C, and the reaction time is 4 h. After the reaction is completed, neutralize the reactants by dropwise adding acetic acid. Subsequently, filter the mixture through a Buchner funnel to separate the solid product and the filtrate. Wash the solid product with an appropriate amount of distilled water multiple times to remove residual salts and unreacted reagents. Filtration is required after each washing, and the washing step is repeated 7 times to ensure the removal of sodium chloroacetate with slight microbial toxicity. Place the washed solid product in an oven and dry it to a constant weight at 55 °C to obtain carboxymethylated chitosan, and the degree of substitution of carboxymethylated chitosan is 0.75.

[0055] Under stirring, slowly add 30 g of soybean oil mixed oil to the carboxymethylated chitosan solution, and the mass ratio of the added mixed oil amount to chitosan is 30:60. Continue stirring for 40 min to evenly disperse the mixed oil in the solution. Subsequently, use spray drying for drying, with the inlet air temperature maintained at 160 °C and the outlet air temperature at 90 °C; obtain tannin microcapsule powder coated with carboxymethylated chitosan.

[0056] Example 3 Preparation of Tannin Microcapsules

[0057] (1) Treatment of Core Material Tannin

[0058] Uniformly mix 5 g of tannin with 20 g of glycerol, and uniformly mix the above glycerol with 50 g of soybean oil mixed oil.

[0059] (2) Preparation of Coating Layer

[0060] Dissolve 80 g of chitosan in 800 g of an ethanol aqueous solution with the ratio of ethanol to water being 80:50. The mass ratio of chitosan added to the ethanol aqueous solution is 10%. After complete dissolution, add 120 g of sodium hydroxide to fully alkalize the chitosan, and the mass ratio of sodium hydroxide added to the above aqueous solution is 15%. Add 200 g of sodium chloroacetate for carboxylation reaction, and the mass ratio of sodium chloroacetate added to the above aqueous solution is 25%. Sodium chloroacetate is slowly added dropwise under stirring to ensure uniform reaction. The reaction temperature is usually 50 °C, and the reaction time is 6 h. After the reaction is completed, the reactants are neutralized by dropwise adding acetic acid. Subsequently, the mixture is suction filtered through a Buchner funnel to separate the solid product and the filtrate. The solid product is washed multiple times with an appropriate amount of distilled water to remove residual salts and unreacted reagents. Filtration is required after each washing, and the washing step is repeated 10 times. Detection is carried out to ensure the removal of sodium chloroacetate with slight microbial toxicity. The washed solid product is placed in an oven and dried to a constant weight at 60 °C to obtain carboxymethylated chitosan, and the degree of substitution of carboxymethylated chitosan is 0.8.

[0061] Under stirring conditions, slowly add 50 g of soybean oil mixed oil to the carboxylated chitosan solution. The mass ratio of the added mixed oil amount to chitosan is 50:80. Continue stirring for 60 min to uniformly disperse the mixed oil in the solution. Subsequently, spray drying is used for drying, with the inlet air temperature maintained at 180 °C and the outlet air temperature at 100 °C to obtain tannin microcapsule powder coated with carboxylated chitosan.

[0062] Example 4

[0063] This example provides a laying hen feed, including a basic chicken feed and the tannin microcapsule powder prepared in Example 1. Among them, the weight percentage of the tannin microcapsule powder in the feed is 1.0%. Among them, the basic chicken feed is composed of the following raw materials by weight percentage: 20% corn, 15% fermented fungus bran, 1% fermented soybean meal, 10% fermented soybean residue, 1% stone powder, 1% fish meal, 1% calcium gluconate powder, 0.1% iron methionine, and 0.1% vitamin premix. The test animal facilities continuously maintain the ordinary environmental standards, with the environmental temperature being 20 - 28 °C, the relative humidity range being 40% - 70%, artificial lighting, and a 12-hour light-dark cycle. The feeding conditions are carried out according to the "Technical Regulations for Laying Hen Feeding Trials for Safety Evaluation of Livestock and Poultry Feeds (GB / T 40837 - 2021)".

[0064] Randomly select more than 160,000 36-week-old laying period Dawu Jinfeng laying hens for the test, and randomly divide them into two groups, with each group having half of the number in the control group and the test group. Among them, the control group is fed with the basic laying hen diet, and the test group's diet is additionally added with tannin microcapsule powder (1.0%). The test period is 26 days, and then the laying rate, feed-to-meat ratio, and death and culling rate of the laying hens are compared. The test results are represented by the average values of each group, as shown in Table 1.

[0065] Comparative Example 1

[0066] This comparative example provides a laying hen feed, including basic chicken feed and soybean oil (1%). Wherein, the basic chicken feed is composed of the following raw materials in weight percentage: 20% corn, 15% fermented fungus bran, 1% fermented soybean meal, 10% fermented bean dregs, 1% stone powder, 1% fish meal, 1% calcium fruit acid powder, 0.1% methionine iron, and 0.1% vitamin premix. The experimental animal facilities continue to maintain normal environmental standards, with an ambient temperature of 20-28°C, a relative humidity range of 40% to 70%, artificial lighting, and alternating light and dark every 12 hours. The feeding conditions are managed in accordance with the "GB / T40837-2021 Technical Regulations for Laying Hens Feeding Tests for Safety Evaluation of Livestock and Poultry Feeds".

[0067] The experiment randomly selected more than 160,000 Dawu Jinfeng laying hens in the egg-laying period of 36 weeks old and randomly divided them into two groups, with half the number of control groups and half the number of experimental groups; the control group was fed with a basic diet for laying hens, while the experimental group was fed with an additional soybean oil (1.0%). The experimental period was 26 days, and then the egg production rate, feed-to-meat ratio, and mortality rate of the laying hens were compared. The experimental results were expressed as the average values ​​of each group, as shown in Table 1.

[0068] Example 5

[0069] This embodiment provides a laying hen feed, including a basic chicken feed and the tannin microcapsule powder prepared in Example 1, wherein the weight percentage of the tannin microcapsule powder in the feed is 0.5%. The basic chicken feed is composed of the following raw materials by weight: 20% corn, 15% fermented fungus bran, 1% fermented soybean meal, 10% fermented bean dregs, 1% stone powder, 1% fish meal, 1% calcium fruit acid powder, 0.1% methionine iron, and 0.1% vitamin premix. The experimental animal facility continues to maintain ordinary environmental standards, with an ambient temperature of 20-28°C, a relative humidity range of 40% to 70%, artificial lighting, and alternating light and dark every 12 hours. The feeding conditions are managed in accordance with the "GB / T40837-2021 Technical Regulations for Laying Hens Feeding Test for Safety Evaluation of Livestock and Poultry Feed".

[0070] The experiment randomly selected more than 160,000 Dawu Jinfeng laying hens in the egg-laying period of 36 weeks old and randomly divided them into two groups, with half the number of control groups and half the number of experimental groups; the control group was fed with a basic diet for laying hens, while the experimental group was fed with an additional tannic acid microcapsule powder (0.5%). The experimental period was 26 days, and then the egg production rate, feed-to-meat ratio, and mortality rate of laying hens were compared. The experimental results were expressed as the average values ​​of each group, as shown in Table 1.

[0071] Comparative Example 2

[0072] This comparative example provides a layer feed, including a basic chicken feed and tannin microcapsule powder (the microcapsule core-shell is unmodified chitosan). Among them, the weight percentage of the tannin microcapsule powder in the feed is 1.0%, and the wall material of the microcapsule is unmodified chitosan. Among them, the basic chicken feed is composed of the following raw materials in weight percentages: corn 20%, fermented fungus bran 15%, fermented soybean meal 1%, fermented soybean residue 10%, stone powder 1%, fish meal 1%, calcium acid fruit powder 1%, iron methionine 0.1%, vitamin premix 0.1%. The experimental animal facilities continuously maintain the ordinary environmental standards, the environmental temperature is 20 - 28 °C, the relative humidity range is 40% - 70%, with artificial lighting, and the light and dark alternate every 12 hours. The feeding conditions are carried out according to the "Technical Regulations for Laying Hen Feeding Tests on Safety Evaluation of Livestock and Poultry Feeds (GB / T 40837 - 2021)".

[0073] Randomly select more than 160,000 36-week-old laying period Dawu Jinfeng laying hens for the experiment, and randomly divide them into two groups, with an equal number in the control group and the experimental group; among them, the control group is fed with the basic laying hen diet, and the experimental group's diet is additionally supplemented with tannic acid microcapsule powder (the microcapsule core-shell is unmodified chitosan) (1.0%). The experimental period is 26 days, and then the laying rate, feed-to-meat ratio, and mortality rate of the laying hens are compared. The experimental results are expressed as the average values of each group, as shown in Table 1.

[0074] Example 6

[0075] This example provides a layer feed, including a basic chicken feed and the tannin microcapsule powder prepared in Example 1. Among them, the weight percentage of the tannin microcapsule powder in the feed is 0.8%. Among them, the basic chicken feed is composed of the following raw materials in weight percentages: corn 20%, fermented fungus bran 15%, fermented soybean meal 1%, fermented soybean residue 10%, stone powder 1%, fish meal 1%, calcium acid fruit powder 1%, iron methionine 0.1%, vitamin premix 0.1%. The experimental animal facilities continuously maintain the ordinary environmental standards, the environmental temperature is 20 - 28 °C, the relative humidity range is 40% - 70%, with artificial lighting, and the light and dark alternate every 12 hours. The feeding conditions are carried out according to the "Technical Regulations for Laying Hen Feeding Tests on Safety Evaluation of Livestock and Poultry Feeds (GB / T 40837 - 2021)".

[0076] Randomly select more than 160,000 36-week-old laying period Dawu Jinfeng laying hens for the experiment, and randomly divide them into two groups, with an equal number in the control group and the experimental group; among them, the control group is fed with the basic laying hen diet, and the experimental group's diet is additionally supplemented with tannic acid microcapsule powder (0.8%). The experimental period is 26 days, and then the laying rate, feed-to-meat ratio, and mortality rate of the laying hens are compared. The experimental results are expressed as the average values of each group, as shown in Table 1.

[0077] Comparative Example 3

[0078] In step (1) of Example 1, replace the dosage of tannin with 0.5 g, and keep the remaining preparation steps the same as those in Example 1.

[0079] Randomly select more than 160,000 36-week-old laying Dawa Jinfeng laying hens during the laying period, and randomly divide them into two groups with equal numbers in the control group and the experimental group; among them, the control group is fed with the basic diet for laying hens, and the experimental group is additionally fed with the tannin microcapsule powder (1.0%) in Comparative Example 3 in the diet. The test period is 26 days, and then the laying rate, feed-to-meat ratio, and mortality rate of the laying hens are compared. The test results are expressed as the average value of each group, as shown in Table 1.

[0080] Comparative Example 4

[0081] In step (1) of Example 1, replace the dosage of tannin with 6 g, and keep the remaining preparation steps the same as those in Example 1.

[0082] Randomly select more than 160,000 36-week-old laying Dawa Jinfeng laying hens during the laying period, and randomly divide them into two groups with equal numbers in the control group and the experimental group; among them, the control group is fed with the basic diet for laying hens, and the experimental group is additionally fed with the tannin microcapsule powder (1.0%) in Comparative Example 4 in the diet. The test period is 26 days, and then the laying rate, feed-to-meat ratio, and mortality rate of the laying hens are compared. The test results are expressed as the average value of each group, as shown in Table 1.

[0083] Comparative Example 5

[0084] In step (2) of Example 1, replace the dosage of sodium chloroacetate with 1%, that is, add 50 g of sodium chloroacetate for carboxylation reaction, and the degree of substitution of carboxymethyl chitosan is 0.65. Keep the remaining preparation steps the same as those in Example 1.

[0085] Randomly select more than 160,000 36-week-old laying Dawa Jinfeng laying hens during the laying period, and randomly divide them into two groups with equal numbers in the control group and the experimental group; among them, the control group is fed with the basic diet for laying hens, and the experimental group is additionally fed with the tannin microcapsule powder (1.0%) in Comparative Example 4 in the diet. The test period is 26 days, and then the laying rate, feed-to-meat ratio, and mortality rate of the laying hens are compared. The test results are expressed as the average value of each group, as shown in Table 1.

[0086] Comparative Example 6

[0087] In step (2) of Example 1, replace the dosage of sodium chloroacetate with 26%, that is, add 1300 g of sodium chloroacetate for carboxylation reaction, and the degree of substitution of carboxymethyl chitosan is 0.85. Keep the remaining preparation steps the same as those in Example 1.

[0088] More than 160,000 Dawa Jinfeng laying hens at 36 weeks of laying age were randomly selected and divided into two groups with equal numbers in the control group and the experimental group. Among them, the control group was fed with the basic diet for laying hens, and the experimental group was additionally fed with the tannin microcapsule powder (1.0%) in Comparative Example 4. The test period was 26 days, and then the laying rate, feed-to-meat ratio, and death and culling rate of the laying hens were compared. The test results were expressed as the average value of each group, as shown in Table 1.

[0089] Table 1 Detection results of laying hen production performance

[0090]

[0091] As shown in Table 1, the laying hens in the control group were the same as those in the control group of Example 4. The corresponding data in Examples 4-6 were for the laying hens in the experimental groups of Examples 4-6, and the corresponding data in Comparative Examples 1-6 were for the laying hens in the experimental groups of Comparative Examples 1-6. In Comparative Example 1, no tannin microcapsule powder was added, and the laying rate of the laying hens was lower than that of the laying hens in Examples 4-6, and the death and culling rate of the laying hens was higher than that of the laying hens in Examples 4-6. In Comparative Example 2, the chitosan in the added tannin microcapsule powder was not chitosan-modified, and the laying rate of the laying hens was lower than that of the laying hens in the control group and Examples 4-6, and the death and culling rate was higher than that of the laying hens in the control group and Examples 4-6. In Comparative Example 3, the dosage of tannin in the added tannin microcapsule powder was less than the range of the mass ratio of tannin to chitosan (1-5):(50-80). In Comparative Example 4, the dosage of added tannin was less than the range of the mass ratio of tannin to chitosan (1-5):(50-80). In Comparative Example 5, the degree of substitution of carboxymethyl chitosan in the added tannin microcapsule powder was less than 0.7. In Comparative Example 5, the degree of substitution of carboxymethyl chitosan in the added tannin microcapsule powder was greater than 0.8. To sum up, the feed containing tannin microcapsules can, on the one hand, improve the growth performance of animals, optimize nutrient absorption, enhance energy utilization, and help them grow rapidly; on the other hand, it can improve the health of animals, maintain their physiological functions, and prevent nutritional deficiency diseases; and further stabilize the physical properties of the feed and ensure the quality stability of the feed.

[0092] Test example Shelf life test of coating

[0093] I. Preparation of storage test samples:

[0094] Using the specific preparation steps in Example 1, multiple groups of tannin microcapsule powder samples were prepared, and the weight of each group of samples was 50-100 g. At the same time, uncoated tannin samples were prepared as controls.

[0095] The samples were separately placed in sealed brown glass bottles to prevent the influence of light on the samples.

[0096] Storage condition settings: Different temperature and humidity conditions were set, namely high temperature and high humidity (temperature 35°C, relative humidity 75%), normal temperature and normal humidity (temperature 25°C, relative humidity 50%), and low temperature and low humidity (temperature 4°C, relative humidity 30%). The same number of sample groups were placed under each condition and stored for 1 month, 3 months, 6 months, and 12 months respectively.

[0097] Detection indicators and methods: Samples were taken out regularly (every month) to detect the tannin content, oxidation index (peroxide value), and the structural integrity of the microcapsules.

[0098] The tannin content was determined by the spectrophotometric method for the determination of tannin in feeds GB / T 27985-2011.

[0099] The peroxide value was detected according to the national food safety standard Determination of peroxide value in foods GB 5009.227-2023.

[0100] II. Storage test data

[0101] Change in tannin content: After 12 months of storage under normal temperature and normal humidity conditions, the retention rate of tannin content in the coated tannin microcapsules reached 80-90%, while the tannin content in the uncoated tannin samples only retained 30-50% within the same time.

[0102] Under high temperature and high humidity conditions, the retention rate of tannin content in the coated tannin microcapsules was 90-95% at 6 months, and the tannin content of the uncoated tannin samples had dropped significantly to 60% at 3 months.

[0103] Oxidation index: After 12 months of storage, the peroxide value of the coated tannin microcapsules under normal temperature and normal humidity conditions was 5.8 mg / kg. In contrast, the peroxide value of the uncoated tannin samples reached 32.2 mg / kg. Under high temperature and high humidity conditions, the difference was even more significant.

[0104] Structural integrity of microcapsules: It was found through observation that under different storage conditions, the structure of the coated tannin microcapsules remained basically intact within 12 months, with only a small number of microcapsules showing slight deformation or fine surface cracks, and the coating rate reached 85-95%. While obvious agglomeration and caking occurred during the storage of uncoated tannin.

[0105] III. In vitro digestion - small intestine digestibility test

[0106] Preparation of simulated gastrointestinal environment:

[0107] Simulated gastric juice: Simulated gastric juice with a pH of 1.2 - 2.0 was prepared or purchased, which contained components such as pepsin to simulate the digestive environment in the stomach.

[0108] Simulated intestinal fluid: Prepare or purchase simulated intestinal fluid with a pH of 7.0 - 8.0, containing components such as trypsin and bile salts, to simulate the digestive environment of the small intestine.

[0109] Experimental procedure:

[0110] Take the tannin microcapsule powder sample prepared in Example 1 (accurate to 100 mg), place it in simulated gastric fluid, and oscillate it in a constant temperature oscillator at 37°C at a speed of 50 - 150 r / min for 3 - 4 hours to simulate the gastric digestion process.

[0111] Then transfer the sample in the gastric fluid to the simulated intestinal fluid and continue to oscillate at 37°C. Take out 5 ml of the sample solution at 1 hour, 2 hours, 4 hours, 6 hours, and 8 hours respectively; determine it by the spectrophotometric method for the determination of tannin in feeds in GB / T 27985 - 2011; determine the tannin content released into the intestinal fluid at different time points.

[0112] Control group setting:

[0113] Use the purchased tannin directly for the experiment and set it as the control group of uncoated tannin. Conduct the above - mentioned simulated gastrointestinal digestion experiment in the same way to compare the release differences of coated and uncoated tannin in the gastrointestinal environment.

[0114] Loss rate X = (a - b) / a * 100%; a and b are the effective contents of tannin before and after the test.

[0115] After calculation, the loss rate of uncoated tannin is 30 - 40%, and the loss rate of coated tannin is within 5%.

[0116] IV. Small intestine release test data

[0117] According to the tannin release amounts measured at different time points, record the relevant data of the tannin microcapsules prepared in Examples 1 - 3 in the small intestine. The results show that in the simulated small intestine environment, the tannin microcapsules start to slowly release tannin at 2 - 4 hours, the release rate gradually increases at 4 - 6 hours, and the release amount reaches 80% at 6 hours. The specific experimental results are shown in Table 2 below.

[0118] The release data of the modified tannin microcapsules prepared in Examples 1 - 3 are: 2 - 4 h, the release rate is 20 - 30%, 4 - 6 h the release rate is 30 - 50%. After 6 h, the cumulative release reaches 80%. The specific experimental results are shown in Table 2 below.

[0119] Conduct a small intestine simulation experiment with the directly purchased tannin. The release data of the uncoated tannin are: 2 - 4 h, the release rate is 30 - 40%, 4 - 6 h the release rate is 60%, and after 6 h, the cumulative release reaches 70 - 75%. The specific experimental results are shown in Table 2 below.

[0120] Table 2 Small intestine release table of coated tannin microcapsules and uncoated tannin.

[0121]

[0122] Compared with the control group:

[0123] When directly using tannin, the uncoated tannin is released in large quantities within a short period (1 - 2 hours) after entering the simulated intestinal fluid, and the release amount reaches 70% within 2 hours. Subsequently, the release rate gradually slows down, but it is basically completely released within 6 hours. In contrast, the coated tannin microcapsules prepared in Examples 1 - 3 can achieve slow and continuous release, and the release rate reaches 80% within 8 hours, effectively avoiding the too-fast release of tannin in the front section of the small intestine and improving its absorption and utilization rate in the small intestine.

[0124] In summary, the tannin coating structure of the present invention can effectively protect tannin from oxidation during storage and use, and at the same time can protect tannin from being decomposed in the stomach and be fully decomposed and metabolized in the small intestine, improving the bioavailability of tannin. This structure has the advantages of simple preparation method and remarkable effect, and is suitable for large-scale production and application.

Claims

1. A tannin microcapsule, characterized in that: The tannin microcapsule comprises a core and a core shell covering the core; The core comprises tannin, and the core shell comprises carboxymethylated chitosan.

2. The tannin microcapsule according to claim 1, characterized in that: The mass ratio of the tannin to the chitosan is (1-5):(50-80).

3. The tannin microcapsule according to claim 1, characterized in that: The substitution degree of the carboxymethylated chitosan is 0.7-0.

8.

4. The method for preparing tannin microcapsules according to claim 1, characterized in that: The preparation method comprises the following steps: Step S1: mixing raw materials containing tannin, glycerin and mixed oil to obtain core material tannin; Step S2: reacting, washing and drying a mixture containing chitosan, ethanol aqueous solution, sodium hydroxide and sodium chloroacetate to obtain carboxymethylated chitosan; Step S3: Stir and dry the solution containing the core material tannin and carboxymethylated chitosan 2 to obtain tannin microcapsule powder coated with carboxymethylated chitosan.

5. The preparation method according to claim 4, characterized in that: The mass ratio of the mixed oil to the chitosan is (20-50):(50-80).

6. The preparation method according to claim 4, characterized in that: In the step S2, the mass ratio of the chitosan to the ethanol aqueous solution is 1% to 10%:1; The mass ratio of the sodium hydroxide to the ethanol aqueous solution is 2% to 15%:1; The mass ratio of the sodium chloroacetate to the ethanol aqueous solution is 2% to 25%:

1.

7. The preparation method according to claim 6, characterized in that: In the step S2, the mass ratio of the chitosan to the ethanol aqueous solution is 2% to 5%:1; The mass ratio of the sodium hydroxide to the ethanol aqueous solution is 4% to 10%:1; The mass ratio of the sodium chloroacetate to the ethanol aqueous solution is 2% to 10%:

1.

8. The preparation method according to claim 4, characterized in that: In the step S2, the mass ratio of ethanol to water in the ethanol aqueous solution is (50-80): (20-50); In step S2, the reaction temperature is 50-70° C. and the reaction time is 3-6 hours; The number of washings is 5 to 10 times; The temperature of the drying 1 is 50-60°C.

9. The preparation method according to claim 4, characterized in that: In step S1, the mixed oil is selected from at least one of coconut oil, fish oil, soybean oil, palm oil, and tributyrin; In step S3, the stirring time is 30 to 60 minutes; The drying 2 is spray drying; The inlet air temperature of the spray drying is 150-180°C, and the outlet air temperature is 80-100°C.

10. Application of the tannin microcapsules prepared by the tannin microcapsules as claimed in any one of claims 1 to 3 or the method for preparing the tannin microcapsules as claimed in any one of claims 4 to 9 in the fields of feed, precise drug release of biomedicine, long-term preservation of food, and efficient protection of materials.

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