Functional feed additive for improving quality of aquatic products and preparation method thereof

Abstract

The invention belongs to the technical field of aquatic feed and aquatic product quality improvement, and particularly relates to a functional feed additive for improving aquatic product quality and a preparation method of the functional feed additive. The content of volatile basic nitrogen and trimethylamine is reduced, and generation of fishy smell substances is inhibited from the source. Meanwhile, a marine lactobacillus fermentation product is added, and the fermentation product is rich in gamma-aminobutyric acid, inosinic acid and glutamic acid, so that synthesis of flavor amino acid and umami nucleotide in muscles can be induced, and the umami strength and flavor stability of the fish and shrimp meat are improved. According to the invention, a low-temperature compounding and biological fermentation combined process is adopted for preparation, and the process conditions are mild, safe and environment-friendly. The additive can significantly improve the meat quality and sensory quality of fishes and shrimps, is suitable for various aquatic animal feeds, and has a good industrial application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of aquatic feed and quality improvement of aquatic products, and discloses a functional feed additive for improving the quality of aquatic products and a preparation method thereof. BACKGROUND

[0002] With the rapid development of aquaculture, the proportion of fish and shrimp aquatic products in human dietary structure is increasing, and the requirements for their meat flavor and eating quality are also increasing. However, the aquatic products obtained under the existing breeding conditions often have sensory defects such as heavy fishy smell, weak flavor and low content of umami substances, the main reasons of which include the accumulation of volatile basic nitrogen and trimethylamine in aquatic animals, and the low level of flavor amino acids and umami nucleotides in muscle.

[0003] At present, the means for improving the flavor of aquatic products mainly focus on the post-processing stage, such as packaging deodorization, flavor seasoning and preservation treatment, but there are problems of high cost and limited effect. In terms of feed source control, some studies have tried to improve the meat flavor of fish and shrimp by adding Chinese herbal medicine extract, amino acid regulator and fermentation product, but many of them have problems of single action mechanism, unstable functional components or poor processing adaptability, which makes it difficult to achieve the inhibition of fishy smell and the activation of umami from the metabolic pathway in vivo. At the same time, some flavoring agents only play a masking role and cannot fundamentally improve the composition of endogenous flavor substances in muscle. Therefore, it is urgent to develop a functional feed additive with a synergistic regulation mechanism, which can not only inhibit the synthesis and accumulation of fishy smell substances, but also promote the generation of flavor amino acids and umami nucleotides in the muscle of aquatic animals, so as to improve the sensory flavor and quality stability of aquatic products from the source. SUMMARY

[0004] In order to solve the problems mentioned in the background, the purpose of the present application is to provide a functional feed additive for improving the quality of aquatic products and a preparation method thereof, which takes tea polyphenol-chitosan complex and marine source lactic acid bacteria fermentation product as the core, adjusts the ammonia metabolism in aquatic animals and induces the synthesis of umami substances, effectively reduces the content of fishy smell substances, and improves the flavor and sensory quality of fish and shrimp meat.

[0005] The purpose of the present application can be achieved by the following technical solutions:

[0006] A functional feed additive for improving the quality of aquatic products, comprising the following raw materials in parts by weight: tea polyphenol-chitosan complex 10-25 parts, marine source lactic acid bacteria fermentation product 5-15 parts, fish carrier powder 50-70 parts, adhesive 3-8 parts, stabilizer 1-3 parts, phagostimulant 1-5 parts, antioxidant 0.5-3 parts, and slow-release coating agent 1-4 parts.

[0007] Further preferably, the preparation method of the tea polyphenol-chitosan complex comprises the following steps:

[0008] S101. Chitosan powder is added to 1% acetic acid aqueous solution, stirred and dissolved at room temperature to form a clear and uniform chitosan solution, which is de-aerated and ready for use;

[0009] S102. Tea polyphenol solution is added to the solution, and the mass ratio of the two is 1:0.3-1:0.6, and stirred uniformly;

[0010] S103. Glutaraldehyde is added dropwise as a crosslinking agent under stirring, and the reaction is continued for 2-4 hours at 30-40°C;

[0011] S104. Completely freeze under refrigeration, then vacuum dry, take out the freeze-dried sample after the end, use a pulverizer to crush, and sieve to obtain the tea polyphenol-chitosan complex powder.

[0012] Further preferably, the marine source lactic acid bacteria fermentation product is a strain with the ability to produce γ-aminobutyric acid in the genus Lactococcus, which is obtained by fermentation in a liquid medium containing glucose, yeast powder, sodium glutamate and seaweed powder, and the content of γ-aminobutyric acid in the fermentation broth is 100-300 mg / L, the content of inosinic acid is 30-100 mg / L, and the content of glutamic acid is 200-600 mg / L.

[0013] Further preferably, the phagostimulant is selected from yeast hydrolysate, lysine, fish meal hydrolysate or any combination thereof, and the antioxidant is selected from vitamin C, vitamin E, rosemary extract, green tea extract or any combination thereof.

[0014] Further preferably, the slow-release coating agent is selected from one or more of hydroxypropyl methylcellulose, gelatin, gum arabic, and silicon dioxide.

[0015] Further preferably, the carrier powder is soybean meal powder, corn powder, wheat bran or a combination thereof; the binder is starch, sodium alginate or a combination thereof; and the stabilizer is sodium citrate, sodium phytate or a combination thereof.

[0016] A preparation method of a functional feed additive for improving the quality of aquatic products, comprising the following steps:

[0017] S1. Take tea polyphenol-chitosan complex and marine source lactic acid bacteria fermentation product powder for standby;

[0018] S2. Take soybean meal powder, corn powder and wheat bran as carriers, and mix with starch, sodium alginate, sodium citrate, sodium phytate for standby;

[0019] S3. The tea polyphenol-chitosan complex, fermentation product, carrier, binder, stabilizer, yeast hydrolysate, lysine, fish meal hydrolysate, vitamin C, rosemary extract, hydroxypropyl methyl cellulose, gelatin, silicon dioxide are sequentially added into a mixer and stirred evenly;

[0020] S4. The mixture is dried, crushed, and sieved to obtain the functional feed additive for improving the quality of aquatic products.

[0021] Further preferably, the molecular weight of the chitosan used in step S1 is 50000-150000 Da, the mass ratio of tea polyphenol to chitosan is 1:0.3-1:0.6, the crosslinking agent is 0.5%-2% of the mass of chitosan, and the reaction temperature is 30-40℃.

[0022] Further preferably, in step S4, the hot air drying or low-temperature vacuum drying method is used, the drying temperature is 35-45℃, the drying time is 8-12 hours, and the crushing particle size is 80-120 mesh.

[0023] Further preferably, the mass ratio of the tea polyphenol-chitosan complex to the marine source lactic acid bacteria fermentation product is 1:0.2-1:1, and the uniformity of dispersion of the two in the carrier powder is not less than 90%.

[0024] The beneficial effects of the present application are as follows:

[0025] The present application constructs a functional feed additive with tea polyphenol-chitosan complex and marine source lactic acid bacteria fermentation product as the core, realizes the goal of improving the meat quality and flavor of aquatic animals from the source, and has significant beneficial effects. The tea polyphenol-chitosan complex shows good synergistic effect in the intestinal environment. Tea polyphenol has a polyphenol hydroxyl structure and can form a stable complex with volatile amine substances, reducing the accumulation of fishy substances. Chitosan can adsorb free ammonia and small molecule basic metabolites through its cationic properties, regulate the intestinal microecology, and reduce the frequency of amino acid deamination reaction, thereby effectively inhibiting the generation of volatile basic nitrogen and trimethylamine fishy substances. The marine source lactic acid bacteria fermentation product is rich in flavor active ingredients such as gamma-aminobutyric acid, inosinic acid, and glutamic acid, has multiple physiological activities such as inducing feeding, regulating nitrogen metabolism pathways, and promoting intestinal absorption, can significantly increase the content of flavor amino acids and umami nucleotides in fish and shrimp muscle, and improve the taste and flavor characteristics. In addition, the present application adopts a combination of low-temperature compounding, controlled release coating, and optimized mixing process to ensure the stability and functional release efficiency of active components in feed, while ensuring the adaptability of feed processing, the availability of active substances in the intestinal tract of aquatic animals is improved. BRIEF DESCRIPTION OF DRAWINGS

[0026] The present application will be further described below with reference to the accompanying drawings.

[0027] Figure 1 Comparative bar chart of volatile basic nitrogen content in fish body after feeding of example and comparative example samples;

[0028] Figure 2 Comparative bar chart of taste amino acid content in fish body after feeding of example and comparative example samples;

[0029] Figure 3 Comparative bar chart of taste nucleotide content in fish body after feeding of example and comparative example samples. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0031] Embodiment 1

[0032] I. Preparation of tea polyphenol-chitosan complex

[0033] 1.0 g of chitosan was weighed and added to 100 mL of 1.0% (v / v) acetic acid aqueous solution, and stirred at room temperature for 4 hours until completely dissolved. 0.4 g of tea polyphenol powder was weighed and added to 20 mL of deionized water, and ultrasonically dispersed in an ultrasonic cleaner for 15 minutes, and filtered to remove impurities for use. The tea polyphenol solution was slowly added dropwise to the chitosan solution under stirring, and stirring was continued for 1 hour after mixing. Under stirring, 0.5 mL of 0.5% glutaraldehyde aqueous solution was slowly added dropwise to the mixed solution, the reaction temperature was adjusted to 35℃, and stirring was continued for 3 hours. The mixed solution was poured into a freeze-drying dish, pre-cooled at -20℃ for 12 hours, and then transferred to a vacuum freeze-drying machine for freeze-drying for 48 hours to obtain a freeze-dried solid. After crushing, the tea polyphenol-chitosan complex was obtained by 100 mesh screening.

[0034] II. Preparation of functional feed additive

[0035] The functional feed additive comprises the following raw materials in parts by weight: tea polyphenol-chitosan complex 10 parts, marine source lactic acid bacteria fermentation product 5 parts, fish carrier powder 50 parts, adhesive 3 parts, stabilizer 1 part, phagostimulant 1 part, antioxidant 0.5 part, slow-release coating agent 1 part.

[0036] The preparation steps are as follows: 100 g of tea polyphenol-chitosan complex and 50 g of marine source lactic acid bacteria fermentation product powder are weighed, sieved through a 100 mesh sieve, and pre-dried at 35°C for 2 hours, ready for use. 150 g of soybean meal powder, 150 g of corn powder, and 200 g of wheat bran are mixed in a mass ratio of 3:3:4 as a carrier powder. 15 g of starch and 15 g of sodium alginate are dissolved in 80 mL of warm water at 60°C, stirred for 10 minutes, and a binding liquid is prepared. 10 g of stabilizer, 10 g of attractant, 5 g of antioxidant, and 5 g of slow-release coating agent are mixed and continuously stirred for 15 minutes to form a wet material. 2.5 g of gelatin and 2.5 g of hydroxypropyl methyl cellulose are dissolved in 50 mL of hot water, ultrasonically dispersed to form a uniform solution, and sprayed on the surface of the wet material using an air pump spray gun for 5 minutes. After spraying, the mixture is rolled at low speed in a drum-type mixer for 10 minutes. The mixture is thinly spread on a stainless steel tray and sent to a hot air drying oven, set at a temperature of 45°C and dried for 10 hours until the moisture content is ≤10%. After drying, the mixture is pulverized in a high-speed pulverizer for 2 minutes, sieved, and the functional feed additive is obtained.

[0037] Example 2

[0038] The tea polyphenol-chitosan complex is prepared by the same method as in Example 1.

[0039] The functional feed additive is prepared as follows:

[0040] The functional feed additive comprises the following raw materials by weight: tea polyphenol-chitosan complex 25 parts, marine source lactic acid bacteria fermentation product 15 parts, fish carrier powder 70 parts, binding agent 8 parts, stabilizer 3 parts, attractant 5 parts, antioxidant 3 parts, and slow-release coating agent 4 parts.

[0041] The preparation steps are as follows: 250 g of tea polyphenol-chitosan complex and 150 g of marine source lactic acid bacteria fermentation product powder are weighed, sieved, and dried at 35°C for 2 hours, and then prepared. 210 g of soybean meal powder, 210 g of corn powder, and 280 g of wheat bran are mixed as carrier powder. 40 g of starch and 40 g of sodium alginate are dissolved in 200 mL of 60°C warm water, stirred for 10 minutes, and a binding liquid is prepared. 30 g of stabilizer, 50 g of attractant, and 30 g of antioxidant are weighed and prepared. Then 16 g of hydroxypropyl methyl cellulose, 16 g of gelatin, and 8 g of silicon dioxide are weighed, and a sustained-release coating agent is prepared with a mass ratio of 2:2:1, accounting for 40 g in total. All the above components are mixed and continuously stirred for 15 minutes to form a wet material for standby. 5 g of gelatin and 5 g of hydroxypropyl methyl cellulose are dissolved in 50 mL of hot water, ultrasonic dispersed to form a uniform solution, and then sprayed on the surface of the wet material using an air pump spray gun. The spraying lasts for 5 minutes, and then the mixture is rolled at low speed in a drum-type mixer for 10 minutes. The mixture is dried in a hot air drying oven at 45°C for 10 hours until the moisture content is ≤10%. After drying, the mixture is taken out and crushed for 2 minutes with a high-speed crusher, sieved, and the functional feed additive is obtained.

[0042] Example 3

[0043] The preparation method of the tea polyphenol-chitosan complex is the same as that of Example 1.

[0044] The preparation method of the functional feed additive is as follows:

[0045] The functional feed additive comprises the following raw materials by weight: tea polyphenol-chitosan complex 17.5 parts, marine source lactic acid bacteria fermentation product 10 parts, fish carrier powder 60 parts, binding agent 5.5 parts, stabilizer 2 parts, attractant 3 parts, antioxidant 1.75 parts, and sustained-release coating agent 2.5 parts.

[0046] The preparation steps are as follows: 250 g of tea polyphenol-chitosan complex and 150 g of marine source lactic acid bacteria fermentation product powder are weighed, sieved, and dried at 35°C for 2 hours, and then prepared. 210 g of soybean meal powder, 210 g of corn powder, and 280 g of wheat bran are mixed as carrier powder. 40 g of starch and 40 g of sodium alginate are dissolved in 200 mL of 60°C warm water, stirred for 10 minutes, and a binding liquid is prepared. 30 g of stabilizer, 50 g of attractant, and 30 g of antioxidant are weighed and prepared. Then 16 g of hydroxypropyl methyl cellulose, 16 g of gelatin, and 8 g of silicon dioxide are weighed, and a sustained-release coating agent is prepared with a mass ratio of 2:2:1, accounting for 40 g in total. All the above components are mixed and continuously stirred for 15 minutes to form a wet material for standby. 5 g of gelatin and 5 g of hydroxypropyl methyl cellulose are dissolved in 50 mL of hot water, ultrasonic dispersed to form a uniform solution, and then sprayed on the surface of the wet material using an air pump spray gun. The spraying lasts for 5 minutes, and then the mixture is rolled at low speed in a drum-type mixer for 10 minutes. The mixture is dried in a hot air drying oven at 45°C for 10 hours until the moisture content is ≤10%. After drying, the mixture is taken out and crushed for 2 minutes with a high-speed crusher, sieved, and the functional feed additive is obtained.

[0047] Comparative Example 1

[0048] The functional feed additive comprises the following raw materials by weight: 10 parts of marine source lactic acid bacteria fermentation product, 60 parts of carrier powder for fish, 5.5 parts of adhesive, 2 parts of stabilizer, 3 parts of attractant, 1.75 parts of antioxidant, and 2.5 parts of slow-release coating agent.

[0049] The preparation method is as follows: 100 g of marine source lactic acid bacteria fermentation product powder is weighed, sieved and dried, and prepared for use. 180 g of soybean meal powder, 180 g of corn powder and 240 g of wheat bran are mixed as carrier powder. 27.5 g of starch and 27.5 g of sodium alginate are dissolved in 160 mL of warm water at 60°C to prepare an adhesive solution. 20 g of stabilizer, 3017.5 g of antioxidant, and 25 g of slow-release coating agent are weighed. All the above components are mixed and continuously stirred for 15 minutes to form a wet material for standby. 5 g of gelatin and 5 g of hydroxypropyl methylcellulose are dissolved in 50 mL of hot water, and a gas pump spray gun is used to spray on the surface of the wet material. The spraying lasts for 5 minutes, and then the mixture is rolled at low speed in a drum-type mixer for 10 minutes. The mixture is thinly laid on a stainless steel tray and sent into a hot air drying oven, with a temperature setting of 45°C and a drying time of 10 hours, until the moisture content is ≤10%. After drying, the mixture is taken out and pulverized in a high-speed pulverizer for 2 minutes, sieved, and the functional feed additive is obtained.

[0050] Comparative Example 2

[0051] The preparation method of the tea polyphenol-chitosan complex is the same as that of Example 1.

[0052] The preparation method of the functional feed additive is as follows:

[0053] The functional feed additive comprises the following raw materials by weight: 10 parts of marine source lactic acid bacteria fermentation product, 60 parts of carrier powder for fish, 5.5 parts of adhesive, 2 parts of stabilizer, 3 parts of attractant, 1.75 parts of antioxidant, and 2.5 parts of slow-release coating agent.

[0054] The preparation steps are as follows: 175 g of tea polyphenol-chitosan complex and 100 g of conventional Lactococcus lactis fermentation product are weighed and sieved and dried for standby. 180 g of soybean meal powder, 180 g of corn powder and 240 g of wheat bran are mixed as carrier powder. 27.5 g of starch and 27.5 g of sodium alginate are weighed and dissolved in 160 mL of warm water at 60°C to prepare a binding liquid. 20 g of stabilizer, 3017.5 g of antioxidant, 25 g of slow-release coating agent are weighed. All components are mixed and continuously stirred for 15 minutes to form a wet material for standby. 5 g of gelatin and 5 g of hydroxypropyl methylcellulose are dissolved in 50 mL of hot water, and a gas pump spray gun is used to spray on the surface of the wet material. The spraying lasts for 5 minutes, and then the mixture is rolled at low speed in a drum-type mixer for 10 minutes. The mixture is thinly laid on a stainless steel tray and sent into a hot air drying oven, with the temperature set at 45°C and the drying time set at 10 hours, until the moisture content is ≤10%. After drying, the mixture is taken out and pulverized in a high-speed pulverizer for 2 minutes, sieved, and the functional feed additive is obtained.

[0055] Performance detection

[0056] 1. Volatile basic nitrogen content determination

[0057] The fish samples of Examples 1-3 and Comparative Examples 1-2 are fed for 30 days, and then the fish dorsal muscle samples are collected, cut and mixed. 10 g of the sample is accurately weighed, 50 mL of distilled water is added, shaken at 4°C for 30 minutes and then filtered. 10 mL of the filtrate is placed in a Kjeldahl nitrogen determination device, the distilled volatile basic substances are absorbed with 0.01 mol / L boric acid absorption liquid, and titrated with 0.01 mol / L hydrochloric acid standard solution, and the consumption volume is recorded. The volatile basic nitrogen (VBN) value is calculated according to the following formula:

[0058]

[0059] The lower the VBN value, the less the content of amino-type spoilage substances in the sample. The results are shown in Table 1 below.

[0060] Table 1 Volatile basic nitrogen content

[0061] Sample VBN content (mg / 100 g) Example 1 18.6 Example 2 12.3 Example 3 14.8 Comparative Example 1 27.5 Comparative Example 2 23.2

[0062] As can be seen from Table 1, the VBN content of Examples 1-3 is significantly lower than that of Comparative Examples 1 and 2, and the effect of Example 2 is the most significant. It shows that tea polyphenol can combine with amino-type degradation products and free amines to form stable complexes, reduce the generation of volatile basic substances; the chitosan network structure further adsorbs metabolic amines and blocks their diffusion; and the γ-aminobutyric acid and inosinic acid rich in marine source lactic acid bacteria fermentation product can regulate fish amino acid metabolism and deaminase activity, reducing the accumulation of amine precursors from the metabolic pathway. The three synergistically reduce the spoilage amino derivatives in fish meat, and the flavor is more refreshing and stable.

[0063] 2. Trimethylamine content determination

[0064] After 30 days of feeding fish samples with Examples 1-3 and Comparative Examples 1-2, dorsal muscle samples were collected, cut and mixed, 10 g of sample was accurately weighed, 50 mL of trichloroacetic acid solution (7.5%, w / v) was added, and after oscillation extraction at 4°C for 30 minutes, filtration was performed. 5 mL of filtrate was taken, 1 mL of formaldehyde and 5 mL of acetone solution were added, mixed and allowed to react for 10 minutes to form stable adducts of trimethylamine and formaldehyde. After centrifugation (4000 rpm, 10 min), the supernatant was taken, and the absorbance was measured at a wavelength of 410 nm using a spectrophotometer. The trimethylamine content (mg / 100 g) in the sample was calculated according to the standard curve. Each sample was measured 3 times to take the average value. The lower the trimethylamine value, the more effectively the generation of fishy odor precursors is inhibited. The results are shown in Table 2 below.

[0065] Table 2 Trimethylamine content

[0066] Sample Trimethylamine content (mg / 100 g) Example 1 2.35 Example 2 1.42 Example 3 1.76 Comparative Example 1 3.68 Comparative Example 2 3.12

[0067] As can be seen from Table 2, the trimethylamine content of Examples 1-3 is significantly lower than that of Comparative Examples 1 and 2, indicating that the functional feed additive has good effect in inhibiting the generation of fishy odor precursor substances. Among them, the trimethylamine value of Example 2 is the lowest, only 1.42 mg / 100 g, indicating that the synergistic effect is the strongest under the high dose combination. The tea polyphenol-chitosan complex introduced in the present application has good complexing ability, can form stable complexes with trimethylamine through multiple actions such as hydrogen bond and electrostatic interaction, thereby reducing its volatility; at the same time, γ-aminobutyric acid and flavor nucleotide metabolites in the marine source lactic acid bacteria fermentation product can effectively regulate the intestinal microbial structure and amino acid deamination pathway, thereby reducing the generation of trimethylamine from the source. In contrast, Comparative Example 1 does not add a tea polyphenol-chitosan complexing system, and Comparative Example 2 uses a conventional lactic acid bacteria product, both of which result in an increase in trimethylamine levels.

[0068] 3. Flavor improvement and flavor substance determination

[0069] Flavor amino acid content determination: After 30 days of feeding fish samples with Examples 1-3 and Comparative Examples 1-2, fish dorsal muscle tissue was collected, cut and homogenized, 1 g of sample was weighed, 10 mL of 0.02 mol / L hydrochloric acid solution was added, and oscillation extraction was performed at 4°C for 1 hour. Centrifugation was performed at 8000 rpm for 15 min, and the supernatant was filtered through a 0.22 μm filter membrane. Then 1 mL of filtrate was injected into an amino acid automatic analyzer, and the contents of glutamic acid, alanine and glycine were measured, respectively. The concentration was converted by the standard curve, and the result was expressed in mg / 100 g of muscle. Each sample was measured 3 times to take the average value.

[0070] Fresh taste nucleotide content determination: After the fish samples were treated, 1 g of muscle tissue was accurately weighed, added with 10 mL of 5% perchloric acid solution, homogenized and extracted, ultrasonicated in an ice bath for 15 minutes, adjusted to pH 6.5, filtered with a 0.22 μm filter membrane, and 1 mL of the sample was taken and injected into an HPLC system. A C18 chromatographic column was used, the mobile phase was 0.02 mol / L phosphate buffer (pH 6.5) + 5% methanol, the flow rate was 1.0 mL / min, the ultraviolet detection wavelength was 254 nm, the column temperature was 30°C, and the contents of inosinic acid and guanylic acid were determined, and the results were expressed in mg / 100 g of muscle.

[0071] The results are shown in Table 3 below.

[0072] Table 3: Contents of flavor amino acids and fresh taste nucleotides (mg / 100 g)

[0073] Sample Glutamic acid Alanine Glycine Inosinic acid Guanosinic acid Example 1 38.5 21.4 18.2 26.7 5.3 Example 2 45.8 24.6 22.1 35.9 6.8 Example 3 42.1 22.8 20.4 31.2 6.1 Comparative Example 1 28.6 16.2 13.5 17.3 3.7 Comparative Example 2 32.3 18.5 15.7 21.4 4.2

[0074] As can be seen from Table 3, the contents of flavor amino acids such as glutamic acid, alanine and glycine, and the contents of fresh taste nucleotides such as inosinic acid and guanylic acid in Examples 1-3 are significantly higher than those in Comparative Examples 1 and 2, and especially in Example 2, the overall flavor substance content reaches the highest level, showing a significant synergistic enhancement effect. The results show that by introducing the fermentation product of the marine source lactic acid bacteria, the activation of the fresh taste related metabolic pathway in the fish body is effectively promoted, and the fermentation metabolites are rich in γ-aminobutyric acid, inosinic acid and glutamic acid precursors, which can significantly enhance the in vivo glutamic acid decarboxylation, nucleotide synthesis and retention efficiency. At the same time, the tea polyphenol-chitosan complex structure as a carrier sustained-release matrix provides an antioxidant and stable environment, which helps the stable accumulation and flavor performance of the fresh taste substances in the fish body. Comparative Example 1 lacks tea polyphenol-chitosan, and the flavor substance content is significantly low, indicating that the complex structure plays an important role in flavor enhancement; while Comparative Example 2 contains tea polyphenol-chitosan, but due to the use of marine source strains, the flavor induction ability of its metabolites is limited.

[0075] 4. Determination of glutamine synthetase (GS) activity in liver

[0076] After feeding fish samples of Examples 1-3 and Comparative Examples 1-2 for 30 days, liver samples were taken and quickly washed with pre-cooled normal saline, about 0.2 g of liver tissue was weighed, 1.8 mL of pre-cooled lysis buffer (containing 0.05 mol / L Tris-HCl, 0.25 mol / L sucrose, 1 mmol / L EDTA, pH 7.4) was added under the condition of 4°C, and after homogenization treatment, centrifugation was performed at 8000 rpm for 15 minutes, and the supernatant was used for enzyme activity detection. Using a commercial GS activity detection kit, the colorimetric method was used according to the instructions: the rate of change of NADH absorbance at 340 nm was measured, and the enzyme activity unit was calculated. The GS activity is defined as the amount of enzyme required to catalyze the generation of 1 μmol of glutamine per minute, and the unit is U / mg prot (unit protein enzyme activity). The results are shown in Table 4 below.

[0077] Table 4 GS enzyme activity in liver

[0078] Sample GS enzyme activity (U / mg prot) Example 1 12.5 Example 2 16.8 Example 3 14.9 Comparative Example 1 8.1 Comparative Example 2 9.6

[0079] As can be seen from Table 4, the glutamine synthetase activity of the fish liver in Examples 1-3 is significantly higher than that of Comparative Examples 1 and 2, especially Example 2, the enzyme activity reaches 16.8 U / mg prot, showing obvious ammonia metabolism activation effect. The results show that the tea polyphenol-chitosan complex in the present application not only has the physical effect of complexing and adsorbing amino class metabolites, but also can promote the biological transformation process of glutamic acid to glutamine by regulating the nitrogen source signal pathway and the function of the gut-liver axis, thereby accelerating the endogenous detoxification path of ammonia. At the same time, the γ-aminobutyric acid and metabolic precursors rich in marine source lactic acid bacteria fermentation products also play a positive regulatory role in improving ammonia balanced metabolism. Comparative Example 1 lacks tea polyphenol-chitosan structure, and Comparative Example 2 uses conventional lactic acid bacteria, both of which result in low GS activity, further verifying the synergistic advantage of the key combined components in the present application in enhancing ammonia metabolism and improving homeostasis in aquatic animals.

[0080] In the description of the present specification, the description of the terms "one embodiment", "example", "specific example" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0081] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A functional feed additive for improving the quality of aquatic products, characterized in that, It contains the following ingredients by weight: 10-25 parts of tea polyphenol-chitosan complex, 5-15 parts of marine lactic acid bacteria fermentation product, 50-70 parts of fish carrier powder, 3-8 parts of binder, 1-3 parts of stabilizer, 1-5 parts of attractant, 0.5-3 parts of antioxidant, and 1-4 parts of slow-release coating agent.

2. The functional feed additive according to claim 1, characterized in that, The preparation method of the tea polyphenol-chitosan complex includes the following steps: S101. Add chitosan powder to a 1% acetic acid aqueous solution, stir and dissolve at room temperature to form a clear and homogeneous chitosan solution, and let it stand to remove bubbles for later use; S102. Add tea polyphenol solution to the solution, with a mass ratio of 1:0.3 to 1:0.6, and stir until homogeneous; S103. Add glutaraldehyde dropwise as a crosslinking agent under stirring conditions, and continue the reaction at 30-40°C for 2-4 hours; S104. Completely freeze under freezing conditions, then vacuum dry, remove the freeze-dried sample, pulverize it using a pulverizer, and sieve it to obtain the tea polyphenol-chitosan complex powder.

3. The functional feed additive according to claim 1, characterized in that, The marine-derived lactic acid bacteria fermentation product is obtained by fermenting a strain of Lactococcus lactis capable of producing γ-aminobutyric acid in a liquid culture medium containing glucose, yeast powder, monosodium glutamate and seaweed powder. The fermentation broth contains 100-300 mg / L of γ-aminobutyric acid, 30-100 mg / L of inosinic acid, and 200-600 mg / L of glutamic acid.

4. The functional feed additive according to claim 1, characterized in that, The palatability enhancer is selected from yeast hydrolysate, lysine, fish meal hydrolysate, or any combination thereof, and the antioxidant is selected from vitamin C, vitamin E, rosemary extract, green tea extract, or any combination thereof.

5. The functional feed additive according to claim 1, characterized in that, The sustained-release coating agent is selected from one or more of hydroxypropyl methylcellulose, gelatin, gum arabic, and silica.

6. The functional feed additive according to claim 1, characterized in that, The carrier powder is soybean meal powder, corn flour, wheat bran or a combination thereof; the binder is starch, sodium alginate or a combination thereof; and the stabilizer is sodium citrate, sodium phytate or a combination thereof.

7. A method for preparing a functional feed additive to improve the quality of aquatic products, characterized in that, Includes the following steps: S1. Take tea polyphenol-chitosan complex and marine lactic acid bacteria fermentation product powder for later use; S2. Weigh out soybean meal powder, corn flour and wheat bran as carriers, and mix them with starch, sodium alginate, sodium citrate and sodium phytate for later use; S3. Add the tea polyphenol-chitosan complex, fermentation product, carrier, binder, stabilizer, yeast hydrolysate, lysine, fish meal hydrolysate, vitamin C, rosemary extract, hydroxypropyl methylcellulose, gelatin, and silica to the mixer in sequence and stir until homogeneous. S4. Dry, pulverize, and sieve the mixture to obtain the functional feed additive for improving the quality of aquatic products.

8. The method for preparing the functional feed additive according to claim 7, characterized in that, The chitosan used in step S1 has a molecular weight of 50,000 to 150,000 Da, the mass ratio of tea polyphenols to chitosan is 1:0.3 to 1:0.6, the crosslinking agent is 0.5% to 2% of the mass of chitosan, and the reaction temperature is 30 to 40°C.

9. The method for preparing the functional feed additive according to claim 7, characterized in that, In step S4, hot air drying or low-temperature vacuum drying is used, with a drying temperature of 35-45°C, a drying time of 8-12 hours, and a particle size of 80-120 mesh.

10. The functional feed additive according to claim 1, characterized in that, The mass ratio of the tea polyphenol-chitosan complex to the marine lactic acid bacteria fermentation product is 1:0.2 to 1:1, and the dispersion uniformity of the two in the carrier powder is not less than 90%.

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