Slow-sinking fish feed and preparation method thereof

Abstract

The invention provides a slow-sinking fish feed and a preparation method thereof, wherein the slow-sinking fish feed comprises the following raw materials in parts by weight: 30-40 parts of fish meal, 20-30 parts of soybean meal, 10-20 parts of corn flour, 4-6 parts of vegetable oil, 2-4 parts of biofilm composite agent, 1-3 parts of starch nanocrystal, 0.5-1.5 parts of antibacterial agent, 0.6-1.2 parts of premix, wherein the biofilm composite agent is composed of sunflower wax, lignin, and sodium alginate in a mass ratio of (1.0-2.0): (1.0-1.5): (0.8-1.6). The crystalline structure and nanometer size of starch nanocrystal enable it to penetrate into the internal structure of the feed and be closely combined with other components in the feed. This combination increases the structural stability and hardness of the feed, allowing it to maintain integrity in water without being easily broken, thereby extending the suspension time of the feed in water. The biofilm complex forms a three-dimensional network structure in the feed, forming a stable protective layer, so that the slow-sinking fish feed produced has excellent performance in terms of sedimentation rate, water solubility index, hardness and sinking rate.

Description

Technical Field

[0001] The invention relates to the technical field of feed and preparation thereof, and in particular to a slow-sinking fish feed and a preparation method thereof. Background Art

[0002] Traditional aquatic feeds are mainly divided into two categories: floating feeds and sinking feeds. Among them, sinking feeds tend to sink to the bottom of the water quickly after entering the water, and are prone to accumulation, which not only leads to uneven distribution of feed in the water body, but also often causes feed waste and pollutes water quality. On the other hand, although floating feeds float on the water surface, under extreme weather conditions, such as hot summer or cold winter, when the water surface temperature is too high or too low, fish are unwilling to feed on the water surface, which also leads to feed waste and has an adverse effect on water quality.

[0003] In recent years, slow-sinking fish feed, as a new form of feed, has gradually gained favor in the aquaculture industry. Considering the distribution characteristics of fish in the water body, especially those fish that mainly move in the middle and lower layers, the design of slow-sinking fish feed is particularly important. Traditional sinking fish feed often causes the middle and lower layer fish to be unable to fully ingest due to its rapid sinking characteristics, while the lower layer fish may overeat due to feed accumulation. Slow-sinking fish feed carefully controls the sinking speed of the feed so that it can slowly sink in the water body, thereby greatly increasing the contact time between fish and feed and significantly improving the utilization rate of feed.

[0004] The application of slow-sinking fish feed has brought many advantages to the aquaculture industry. First, it improves the uniformity of feed distribution in the water, allowing fish to obtain food more conveniently. Secondly, since the feed is suspended in the water for a longer time, fish have more opportunities to absorb sufficient nutrition, which not only helps to promote the healthy growth and reproduction of fish, but also further improves the overall benefits of the aquaculture industry. In addition, the design of slow-sinking fish feed also effectively reduces feed waste, reduces aquaculture costs, and injects new vitality into the sustainable development of the aquaculture industry. However, since the slow-sinking fish feed is suspended in the water for a long time, it is easy to cause the loss of nutrients, thereby reducing the nutritional value of the feed. Summary of the invention

[0005] In view of this, the present invention provides a slow-sinking fish feed and a preparation method thereof to solve the above problems.

[0006] The technical solution of the present invention is achieved as follows: a slow-sinking fish feed comprises the following raw materials in parts by weight: 30-40 parts of fish meal, 20-30 parts of soybean meal, 10-20 parts of corn flour, 4-6 parts of vegetable oil, 2-4 parts of biofilm complex, 1-3 parts of starch nanocrystals, 0.5-1.5 parts of antibacterial agent, and 0.6-1.2 parts of premix, wherein the biofilm complex is composed of sunflower wax, lignin, and sodium alginate in a mass ratio of (1.0-2.0):(1.0-1.5):(0.8-1.6).

[0007] Furthermore, a slow-sinking fish feed comprises the following raw materials in parts by weight: 35 parts of fish meal, 25 parts of soybean meal, 15 parts of corn flour, 5 parts of vegetable oil, 3 parts of biofilm complex, 2 parts of starch nanocrystals, 1.0 part of antibacterial agent, and 0.9 part of premix, wherein the biofilm complex is composed of sunflower wax, lignin, and sodium alginate in a mass ratio of 1.5:1.3:1.2.

[0008] Furthermore, the vegetable oil is one or a combination of peanut oil, sesame oil, corn oil, rapeseed oil, tea seed oil, sunflower seed oil, palm oil, coconut oil, walnut oil, olive oil, soybean oil, and cottonseed oil.

[0009] Furthermore, the antibacterial agent is one or a combination of phellodendron alkaloids, eugenol, camphor, chrysanthemum lactone, and epoxy-lutein.

[0010] Furthermore, the premix includes the following raw materials in parts by weight: 4-6 parts of vitamin C, 3-4 parts of vitamin B complex, 2-3 parts of vitamin E, 1-2 parts of vitamin A, 0.3-0.7 parts of vitamin D3, 20-24 parts of calcium carbonate, 12-16 parts of monocalcium phosphate, 2-3 parts of magnesium sulfate, 1-2 parts of ferrous sulfate, 0.8-1.2 parts of zinc sulfate, 0.1-0.3 parts of copper sulfate, 0.01-0.03 parts of sodium selenite, 2-4 parts of lysine, 1-2 parts of methionine, and 0.5-1.5 parts of threonine.

[0011] Furthermore, the vitamin B complex is a combination of at least two of vitamin B1, vitamin B2, vitamin B6, and vitamin B12.

[0012] Furthermore, the starch nanocrystals are prepared by the following method: placing the original starch in a blender, and injecting deionized water, the mass volume ratio of the original starch to the deionized water is 1:(8-12) g / mL, stirring at 200-300r / min for 25-35min at 60-70°C to obtain a starch solution, and then adding hydrochloric acid with a concentration of 10-13% to react, the volume ratio of the hydrochloric acid to the starch solution is 1:(6-8), the reaction is reacted at 35-45°C for 4-6h, and the reaction is After the reaction is completed, the solution is placed in a centrifuge, separated at 4000-6000 r / min for 15-20 min and the precipitate is filtered out, the precipitate is washed with deionized water, and after washing, the precipitate is separated at 4000-6000 r / min for 15-20 min and the precipitate is filtered out, the washing is repeated 3 times, the precipitate separated by centrifugation is placed in a dryer and dried at 50-60° C. for 40-48 h, and the dried precipitate is sieved through a 60-100 mesh sieve to obtain starch nanocrystals.

[0013] Furthermore, the native starch is one of cassava starch, corn starch, potato starch, wheat starch, pea starch, sweet potato starch, and kudzu starch.

[0014] Furthermore, a method for preparing a slow-sinking fish feed comprises the following steps:

[0015] S1. Crush the soybean meal and then pass it through a 60-100 mesh sieve;

[0016] S2, weighing fish meal, crushed soybean meal, and corn flour by weight and preliminarily mixing them to obtain a primary mixture;

[0017] S3, adding vegetable oil to the above primary mixture, stirring to obtain a medium mixture;

[0018] S4, adding the biofilm composite, starch nanocrystals, antibacterial agent and premix to the intermediate mixture, and stirring to obtain a final mixture;

[0019] S5, the final mixture is subjected to steam conditioning and then puffing treatment;

[0020] S7. The expanded final mixed material is put into a dryer for drying to obtain a slow-sinking fish feed.

[0021] Furthermore, the S2 preliminary mixing stirring speed is 80-120r / min, and the stirring time is 5-10min, the S3 stirring speed is 150-200r / min, and the stirring time is 10-15min, the S4 stirring speed is 200-300r / min, and the stirring time is 20-30min, the S5 steam pressure is 0.3-0.4MPa, the tempering temperature is 95-100℃, the tempering time is 4-6min, the puffing temperature is 120-130℃, and the puffing coefficient is 1.2-1.3, and the S7 drying temperature is 80-90℃, and the drying time is 20-30min.

[0022] Compared with the prior art, the invention has the following beneficial effects: in the invention, by adding starch nanocrystals, the crystal structure and nanometer size of the starch nanocrystals enable the starch nanocrystals to penetrate into the internal structure of the feed and closely combine with other components in the feed. This combination increases the structural stability and hardness of the feed, so that the feed maintains integrity in water and is not easy to break, thereby prolonging the suspension time of the feed in water. By adding a biofilm composite agent, a film is formed on the surface of the feed, which effectively prevents the dissolution of nutrients. This is because the viscosity of the sodium alginate in the biofilm can make it closely combine with lignin to form a continuous network structure. The film-forming property of sunflower wax can wrap this network structure on the surface of the feed to form a stable protective layer. This protective layer can not only slow down the penetration of water into the feed, but also reduce the dissolution rate of nutrients in water. Therefore, the three-dimensional network structure formed by the interaction of sodium alginate, lignin and sunflower wax can form a stable protective layer, thereby effectively reducing the dissolution of nutrients. The present invention improves the antibacterial property of feed by adding one or more combinations of phellodendron, eugenol, camphor, chrysanthemum lactone and epoxy lutein, so that even if the feed is suspended in water for a long time, the feed will not be corrupted due to bacterial reproduction. Moreover, phellodendron, eugenol, camphor, chrysanthemum lactone and epoxy lutein have anti-inflammatory and antioxidant functions, can improve the immunity and anti-stress ability of fish, and are beneficial to the growth of fish. At the same time, multiple vitamins, trace elements and amino acids are also added to the feed to improve the growth performance of fish and promote the healthy development of fish. DETAILED DESCRIPTION

[0023] In order to better understand the technical content of the present invention, specific embodiments are provided below to further illustrate the present invention.

[0024] Unless otherwise specified, the experimental methods used in the embodiments of the present invention are all conventional methods.

[0025] Unless otherwise specified, the materials, reagents, etc. used in the embodiments of the present invention can be obtained from commercial sources.

[0026] Example 1

[0027] A slow-sinking fish feed comprises the following raw materials in parts by weight: 30 parts of fish meal, 20 parts of soybean meal, 10 parts of corn flour, 4 parts of vegetable oil, 2 parts of biofilm compound, 1 part of starch nanocrystal, 0.5 parts of antibacterial agent, and 0.6 parts of premix, wherein the biofilm compound is composed of sunflower wax, lignin, and sodium alginate in a mass ratio of 1.0:1.0:0.8. The vegetable oil is a 1:1 combination of peanut oil and sesame oil, the antibacterial agent is composed of phellodendron alkaloids and wild chrysanthemum lactones in a mass ratio of 1:1, and the premix includes the following raw materials in parts by weight: 4 parts of vitamin C, 3 parts of complex vitamin B composed of vitamin B1 and vitamin B12 in a 1:1 ratio, 2 parts of vitamin E, 1 part of vitamin A, 0.3 parts of vitamin D3, 20 parts of calcium carbonate, 12 parts of monocalcium phosphate, 2 parts of magnesium sulfate, 1 part of ferrous sulfate, 0.8 parts of zinc sulfate, 0.1 parts of copper sulfate, 0.01 parts of sodium selenite, 2 parts of lysine, 1 part of methionine, and 0.5 parts of threonine.

[0028] The starch nanocrystals are prepared by the following method: cassava starch is placed in a blender, and deionized water is injected at a mass volume ratio of g / mL 1:8 to cassava starch, and stirred at 200r / min for 35min at 60°C to obtain a starch solution. Then, hydrochloric acid with a concentration of 10% and a volume of 6 times that of the cassava starch solution is added to react at 35°C for 6h. After the reaction is completed, the above solution is placed in a centrifuge, separated at 4000r / min for 20min and the precipitate is filtered out. The precipitate is washed with deionized water, separated at 4000r / min for 20min and the precipitate is filtered out after washing, and the washing is repeated 3 times. The precipitate separated by centrifugation is placed in a dryer and dried at 50°C for 48h. The dried precipitate is sieved through a 60-mesh sieve to obtain starch nanocrystals.

[0029] Example 2

[0030] A slow-sinking fish feed comprises the following raw materials in parts by weight: 40 parts of fish meal, 30 parts of soybean meal, 20 parts of corn flour, 6 parts of vegetable oil, 4 parts of biofilm compound, 3 parts of starch nanocrystal, 1.5 parts of antibacterial agent, and 1.2 parts of premix. The biofilm compound is composed of sunflower wax, lignin, and sodium alginate in a mass ratio of 2.0:1.5:1.6. The vegetable oil is a 1:1 combination of sunflower oil and coconut oil, the antibacterial agent is eugenol, and the premix comprises the following raw materials in parts by weight: 6 parts of vitamin C, 4 parts of vitamin B complex composed of vitamin B2 and vitamin B6 in a 1:1 combination, 3 parts of vitamin E, 2 parts of vitamin A, 0.7 parts of vitamin D3, 24 parts of calcium carbonate, 16 parts of monocalcium phosphate, 3 parts of magnesium sulfate, 2 parts of ferrous sulfate, 1.2 parts of zinc sulfate, 0.3 parts of copper sulfate, 0.03 parts of sodium selenite, 4 parts of lysine, 2 parts of methionine, and 1.5 parts of threonine.

[0031] The starch nanocrystals are prepared by the following method: wheat starch is placed in a blender, and deionized water is injected at a mass volume ratio of 1:8 to wheat starch g / mL, and the mixture is stirred at 300 r / min for 25 min at 70°C to obtain a wheat starch solution. Then, hydrochloric acid with a concentration of 13% and a volume of 8 times that of the wheat starch solution is added to react at 45°C for 4 hours. After the reaction, the solution is placed in a centrifuge, separated at 6000 r / min for 15 minutes and the precipitate is filtered out, the precipitate is washed with deionized water, separated at 6000 r / min for 15 minutes and the precipitate is filtered out, the washing is repeated 3 times, the precipitate separated by centrifugation is placed in a dryer and dried at 60°C for 40 hours, and the dried precipitate is sieved through a 100-mesh sieve to obtain starch nanocrystals.

[0032] Next, the slow-sinking fish feed in Example 1 and Example 2 is prepared according to the following method:

[0033] S1. Grind the soybean meal and then pass it through a 60-mesh sieve;

[0034] S2, weighing fish meal, crushed soybean meal, and corn flour by weight and stirring at 80 r / min for 10 min to obtain a primary mixture;

[0035] S3, adding vegetable oil to the above primary mixture, stirring at 150r / min for 15min to obtain a medium mixture;

[0036] S4, adding the biofilm composite, starch nanocrystals, antibacterial agent and premix to the intermediate mixture, stirring at 200 r / min for 30 min to obtain a final mixture;

[0037] S5, the final mixture is tempered by passing steam at a pressure of 0.3 MPa, tempered at 95°C for 6 minutes, and then puffed at 120°C, with a puffing coefficient of 1.2;

[0038] S7. The expanded final mixed material enters a dryer and is dried at 80° C. for 30 minutes to obtain a slow-sinking fish feed.

[0039] Example 3

[0040] A slow-sinking fish feed comprises the following raw materials in parts by weight: 35 parts of fish meal, 25 parts of soybean meal, 15 parts of corn flour, 5 parts of vegetable oil, 3 parts of biofilm compound, 2 parts of starch nanocrystal, 1.0 part of antibacterial agent, and 0.9 part of premix. The biofilm compound is composed of sunflower wax, lignin, and sodium alginate in a mass ratio of 1.5:1.3:1.2. The vegetable oil is a combination of tea seed oil, sunflower seed oil, and palm oil in a ratio of 1:2:1. The antibacterial agent is a combination of phellodendron alkali, camphor, and epoxy lutein in a mass ratio of 1:1:1. The premix includes the following raw materials in parts by weight: 5 parts of vitamin C, 3.5 parts of complex vitamin B composed of vitamin B1, vitamin B2, and vitamin B12 in a ratio of 1:1:1, 2.5 parts of vitamin E, 1.5 parts of vitamin A, 0.5 parts of vitamin D3, 22 parts of calcium carbonate, 14 parts of monocalcium phosphate, 2.5 parts of magnesium sulfate, 1.5 parts of ferrous sulfate, 1.0 part of zinc sulfate, 0.2 parts of copper sulfate, 0.02 parts of sodium selenite, 3 parts of lysine, 1.5 parts of methionine, and 1.0 part of threonine.

[0041] The starch nanocrystals are prepared by the following method: placing kudzu starch in a blender, injecting deionized water at a mass volume ratio of 1:10 to kudzu starch g / mL, stirring at 250r / min for 30min at 65°C to obtain a kudzu starch solution. Then, hydrochloric acid with a concentration of 11.5% and a volume of 7 times that of the kudzu starch solution is added to react at 40°C for 5h. After the reaction is completed, the solution is placed in a centrifuge, separated at 5000r / min for 17.5min and the precipitate is filtered out, the precipitate is washed with deionized water, separated at 5000r / min for 17.5min and the precipitate is filtered out after washing, and the washing is repeated 3 times, and the precipitate separated by centrifugation is placed in a dryer and dried at 55°C for 44h, and the dried precipitate is sieved through an 80-mesh sieve to obtain starch nanocrystals.

[0042] Next, the slow-sinking fish feed of Example 3 is prepared according to the following method:

[0043] S1. Crush the soybean meal and then pass it through an 80-mesh sieve;

[0044] S2. Weigh fish meal, crushed soybean meal, and corn meal by weight and stir at 100 r / min for 7.5 min to perform preliminary mixing to obtain a primary mixture;

[0045] S3, adding vegetable oil to the above primary mixture, stirring at 175r / min for 12.5min to obtain a medium mixture;

[0046] S4, adding the biofilm composite, starch nanocrystals, antibacterial agent and premix to the intermediate mixture, stirring at 250 r / min for 25 min to obtain a final mixture;

[0047] S5, the final mixture is tempered by passing steam at a pressure of 0.35 MPa, tempered at 97.5°C for 5 minutes, and then puffed at 125°C with a puffing coefficient of 1.25;

[0048] S7. The expanded final mixed material enters a dryer and is dried at 85° C. for 25 minutes to obtain a slow-sinking fish feed.

[0049] Example 4

[0050] A slow-sinking fish feed comprises the following raw materials in parts by weight: 30 parts of fish meal, 20 parts of soybean meal, 10 parts of corn flour, 4 parts of vegetable oil, 2 parts of biofilm compound, 1 part of starch nanocrystal, 0.5 parts of antibacterial agent, and 0.6 parts of premix. The biofilm compound is composed of sunflower wax, lignin, and sodium alginate in a mass ratio of 1.0:1.0:0.8. The vegetable oil is soybean oil, the antibacterial agent is wild chrysanthemum lactone, and the premix comprises the following raw materials in parts by weight: 4 parts of vitamin C, 3 parts of vitamin B complex composed of vitamin B1, vitamin B6, and vitamin B12 in a ratio of 1:1:1, 2 parts of vitamin E, 1 part of vitamin A, 0.3 parts of vitamin D3, 20 parts of calcium carbonate, 12 parts of calcium dihydrogen phosphate, 2 parts of magnesium sulfate, 1 part of ferrous sulfate, 0.8 parts of zinc sulfate, 0.1 parts of copper sulfate, 0.01 parts of sodium selenite, 2 parts of lysine, 1 part of methionine, and 0.5 parts of threonine.

[0051] The starch nanocrystals are prepared by the following method: corn starch is placed in a blender, and deionized water is injected at a mass volume ratio of g / mL 1:8 to corn starch, and stirred at 200r / min for 35min at 60°C to obtain a starch solution. Then, hydrochloric acid with a concentration of 10% and a volume of 6 times the corn starch solution is added to react at 35°C for 6h. After the reaction is completed, the above solution is placed in a centrifuge, separated at 4000r / min for 20min and the precipitate is filtered out. The precipitate is washed with deionized water, separated at 4000r / min for 20min and the precipitate is filtered out after washing, and the washing is repeated 3 times. The washed and centrifuged precipitate is placed in a dryer and dried at 50°C for 48h. The dried precipitate is sieved through a 60-mesh sieve to obtain starch nanocrystals.

[0052] Example 5

[0053] A slow-sinking fish feed comprises the following raw materials in parts by weight: 40 parts of fish meal, 30 parts of soybean meal, 20 parts of corn flour, 6 parts of vegetable oil, 4 parts of biofilm compound, 3 parts of starch nanocrystal, 1.5 parts of antibacterial agent, and 1.2 parts of premix. The biofilm compound is composed of sunflower wax, lignin, and sodium alginate in a mass ratio of 2.0:1.5:1.6. The vegetable oil is rapeseed oil, the antibacterial agent is a 1:1 combination of camphor and epoxy lutein, and the premix includes the following raw materials in parts by weight: 6 parts of vitamin C, 4 parts of complex vitamin B composed of vitamin B1, vitamin B2, vitamin B6, and B12 in a ratio of 1:1:1:1, 3 parts of vitamin E, 2 parts of vitamin A, 0.7 parts of vitamin D3, 24 parts of calcium carbonate, 16 parts of monocalcium phosphate, 3 parts of magnesium sulfate, 2 parts of ferrous sulfate, 1.2 parts of zinc sulfate, 0.3 parts of copper sulfate, 0.03 parts of sodium selenite, 4 parts of lysine, 2 parts of methionine, and 1.5 parts of threonine.

[0054] The starch nanocrystals are prepared by the following method: pea starch is placed in a blender, and deionized water is injected according to a mass volume ratio of pea starch g / mL 1:8, and the mixture is stirred at 300r / min for 25min at 70°C to obtain a wheat starch solution. Then, hydrochloric acid with a concentration of 13% and a volume of 8 times that of the pea starch solution is added to react at 45°C for 4h, and after the reaction, the solution is placed in a centrifuge, separated at 6000r / min for 15min and the precipitate is filtered out, the precipitate is washed with deionized water, and after washing, the precipitate is separated at 6000r / min for 15min and the precipitate is filtered out, and the washing is repeated 3 times, and the washed and centrifugally separated precipitate is placed in a dryer and dried at 60°C for 40h, and the dried precipitate is sieved through a 100-mesh sieve to obtain starch nanocrystals.

[0055] Next, the slow-sinking fish feeds of Examples 4 and 5 were prepared according to the following method:

[0056] S1. Crush the soybean meal and then pass it through a 100-mesh sieve;

[0057] S2, weighing fish meal, crushed soybean meal, and corn flour by weight and stirring at 120 r / min for 5 min to obtain a primary mixture;

[0058] S3, adding vegetable oil to the above primary mixture, stirring at 200 r / min for 15 min to obtain a medium mixture;

[0059] S4, adding the biofilm composite, starch nanocrystals, antibacterial agent and premix to the intermediate mixture, stirring at 300 r / min for 30 min to obtain a final mixture;

[0060] S5, the final mixture is tempered by passing steam at a pressure of 0.4 MPa, tempered at 100°C for 4 minutes, and then puffed at 130°C, with a puffing coefficient of 1.3;

[0061] S7. The expanded final mixture is placed in a dryer for drying at 90° C. for 30 minutes to obtain a slow-sinking fish feed.

[0062] Comparative Example 1

[0063] The difference between this comparative example and Example 3 is that the slow-sinking fish feed raw material does not contain starch nanocrystals.

[0064] Comparative Example 2

[0065] The difference between this comparative example and Example 3 is that the slow-sinking fish feed raw material does not contain a biofilm complex agent.

[0066] Comparative Example 3

[0067] The difference between this comparative example and Example 3 is that the biofilm composite agent consists of lignin and sodium alginate in a mass ratio of 1.3:1.2.

[0068] Comparative Example 4

[0069] Compared with Example 3, the difference between this comparative example and Example 3 is that the slow-sinking fish feed includes the following raw materials in parts by weight: 50 parts of fish meal, 35 parts of soybean meal, 25 parts of corn flour, 10 parts of vegetable oil, 1 part of biofilm complex, 4 parts of starch nanocrystals, 2.0 parts of antibacterial agent, and 0.5 parts of premix.

[0070] 1. Feed quality determination

[0071] The quality of the slow-sinking fish feed prepared in Examples 1-5 and Comparative Examples 1-4 was measured, and the specific measurement items were sedimentation velocity, water solubility index, hardness, and water sinking rate. The sedimentation velocity was measured according to the following method:

[0072] 100 grains of slow-sinking fish feed prepared in Examples 1-5 and Comparative Examples 1-4 were randomly taken, and the feed was released from the water surface into a transparent tube with a diameter of 60 mm and a height of 105 cm. Deaerated distilled water was placed in the tube, and the water surface height was 100 cm. The time was measured from the time when the feed began to fall on the water surface, and the time taken for the feed to fall to the bottom of the tube was measured. The calculation of the settling speed of the slow-sinking fish feed is shown in formula (1), and the average value is calculated and recorded in Table 1.

[0073]

[0074] Where v is the sedimentation velocity, in cm / s; H is the water surface height, in cm; T is the time it takes to sink from the water surface to the bottom of the pipe, in seconds.

[0075] The water solubility index is determined by the following method: the slow-sinking fish feed is crushed and passed through a sieve with a mesh size of 0.180 mm, 2.0 g of the sieve is weighed and placed in a centrifuge tube, 20 mL of distilled water is added and the sample is treated using a vortexer, shaken at a speed of 1500 r / min for 20 min, and then centrifuged using a centrifuge and treated at a speed of 3000 r / min for 20 min. The supernatant is slowly poured into a constant weight beaker, and the beaker is dried in an oven at 135°C to a constant weight. The water solubility index is calculated using formula (2). The slow-sinking feed samples prepared in Examples 1-5 and Comparative Examples 1-4 are measured 3 times each, and the average value is calculated and included in Table 1.

[0076]

[0077] Where WSI is the water solubility index, in %; M2 is the total weight of the supernatant after drying and the beaker, in g; M1 is the weight of the beaker, in g; M0 is the sample weight, in g.

[0078] Randomly take 20 slow-sinking fish feeds prepared in Examples 1-5 and Comparative Examples 1-4, measure their hardness using a hardness meter, calculate the average value, and enter it into Table 1.

[0079] The sinking rate is determined by the following method: 200 slow-sinking fish feeds prepared in Examples 1-5 and Comparative Examples 1-4 are randomly taken, placed in distilled water, and stirred slightly for a few times. After the water is still, the number of floating feed particles is counted, which is recorded as the initial sinking rate; after 10 minutes, the number of floating feed particles is counted again, which is recorded as the 10-minute sinking rate. The calculation of the sinking rate is shown in formula (3), and the calculation results of the sinking rate are recorded in Table 1.

[0080]

[0081] Where SA is the sinking rate, unit is %; Q is the total number of feed particles, and Q1 is the number of floating feed particles.

[0082]

[0083]

[0084] It can be seen from Table 1 that the slow-sinking fish feed prepared by the present invention has excellent performance in terms of sedimentation speed, water solubility index, hardness and sinking rate, especially Example 3 has the best effect.

[0085] Comparing Example 3 with Comparative Example 1, the starch nanocrystals in Example 3 can adsorb and fix a certain amount of water molecules when in contact with water, forming a temporary hydration layer. This hydration layer increases the volume and buoyancy of the feed particles, thereby slowing down the sinking speed of the feed. At the same time, the starch nanocrystals also have viscosity and gelling effects, so that the starch nanocrystals form bridges and connections between the feed raw materials, enhance the cohesion between the feed raw materials, and slow down the dissolution of soluble components from the feed. The nanometer size of the starch nanocrystals enables the starch nanocrystals to be filled into the tiny gaps of the feed particles, increasing the density and structural strength of the particles. In addition, the interaction between the nanocrystals and between the nanocrystals and other feed raw materials also enhances the cohesion of the feed, thereby increasing the hardness of the feed. The addition of starch nanocrystals changes the wettability of the surface of the feed particles, helps to reduce the direct scouring effect of the water flow on the feed particles, and enables the feed particles to remain suspended for a longer time and not easily sink. After adding starch nanocrystals, the sedimentation rate slowed down by 14.5%, the water solubility index decreased by 20.9%, the hardness increased by 22.5%, the initial sinking rate decreased by 15.6%, and the 10-minute sinking rate decreased by 8.5%.

[0086] Comparing Example 3 with Comparative Example 2, the viscosity of the sodium alginate in the biofilm composite in Example 3 can make it closely combined with lignin to form a continuous network structure. The film-forming property of sunflower wax can wrap this network structure on the surface of the feed to form a stable protective layer. This protective layer can slow down the penetration of water into the feed, slow down the sedimentation speed and sinking rate of the feed. At the same time, the protective layer can also reduce the dissolution of nutrients in water. The protective layer formed by the combination of lignin, sodium alginate and sunflower wax enables the feed to obtain a harder surface wax layer and a stable internal network structure, thereby increasing the hardness of the feed. Therefore, the three-dimensional network structure formed by the interaction of sodium alginate, lignin and sunflower wax can form a stable protective layer, which makes the fish feed have excellent performance in sedimentation rate, water solubility index, hardness and sinking rate. After adding the biofilm composite agent, the sedimentation rate slowed down by 21.8%, the water solubility index decreased by 31.2%, the hardness increased by 34.9%, the initial sinking rate decreased by 23.0%, and the 10-minute sinking rate decreased by 10.3%.

[0087] Comparing Example 3 with Comparative Example 3, the sedimentation rate of Comparative Example 3 increased by 21.0%, the water solubility index increased by 28.5%, the hardness decreased by 16.8%, the initial sinking rate increased by 25.8%, and the 10-minute sinking rate increased by 5.4%. It can be seen that the lack of sunflower wax in the biofilm composite greatly reduces the performance of the slow-sinking fish feed. Therefore, only when sunflower wax, sodium alginate and lignin are closely matched can the prepared slow-sinking fish feed have excellent performance.

[0088] Comparing Example 3 with Comparative Example 4, Example 3 slowed down the sedimentation rate by 18.3%, reduced the water solubility index by 29.8%, increased the hardness by 29.1%, reduced the initial sinking rate by 21.5%, and reduced the 10-min sinking rate by 7.6%. It can be seen that only when the components are combined in a specific proportion can the maximum value be exerted, and thus a slow-sinking fish feed with better performance can be prepared.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A slow sinking fish feed, characterized in that: The invention comprises the following raw materials in parts by weight: 30-40 parts of fish meal, 20-30 parts of soybean meal, 10-20 parts of corn flour, 4-6 parts of vegetable oil, 2-4 parts of biofilm compound, 1-3 parts of starch nanocrystal, 0.5-1.5 parts of antibacterial agent and 0.6-1.2 parts of premix, wherein the biofilm compound is composed of sunflower wax, lignin and sodium alginate in a mass ratio of (1.0-2.0):(1.0-1.5):(0.8-1.6); the antibacterial agent is one or a combination of phellodendron alkali, eugenol, camphor, wild chrysanthemum lactone and epoxy lutein; the starch nanocrystal is prepared by the following method: placing raw starch in a blender and injecting deionized water, wherein the mass volume ratio of raw starch to deionized water is 1:(8-12) at 60-70°C. The starch solution is stirred at 200-300 r / min for 25-35 minutes to obtain a starch solution, and then hydrochloric acid with a concentration of 10-13% is added for reaction, wherein the volume ratio of the hydrochloric acid to the starch solution is 1:(6-8), and the reaction is carried out at 35-45° C. for 4-6 hours. After the reaction is completed, the solution is placed in a centrifuge, separated at 4000-6000 r / min for 15-20 minutes and a precipitate is filtered out, and the precipitate is washed with deionized water, and after washing, the precipitate is separated at 4000-6000 r / min for 15-20 minutes and the precipitate is filtered out, and the washing is repeated 3 times, and the precipitate separated by centrifugation is placed in a dryer and dried at 50-60° C. for 40-48 hours, and the dried precipitate is sieved through a 60-100 mesh sieve to obtain starch nanocrystals.

2. The slow sinking fish feed according to claim 1, characterized in that: The invention comprises the following raw materials in parts by weight: 35 parts of fish meal, 25 parts of soybean meal, 15 parts of corn flour, 5 parts of vegetable oil, 3 parts of biofilm compound agent, 2 parts of starch nanocrystals, 1.0 part of antibacterial agent and 0.9 part of premix. The biofilm compound agent is composed of sunflower wax, lignin and sodium alginate in a mass ratio of 1.5:1.3:1.

2.

3. A slow sinking fish feed as claimed in claim 1 or 2, characterized in that: The vegetable oil is one or a combination of peanut oil, sesame oil, corn oil, rapeseed oil, tea seed oil, sunflower seed oil, palm oil, coconut oil, walnut oil, olive oil, soybean oil, and cottonseed oil.

4. A slow sinking fish feed as claimed in claim 1 or 2, characterized in that: The premix comprises the following raw materials in parts by weight: 4-6 parts of vitamin C, 3-4 parts of vitamin B complex, 2-3 parts of vitamin E, 1-2 parts of vitamin A, 0.3-0.7 parts of vitamin D3, 20-24 parts of calcium carbonate, 12-16 parts of calcium dihydrogen phosphate, 2-3 parts of magnesium sulfate, 1-2 parts of ferrous sulfate, 0.8-1.2 parts of zinc sulfate, 0.1-0.3 parts of copper sulfate, 0.01-0.03 parts of sodium selenite, 2-4 parts of lysine, 1-2 parts of methionine, and 0.5-1.5 parts of threonine.

5. The slow sinking fish feed according to claim 4, characterized in that: The vitamin B complex is a combination of at least two of vitamin B1, vitamin B2, vitamin B6 and vitamin B12.

6. The slow sinking fish feed according to claim 1, characterized in that: The native starch is one of cassava starch, corn starch, potato starch, wheat starch, pea starch, sweet potato starch and kudzu starch.

7. The method for preparing a slow-sinking fish feed according to claim 1 or 2, characterized in that: The following steps are involved: S1. Crush the soybean meal and then pass it through a 60-100 mesh sieve; S2, weighing fish meal, crushed soybean meal, and corn flour according to weight, and preliminarily mixing them to obtain a primary mixture; S3, adding vegetable oil to the above primary mixture, stirring to obtain a medium mixture; S4, adding the biofilm composite, starch nanocrystals, antibacterial agent and premix to the intermediate mixture, and stirring to obtain a final mixture; S5, the final mixture is subjected to steam conditioning and then puffing treatment; S7. The expanded final mixed material is put into a dryer for drying to obtain a slow-sinking fish feed.

8. The method for preparing a slow-sinking fish feed according to claim 7, characterized in that: The S2 preliminary mixing stirring speed is 80-120r / min, and the stirring time is 5-10min, the S3 stirring speed is 150-200r / min, and the stirring time is 10-15min, the S4 stirring speed is 200-300r / min, and the stirring time is 20-30min, the S5 steam pressure is 0.3-0.4MPa, the tempering temperature is 95-100℃, the tempering time is 4-6min, the puffing temperature is 120-130℃, and the puffing coefficient is 1.2-1.3, and the S7 drying temperature is 80-90℃, and the drying time is 20-30min.

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