Method for manufacturing shrimp feed granules

Abstract

The invention relates to a method for producing shrimp feed granules having a bulk density of at least 550 g / l and a granule diameter of 0.25-5 mm, said method comprising the following steps: providing a biomass product having a water content of at most 10% by weight (calculated as biomass product) and a DHA content of at least 20% by weight (calculated as biomass product); the present invention relates to a method for producing shrimp feed granules comprising the steps of:-preparing a biomass product derived from a microorganism of the Thraustochytriaceae family or Cryptecodininiaceae family,-preparing a mixture comprising 0.1-10% by weight (calculated on the dry weight of shrimp feed granules) of said biomass and the balance of further feed components,-subjecting the mixture thus obtained to a granule pressing step, the bulk density is at least 550 g / l, and the particle diameter is 0.25-5 mm. It has been found that the addition of a specified biomass product in a specified amount to a composition provided to a pellet press enables shrimp feed pellets with desired properties to be obtained in a single-step granulation process. The addition of the biomass product to the composition for pellet compression results in less or no degradation of DHA compared to the addition of fish oil. It also does not result in excessive lubrication of the pellet press.

Description

[0001] The present invention relates to a method for manufacturing shrimp feed pellets, and shrimp feed pellets obtainable by the method.

[0002] In shrimp aquaculture, shrimp are provided with feed to meet their nutritional requirements. However, in order for shrimp to benefit from their feed to the greatest extent, shrimp feed pellets need to meet many physical requirements in addition to their nutritional requirements. Shrimp are bottom-dwelling animals and they consume their feed by gnawing on pellets. This means that in order for shrimp to be able to access the pellets, the pellets should not float on the water surface, but should sink below the water surface relatively quickly after feeding. In addition, since shrimp will not feed on broken pellets, shrimp feed pellets should have a relatively high stability in the water, that is, they should not break too quickly after feeding. In addition, in view of the above-mentioned gnawing pellets, the pellets must have a uniform nutrient distribution, otherwise the feed gnawing from the core of the pellet will have a different composition from the feed gnawing from the outer layer of the pellet. In order to evenly feed the pellets in the shrimp feed basin, the shrimp feed pellets should not be too large. The appropriate particle size is 0.25-5mm in diameter. This relatively small particle size means that the outer surface of the pellet is relatively large, which brings additional challenges to the pursuit of pellets with relatively high water stability.

[0003] In the art, shrimp feed pellets are usually manufactured by extrusion or using a pellet press. Although extrusion is a flexible and attractive way to manufacture feed pellets, it has the disadvantage of requiring a large investment in equipment and operating costs. Pellet presses have the advantages of simple operation and low capital investment. However, it has been found that not all feed ingredients are readily compatible with pellet pressing.

[0004] One ingredient that often causes problems in manufacturing shrimp feeds that meet the desired properties is unsaturated fatty acids such as DHA in fish oil. It has been found that when fish oil high in DHA is added to a composition provided to a pellet press, the DHA content in the final pellets is lower than the DHA content of the feed before pelleting due to degradation of DHA during pretreatment and compression under the prevailing conditions of the manufacturing process, including high temperatures and high moisture content. Another problem is that the addition of oil to the composition provided to the pellet press may result in over-lubrication of the pellet press, which may lead to clogging of the pellet press, formation of pellets of different sizes and shapes, agglomeration of pellets, and lack of mixing uniformity.

[0005] This problem is usually solved by adding low-quality fish oil to the feed to be pelletized and then impregnating it with an oil with a high DHA content. However, this process has many disadvantages. Firstly, it requires an additional processing step with associated additional equipment and operating costs. Secondly, there is a risk that the oil with a high DHA content is non-uniformly distributed in the final pellets, resulting in uneven feeding of the shrimp. In addition, the impregnation of the pelletized pellets, especially the relatively high density pelletized pellets required to obtain the necessary sinking behavior, is usually incomplete, resulting in the presence of oil on the outside of the pellets. This in turn may cause the pellets to agglomerate and affect the storage properties of the shrimp feed.

[0006] There is a need in the art for a method of making shrimp feed pellets by pellet pressing process which can produce shrimp feed pellets with desirable nutritional and physical properties without the disadvantages of known processes. The present invention provides such a method.

[0007] The present invention relates to a method for producing shrimp feed pellets having a bulk density of at least 550 g / l and a particle diameter of 0.25-5 mm, the method comprising the following steps

[0008] - providing a biomass product having a water content of at most 10% by weight (calculated on the biomass product) and a DHA content of at least 20% by weight (calculated on the biomass product), the biomass product being derived from a microorganism of the family Thraustochytriaceae or the family Cryptecondiniaceae,

[0009] - preparing a mixture comprising 0.1-10 wt% (calculated on the dry weight of shrimp feed pellets) of said biomass and the remainder being other feed ingredients,

[0010] - The mixture thus obtained is subjected to a granulation step to form shrimp feed granules having a bulk density of at least 550 g / l and a granule diameter of 0.25-5 mm.

[0011] It has been found that adding a biomass product as described above in a specified amount to a composition provided to a pellet press enables shrimp feed pellets with desired properties to be obtained in a single step pelleting process. Adding a biomass product to the composition for pellet pressing results in less or no degradation of DHA compared to adding fish oil. It also does not result in over-lubrication of the pellet press.

[0012] The invention also relates to shrimp feed pellets obtainable using the method of the invention.

[0013] Therefore, the present invention also relates to compressed shrimp feed pellets having a bulk density of at least 550 g / l and a particle diameter of 0.25-5 mm, comprising 0.1-10 wt. % of a biomass product (calculated on the dry weight of the shrimp feed pellets), the biomass product having a water content of up to 10 wt. % (calculated on the biomass) and a DHA content of at least 20 wt. % (calculated on the biomass), the biomass being derived from a microorganism of the family Thraustochytriaceae or the family Cryptecondiniaceae.

[0014] The invention, its specific embodiments and further advantages thereof are discussed in more detail below.

[0015] The present invention utilizes a biomass product having a water content of at most 10% by weight (calculated on the biomass product) and a DHA content of at least 20% by weight (calculated on the biomass product), the biomass product originating from a microorganism of the Thraustochytriaceae family or the Cryptecondiniaceae family.

[0016] The biomass is derived from a microorganism of the Thraustochytriaceae family or the Cryptecondiniaceae family. The microorganism of the Thraustochytriaceae family is preferably from the genus Schizochytrium (e.g. S. aggregatum), the genus Thraustochytrium (e.g. T. multirudimentale and T. striatum), the genus Aurantiochytrium (e.g. A. limacinum and A. mangrovei), or the genus Ulkenia (e.g. U. visurgensis and U. amoeboidea). The microorganism of the Crypthecodiniaceae family is preferably from the genus Crypthecodinium.

[0017] In one embodiment, Schizochytrium limacinum or Aurantiochytrium limacinum is used.

[0018] In the context of the present specification, the biomass product is dried biomass.Dried biomass can be obtained, for example, by subjecting a fermentation medium comprising microorganisms of the Thraustochytriaceae family or the Cryptecondiniaceae family to a drying step, such as a spray drying step.

[0019] The biomass product used in the present invention has a water content of at most 10% by weight. Too high a water content will adversely affect the manufacturing process, the physical properties of the particles obtained by the process, and the properties of the particles, including their storage stability. The water content of the biomass product is preferably less than 8% by weight, particularly less than 6% by weight, more particularly less than 4% by weight, still more particularly less than 2% by weight, and in some embodiments less than 1% by weight.

[0020] Water content is determined by Karl Fischer titration. The Karl Fischer procedure is a volumetric titration process for quantitatively determining the water content in liquid and solid samples. The titration is carried out using titrant Hydranal Composite 2 (a single-component reagent that already contains all reactants, including iodine, sulfur dioxide, and bases imidazole and 2-methylimidazole). The titration medium used is a mixture of dry dichloromethane (DCM) and dry methanol (ratio 75 / 25% v / v). The endpoint is determined using a bivoltammetric indicator, that is, the potential at the polarized double platinum needle electrode drops below a certain value, for example, for a Mettler Toledo V30 KF Titrator with a DM143-SC electrode and a polarization current set to 24.0 μA, the value is 100.0 mV.

[0021] The amount of water in the sample can be determined by the amount of reagent added.

[0022] The biomass product has a DHA content of at least 20% by weight.

[0023] The dried biomass can, for example, contain at least 25 wt % DHA, at least 30 wt % DHA, at least 35 wt % DHA, at least 40 wt % DHA, at least 45 wt % DHA, or optionally contain 20 wt % to 50 wt % DHA, 20 wt % to 45 wt % DHA, or 25 wt % to 35 wt % DHA, or 25 wt % to 45 wt % DHA, based on the dry weight of the biomass.

[0024] In the method according to the invention, the biomass product is added to the shrimp feed pellets in an amount of 0.1-10% by weight, calculated on the dry weight of the shrimp feed pellets.

[0025] If the amount of biomass product is too low, the beneficial effect of adding biomass product to feed processing cannot be obtained, nor can the effect of adding DHA to shrimp feed be obtained. Preferably, the biomass product is added to the shrimp feed pellets in an amount of at least 0.3% by weight, in particular at least 0.5% by weight, and in some embodiments at least 1.0% by weight. If the amount of biomass product is too high, overlubrication may occur during processing, and the amount of biomass containing DHA in the feed may be too high, leaving insufficient space for other components of the shrimp feed. Preferably, the biomass product is added to the shrimp feed pellets in an amount of at most 8% by weight, in particular at most 6% by weight, in some embodiments at most 5% by weight, at most 3% by weight, or at most 2% by weight. The range of 0.5-2% by weight can be mentioned as preferred.

[0026] From a nutritional perspective, shrimp feed pellets will typically contain the following ingredients, calculated on a pellet dry weight basis:

[0027] - Protein, usually in an amount of 30-50% by weight

[0028] - Carbohydrates, usually in an amount of 5-40% by weight

[0029] -Lipids, usually in an amount of 5-15% by weight

[0030] - ash, usually in an amount of 3-15% by weight

[0031] The feed usually has an energy content of 250-450 Kcal / 100 g feed.

[0032] In shrimp feed manufacturing, suitable components for providing various nutritional elements are known and need not be further elucidated here. They include, for example, vegetable products such as vegetable oils, soybean meal, corn meal, corn protein and other vegetable products, animal products such as beef tallow and poultry products, fish meal and fish oil.

[0033] In the method according to the invention, various feed components including a biomass product are combined to form a mixture, which is subjected to a pellet pressing step to form shrimp feed pellets having a bulk density of at least 550 g / l and a particle diameter of 0.25-5 mm.

[0034] Pellet compression is known in shrimp feed manufacturing. The general process is described below.

[0035] In the first step, a mixture comprising the various feed ingredients is prepared. There may be a grinding step to ensure the desired particle size of the various ingredients. Water or other liquids may be added to obtain a granulatable mixture, which is usually called a paste.

[0036] The pelletizable mixture or paste usually undergoes a pre-treatment step. In pre-treatment, the pelletizable mixture is kept at a temperature above 70°C, such as 80-98°C or 85-95°C, for 1-10 minutes, such as 1-3 minutes, at a desired moisture content. Moisture can be added to the feed in the form of liquid, steam or both. Pre-treatment is performed for a variety of reasons, including cooking the feed ingredients to improve the digestibility and binding properties of the feed ingredients, ensuring a moisture content that can be pelletized. Pre-treatment is usually performed under mixing, which means that the mixing step and the pre-treatment step can be combined.

[0037] The pre-treated feed mixture is then provided to a pellet press which converts it into pellets. Pellet pressing is typically carried out at a temperature of 50-100° C., in particular 60-100° C., such as 70-90° C. The pelletized product is then cooled to room temperature.

[0038] The moisture content of the final shrimp feed pellets is typically in the range of 0-25 wt%, particularly 0-15 wt%, more particularly 5-10 wt%.If desired, a drying step may be performed.

[0039] The pellet pressing step produces shrimp feed pellets. Post-impregnation or coating with other shrimp feed ingredients may be present but is generally not necessary.

[0040] The invention also relates to shrimp feed pellets obtainable by the process according to the invention.

[0041] Therefore, the present invention also relates to compressed shrimp feed pellets having a bulk density of at least 550 g / l and a particle diameter of 0.25-5 mm, comprising 0.5-10 wt. % of a biomass product (calculated on the dry weight of the shrimp feed pellets), the biomass product having a water content of up to 10 wt. % (calculated on the biomass) and a DHA content of at least 20 wt. % (calculated on the biomass), the biomass being derived from a microorganism of the family Thraustochytriaceae or the family Cryptecondiniaceae.

[0042] The bulk density of the granules is defined as the dry weight of the granules in a certain volume divided by the weight of the granules determined in 1 liter volume.

[0043] The bulk density of the shrimp feed pellets according to the invention is at least 550 g / l. If the bulk density is below this value, the sinking behavior of the pellets is insufficient. Preferably the bulk density is at least 600 g / l, in some embodiments at least 650 g / l. Typically, the bulk density is at most 1000 g / l, in particular at most 900 g / ml, more particularly at most 800 g / ml. The bulk density is necessary in order to have the desired sinking behavior. As mentioned above, shrimps are benthic animals and require fast sinking of the pellets to ensure that the feed reaches the shrimps as quickly as possible.

[0044] The particle diameter of the shrimp feed particles according to the present invention is 0.25-5 mm.

[0045] The particle diameter is the diameter of the particle on its longest axis. The particle can have any shape as long as it can be manufactured by particle pressing. Examples of suitable shapes are cylinders, spheres, sheets and rods, preferably cylinders. In one embodiment, the height to diameter of the particle ranges from 1:5 to 5:1, particularly from 1:3 to 3:1, more particularly from 1:2 to 2:1.

[0046] A feature of the shrimp pellet feed according to the invention is that the biomass product, and in particular the DHA present therein, is evenly distributed in the pellet. This means that shrimps feeding on the pellets will ingest the same percentage of DHA, whether they feed from the core of the pellet or from the surface of the pellet. This in turn makes the shrimp more homogeneous in quality.

[0047] This parameter can be quantified as follows: the ratio of the DHA content in a sample taken from the core of the particle to the DHA content in a sample taken from the outer layer of the particle is between 0.8:1 and 1:0.8, in particular between 0.9:1 and 1:0.9.

[0048] The shrimp feed pellets of the present invention typically have a pellet durability index, also expressed as PDI (pellet durability index) or Holmen pellet durability test, of at least 80%, more particularly at least 85%, still more particularly at least 90%. The Holmen durability test simulates the degradation that pellets undergo during transportation and handling. The determination of this parameter is known to those skilled in the art.

[0049] The present invention also relates to a method for raising shrimps, characterized in that the shrimp feed particles of the present invention are used to feed the shrimps.

[0050] It will be obvious to a person skilled in the art that different embodiments of the invention can be combined unless they are mutually exclusive. Preferences discussed in the context of products also apply to methods and vice versa.

[0051] Unless otherwise indicated, all percentages used herein are weight percentages. When amounts, concentrations, sizes and other parameters are expressed in the form of ranges, preferred ranges, upper limits, lower limits or preferred upper limits and preferred lower limits, it should be understood that any range obtained by combining any upper limit or preferred value with any lower limit or preferred value is also specifically disclosed, regardless of whether the obtained range is explicitly mentioned in the context.

[0052] The present invention is illustrated by the following examples, but the present invention is not limited thereto.

[0053] Example 1: Stability of DHA in Granular Compressed Granules

[0054] Feed ingredients including biomass containing DHA are combined to form a feed mixture. The biomass containing DHA is a dry biomass of the species Schizochytrium having a water content of less than 1% by weight and a DHA content of 33% by weight. The biomass containing DHA is added to the feed composition in an amount of 1%, 2%, 3% or 5% by weight, respectively. The DHA content in the feed is 0.3%, 0.6%, 0.9% and 1.5% by weight, respectively.

[0055] The feed composition was brought to 75°C in 80 seconds and to 90°C in 110 seconds (time from room temperature) in the feed preconditioner. The fatty acid composition in the feed was determined using gas chromatography with flame ionization. It appears that for all samples, the amount of DHA in the sample after the preconditioning step was the same as the amount of DHA before the preconditioning step. No degradation was observed. This is in contrast to the case of using fish oil containing DHA, which is known to degrade under preconditioning conditions.

[0056] Example 2: DHA stability in granular compressed granules - retention time

[0057] DHA stability was determined using a batch preconditioner with 20 kg of ground feed ingredients, including the biomass described in Example 1. Three experiments were conducted, with biomass incorporated at 1 wt%, 3 wt% and 5 wt%. The batches were conditioned at 90°C and samples were taken after 1 minute, 3 minutes and 5 minutes and the DHA content was determined. The results are shown in the following table:

[0058]

[0059] * not determined

[0060] It can be seen that the degradation of DHA is very limited after conditioning at 90°C for 1 minute, 3 minutes or 5 minutes.

Claims

1. A method for producing shrimp feed pellets having a bulk density of at least 550 g / l and a particle diameter of 0.25-5 mm, the method comprising the following steps - providing a biomass product having a water content of at most 10% by weight (calculated on the biomass product) and a DHA content of at least 20% by weight (calculated on the biomass product), the biomass product being derived from a microorganism of the family Thraustochytriaceae or the family Cryptecondiniaceae, - preparing a mixture comprising 0.1-10 wt% (calculated on the dry weight of shrimp feed pellets) of said biomass and the remainder being other feed ingredients, - Subjecting the thus obtained mixture to a pellet pressing step to form shrimp feed pellets having a bulk density of at least 550 g / l and a particle diameter of 0.25-5 mm.

2. The method according to claim 1, wherein the biomass product is derived from Schizochytrium limacinum or Aurantiochytrium limacinum.

3. The method according to any one of the preceding claims, wherein the water content of the biomass product is less than 8 wt%, in particular less than 6 wt%, more particularly less than 4 wt%, still more particularly less than 2 wt%, and in some embodiments less than 1 wt%.

4. The method of any of the preceding claims, wherein the biomass product comprises, calculated on a dry biomass basis, at least 25 wt% DHA, at least 30 wt% DHA, at least 35 wt% DHA, at least 40 wt% DHA, at least 45 wt% DHA, or optionally 20 to 50 wt% DHA, or 20 to 45 wt% DHA, or 25 to 35 wt% DHA, or 25 to 45 wt% DHA.

5. The method according to any one of the preceding claims, wherein the biomass content of the shrimp feed pellets is at least 0.3 wt%, in particular at least 0.5 wt%, in some embodiments at least 1.0 wt%, or at most 6 wt%, in some embodiments at most 5 wt%, at most 3 wt%, or at most 2 wt%, for example in the range of 0.5-2 wt%.

6. A method according to any one of the preceding claims, wherein the shrimp feed pellets comprise the following ingredients, calculated on a pellet dry weight basis: - Protein, in an amount of 30-50% by weight - Carbohydrates in an amount of 5-40% by weight - lipids, in an amount of 5-15% by weight - Ash content, in an amount of 3-15% by weight.

7. A compressed shrimp feed pellet having a bulk density of at least 550 g / l and a particle diameter of 0.25-5 mm, comprising 0.1-10 wt. % of a biomass product (calculated on the dry weight of the shrimp feed pellet), the biomass product having a water content of up to 10 wt. % (calculated on the biomass) and a DHA content of at least 20 wt. % (calculated on the biomass), the biomass being derived from a microorganism of the family Thraustochytriaceae or the family Cryptecondiniaceae.

8. Particle compressed shrimp feed pellets obtained by the method according to any one of claims 1-6.

9. The pelletized compressed shrimp feed pellet according to claim 7 or 8, having a bulk density of at least 600 g / l, in some embodiments at least 650 g / l and / or at most 1000 g / l, in particular at most 900 g / ml, more in particular at most 800 g / ml.

10. The pelletized compressed shrimp feed pellet according to any one of claims 7 to 9, which is a cylinder, a sphere, a sheet or a rod, preferably a cylinder, wherein the height to diameter of the pellet is in the range of 1:5 to 5:1, particularly 1:3 to 3:1, more particularly 1:2 to 2:

1.

11. The pelletized shrimp feed pellet according to any one of claims 7 to 10, wherein the ratio of the DHA content in the sample collected from the core of the pellet to the DHA content in the sample collected from the outer layer of the pellet is between 0.8:1 and 1:0.8, in particular 0.9:1 to 1:0.

9.

12. The pelletized compressed shrimp feed pellet according to any one of claims 7 to 11, having a pellet persistence index of at least 80%, in particular at least 85%, more in particular at least 90%.

13. A method for raising shrimps, wherein the shrimps are fed with the shrimp feed pellets according to any one of claims 7 to 12 during at least a part of their life cycle.

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