METHOD AND SYSTEM FOR PRODUCING AQUACULTURE
20180289040 ยท 2018-10-11
Inventors
Cpc classification
A23K50/80
HUMAN NECESSITIES
B29C48/12
PERFORMING OPERATIONS; TRANSPORTING
B29C48/345
PERFORMING OPERATIONS; TRANSPORTING
B29C48/92
PERFORMING OPERATIONS; TRANSPORTING
B29C2948/92723
PERFORMING OPERATIONS; TRANSPORTING
B29C2948/92971
PERFORMING OPERATIONS; TRANSPORTING
Y02A40/818
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
International classification
A23K50/80
HUMAN NECESSITIES
Abstract
The method and system produces a high-moisture aquatic feed that is stable in water and has a texture that more closely resembles naturally-occurring aquatic feedstocks. The system includes a tempering unit that is structured to allow an operator to control the temperature of a low-carbohydrate high-moisture extrudate after the extrudate leaves a conventional extruder. As the extrudate flows through a tubular matrix within the tempering unit, expansion of the extrudate is controlled to produce the high-moisture water-stable aquafeed.
Claims
1-22. (canceled)
23. A method of producing water-stable aquafeed, the method comprising the steps of: (a) preparing a raw mix; (b) depositing the raw mix into an extruder; (c) providing a tempering unit that is attached to the extruder; (d) positioning a tubular insert within the tempering unit, the tubular insert receiving an extrudate from the extruder and controlling an expansion of the extrudate; (e) circulating a tempering fluid around the tubular insert and thereby controlling cooling a temperature of the extrudate as it moves through the tubular insert; and, (f) producing the water-stable aquafeed from the tubular insert within the tempering unit.
24. The method of claim 23 wherein, in step (a), the raw mix comprises 40-80% liquid so that the water-stable aquafeed produced in step (f) is a high-moisture water-stable aquafeed.
25. The method of claim 23 wherein, after step (f), the high-moisture water-stable is ground or shredded to sizes of 10 microns to 1000 microns suitable for larval aquatic animals.
26. The method of claim 23 wherein, after step (f), the high-moisture water-stable aquafeed is dried to less than 10% moisture.
27. The method of claim 26 wherein after the high-moisture water-stable aquafeed is dried to less than 10%, it is rehydrated so that the rehydrated product has essentially a same cut force/structural integrity value (as measured by a water stability test) as exhibited by high-moisture aquafeed that has not been previously dried.
28. The method of claim 27 wherein the dried high-moisture aquafeed is rehydrated in a vitamin/amino acid solution.
29. A method of producing a high-moisture water-stable aquafeed comprising attaching a tempering unit to an extruder, the tempering unit controlling the temperature, pressure, and expansion rate of extrudate so that high-moisture water-stable aquafeed is produced from the tempering unit.
30. The method of claim 29 wherein the high-moisture water-stable aquafeed is produced without a starch binder.
31. The method of claim 29 wherein the tempering unit comprises a tubular insert, the tubular insert comprising at least one tube.
32. The method of claim 31 wherein the tempering unit comprises a circulating system circulating a tempering fluid around the at least one tube.
33. The method of claim 29 wherein after the high-moisture water-stable aquafeed is produced, the aquafeed is subject to one of drying, grinding, shredding, freezing, or forming.
34. A water-stable aquafeed product produced by the method of claim 23.
35. A high-moisture water-stable aquafeed product produced by the method of claim 24.
36. A high-moisture water-stable aquafeed produced by the method of claim 29.
37. A high-moisture water-stable aquafeed produced by the method of claim 30.
38. A high moisture water-stable aquafeed produced by the process of hydrating a dry mix in the extruder and producing an extrudate out of the extruder and into a tempering unit so that the temperature of the extrudate is decreased in the tempering unit, and producing the high moisture water-stable aquafeed out of the tempering unit.
39. The aquafeed product of claim 38 wherein the high moisture water-stable aquafeed contains no or an ineffective amount of starch as a binder.
40. The aquafeed product of claim 38 wherein the aquafeed product may include one or more of the following: wheat gluten, hill meal, squid meal, fish meal, soy protein products, oilseed protein products, corn gluten, corn gluten meal, pea or other legume protein products, grain products, mixed nut meal, poultry by-product meal, fish oil or any oil energy source, algae, vitamins and minerals.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0011]
[0012]
[0013]
[0014]
[0015]
[0016]
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0017] The present invention comprises a method and apparatus for producing a feed for aquatic organisms.
[0018] For the purpose of this disclosure, a water-stable aquafeed comprises an aquafeed with a percentage of dry weight retained value of greater than 25%, as measured using the water stability test. The water stability test is defined below. Data generated based on the water stability test is shown in Table 2 and graphically illustrated in
[0019] For the purpose of this disclosure, a water-stable aquafeed may alternatively be defined as comprising an aquafeed with a maximum cut force of greater than 10 g/mm.sup.2 after being submersed in water for 1 hour, as measured using the post-submersion structural integrity test. The post-submersion structural integrity test is defined below. Data generated based on the post-submersion structural integrity test is shown in Table 3 and graphically illustrated in
[0020] For the purpose of this disclosure, a high-moisture aquafeed comprises an aquafeed wherein, at the time the aquafeed leaves a tempering unit, the aquafeed product comprises at least 45% by weight liquid. The high-moisture aquafeed comprises only an ineffective amount of starch as a binder.
[0021] Note that the moisture content of the high-moisture aquafeed is determined at the time that the aquafeed emerges from the tempering unit. In a post-production process, the high-moisture aquafeed may be dried for shipment or storage. The dried high-moisture aquafeed can be rehydrated prior to use. After rehydration, the high-moisture aquafeed recovers the elasticity and water stability characteristics of the feed prior to drying.
[0022] For the purpose of this disclosure, conventional feed comprises an aquafeed that is produced by low moisture extrusion (without the use of a tempering unit, or the like), uses starch as a binder, has a hard porous texture, and has a moisture content of less than 10% moisture.
[0023] As shown in
[0024] Table 1 shows the general composition of high-moisture feeds (described herein), and conventionally produced dry feeds, as well as the general composition fish flesh (Atlantic salmon) commonly found in the natural environment. Note that values in Table 1 are expressed as a percentage of dry matter (exclusive of moisture). Where multiple measurements were conducted, average values are shown.
[0025] Results show that conventional feed has a starch content of 13.70%. By contrast, high-moisture feeds contain less than 5% starch, because no starch is used as a binder. Interestingly, there is no difference in non-starch carbohydrate, which is basically cell wall material. Because of the starch difference, the total carbohydrate in high-moisture feed is significantly lower than the conventional feed. Also, compared to conventional feed, high-moisture feed is high in protein and low in oil, although oil can be added by a post-process procedure.
TABLE-US-00001 TABLE 1 Chemical composition of aquafeeds made by the invented method as compared to control feeds Non- Total starch Feed sample Moisture Protein Oil Ash CHO Starch CHO Fresh salmon 68.68 62.91 20.96 8.06 8.07 Conventional 5.85 50.08 15.60 7.41 26.92 13.70 13.07 feed (dried) High-moisture feed (as is) Strand 53.56 66.71 9.82 6.24 17.24 4.46 12.78 Pellets 56.33 66.41 10.00 6.09 17.50 4.58 12.91 Bar 55.73 71.25 5.75 5.29 17.72 3.84 13.89
[0026] After the dry mix is prepared, the mix is placed in a commercial extruder, as described in the second step 12 shown in
[0027] As the extruder processes the mix, pressurized water is injected into the extruder mixing section, or immediately prior to the mixing section. A water injection pump is calibrated and designed to inject an amount of water into the mix so that the hydrated mixture comprises about 40-80% moisture. Alternatively, a pre-calculated amount of water can be incorporated into the raw mix before extrusion and, in this case, no injection pump is needed.
[0028] In the preferred embodiment, the hydrated mixture comprises about 50-70% (preferably 60%) moisture. Note that conventionally-produced fish feed generally comprises about 15-35% moisture during processing and less than 10% moisture after drying. Most actual fish flesh comprises about 75% moisture. The relatively high moisture content of the final product (produced in accordance with the current method) is due to the injection of a metered amount of water into the barrel of the extruder, or the addition of a calculated amount of water to the mix prior to extrusion.
[0029] As shown in
[0030] After the extrudate passes through the distribution plate aperture 26, the extrudate is forced into the tubular insert 28. In the preferred embodiment, the tubular insert 28 comprises a matrix of multiple elongated tubes 30. The tubes 30 are connected by (at least) proximal 31 and distal 32 end plates. For the sake of simplicity, only one exemplary tube 30 is shown in
[0031] By controlling the temperature and flow rate of the tempering fluid within the temping unit 20, an operator can precisely control the temperature of the extrudate within the tempering unit 20. The optimal temperature of the extrudate within the tempering unit varies depending upon the feed formulation, feed rate of the mix, hydroscopic properties of the mix, and the desired characteristics of the final product.
[0032] Similarly, the pressure of the extrudate within the tempering unit 20 is controlled primarily by the flow capacity of the extruder relative to the size and nature of the elongated tubes 30 within the tempering unit 20. Constricting the movement of extrudate out of the tempering unit 20 (via nozzles or the like) increases the pressure on the extrudate within the tempering unit 20. Similarly, for fixed dimensions within the tempering unit 20, increasing the output rate of the extruder (via an increase in screw speeds or the like) also increases pressure within the tempering unit 20.
[0033] By controlling the extrudate pressure (via the extrudate flow rate or by other means) within the tempering unit, an operator at least partially controls the moisture level of the extrudate (and ultimately the aquafeed product) by preventing the uncontrollable loss of moisture through the flashing process. Controlling the pressure within the tubular insert has the effect of controlling the expansion rate of the extrudate within the tubular insert. In the preferred embodiment, the temperature of the extrudate within the tempering unit 20 varies between 5 and 150 C. After passing through the distal end plate 32, the final aquafeed product streams out of the tempering unit 20 in the direction of the arrow 24.
[0034] In alternative embodiments, the tubes 30 may have a variety of shapes, consistent with the shape of the desired final product. For example, the circular tubes 30 shown in
[0035] Similarly,
[0036] Although the method and apparatus are described herein with reference to a preferred embodiments, multiple alternative embodiments may also exist. For example, although the tubes 30 shown in
[0037] During the production of conventional (low-moisture) aquafeed, the raw mix is extruded directly from the extruder barrel (without the benefit of the controlled cooling and expansion provided by the tempering unit described herein). As a part of the conventional mixing process, the mix is pressurized within the extruder barrel so that there is a sudden pressure drop as the mix emerges from the extruder. The pressure drops causes the extrudate to expand rapidlywhich results in an increase in the porosity and the volume of the extrudate product. Carbohydrate is required in the raw mix to effectively bind the produced extrudate into a discrete form. The carbohydrate binder used in prior art processes effectively forms the extrudate into a matrix that allows for the absorption of oil and traps air bubbles so that pellets produced from the conventionally-formed extrudate float.
[0038] By contrast, in accordance with the method described herein, the current process begins in the extruder with much higher moisture levels than used for conventional feeds. As the extrudate leaves the extruder and enters the tempering unit 20, the temperature and pressure drop is controlled and gradual (unlike prior art processes) so that there is no uncontrolled expansion of the extrudate and moisture is not uncontrollably lost through the flashing process. The controlled cooling of the extrudate prevents the formation of relatively large air pockets within the extrudate and results in a retention of moisture, a smooth surface (i.e. a lack of porosity) and a stable texture of the extrudate.
[0039] Because the extrudate expansion is controlled through cooling and a relatively slow pressure release (unlike the conventional process), the addition of a supplemental binding agent (such as starch) is not required. The resulting aquaculture feed product has a texture that is smooth (not porous), fibrous, and has a generally elastic (almost gummy) feel that more closely resembles the texture of natural aquatic foods (such as bait fish). Additionally, upon submersion in water, aquatic feed produced by the current process retains its structural cohesion for an extended amount of time.
PostProduction Processing
[0040] As shown in
[0041] The final aquafeed product may also be dried, refrigerated, or frozen for later use. The high-moisture particles can be dried to less than 10% moisture. The particles may then be ground and sifted to appropriate sizes, and then stored and shipped. The particles can then be rehydrated on-site in a vitamin/amino acid solution to further enhance the content of water soluble nutrients and thereby restore the particle's soft texture and elastic structural integrity.
[0042] The aquafeed product can also be formed (preferably) immediately after it emerges from the tempering unit. A forming unit or multi-knife cutter-head may be attached onto the end plate 32 of the tempering unit 20 to form the aquatic feed product into a variety of forms.
Water Stability Tests and Data
[0043] One means (described in greater detail below) used by the industry to determine water-stability comprises a water stability test. For the purposes of this disclosure, the water stability test comprises a process wherein a subsample of the aquafeed product is dried and weighed before and after the product is submersed in an agitated water bath for 24 hours at room temperature. A final dry weight of the product (after soaking in the agitated bath) is compared to the initial dry weight ((final dry weightdivided byinitial dry weight)*100) to determine a percentage of weight retained. As shown in Table 2 below, the percentage of weight retained value for conventional aquafeeds is about 17%, while the percentage of weight retained for the high-moisture feeds is greater than 70%.
[0044] For the purpose of this disclosure, a water-stable aquafeed comprises an aquafeed with a percentage of weight retained value of greater than 25%, as measured using the water stability test described herein.
[0045] With regard to the specifics of the water stability test used to generate the data presented in Table 2, three types of feed were tested: (1) a bar type high-moisture feed (26 mm wide, 13 mm thick and 70 mm long); (2) a strand type high-moisture feed (3.5 mm in diameter); (3) and a conventionally-produced dry pellet (also 3.5 mm in diameter). One hundred grams of each material was placed in a 500 ml beaker and filled with water to 500 ml. The beakers were placed in a shaking water bath held at 20 C. and shaken at 85 rpm for 24 hours. The samples were removed, drained of water, and sifted through a 2.7 mm screen with light rinsing and then dried at 60 C. for 24 hours, followed by 80 C. for an additional 24 hours. The material was then weighed and the percentage of dry weight retained calculated. The results are shown in Table 2 below:
TABLE-US-00002 TABLE 2 The effect of water submersion on sample weight loss over 24 hours. Starting weight After 24 hr submersion and shaking Feed .sup.a As-is, g Dry, g Dry, g Weight retained, % Bar type 100.7 54.3 .sup.x 39.3 72 .sup.x Strand type 100.0 56.8 .sup.x 40.1 70 .sup.x Conventional 100.4 94.5 .sup.y 16.5 17 .sup.y .sup.a Each feed type was tested with triplicate samples .sup.x numbers with different superscripts are different (P < 0.01)
[0046] The data shown in Table 2 is (generally) graphically expressed in
[0047] As an alternative or supplement to the water stability test described above, a post-submersion structural integrity test (or alternative water stability test) also provides a measure of the water stability of the aquafeed product. For the purposes of this disclosure, the post-submersion structural integrity test comprises a process wherein an aquafeed is submersed in a (non-agitated i.e. static) room temperature water bath for a specified time (e.g. one hour) and then cut by a 1 mm blade (thickness) to determine a maximum cut force value expressed in g/mm.sup.2 using a force measuring instrument.
[0048] For the purpose of this disclosure, a water-stable aquafeed comprises an aquafeed with a maximum cut force of greater than 10 g/mm.sup.2 after being submersed in water for 1 hour, as measured using the post-submersion structural integrity test described herein.
[0049] With regard to the specifics of the post-submersion structural integrity test used to generate the data presented in Table 3, sinking salmon feed (conventional feed) and three forms of high-moisture aquafeed, as well as fresh salmon were tested. A TA.XT Plus analyzer, with a 50 kg load cell and TA90 platform was used to test the aquafeed products. A triangle-slotted cutting blade (1 mm thickness), also known as Warner Bratzler, was mounted to the machine.
[0050] Each sample (after soaking in water for a selected duration (see Table 3)) was put on the platform with a 2 mm (width) slot. The blade advanced downward, at a speed of 2 mm/second, to cut through the sample. Regardless of the crosscut shapes of samples, only half of the perimeter surface was in contact with the blade edge. This value times 1 mm (blade thickness) was used to calculate the area that contacted the blade. For comparing structural integrity among samples, the maximum force measured was divided by the calculated area, and expressed as g/mm.sup.2 of the contact surface by the blade.
TABLE-US-00003 TABLE 3 Structural integrity (maximum force, g/mm.sup.2, to cut through) after soaking in water of high-moisture feeds and conventional extruded feed. Initial moisture Water soaking time (hours) Feed samples % 0.00 0.16 1.00 2.00 4.00 24.00 Fresh salmon 64.8 29 Conventional 5.8 436 96 6 4 4 3 extruded feed High-moisture feed Strand (dried) 8.3 476 188 36 35 38 34 Strand (as is) 53.6 43 31 27 24 25 27 Pellets (as is) 56.3 41 23 22 20 20 22 Bar (as is) 59.1 39 38 39 36 36 33
[0051] The data shown in Table 3 is (generally) graphically expressed in
[0052] By contrast, the structural integrity of the high-moisture aquafeed remained relatively unchanged over the first 24 hours. Although some softening was observed in the first ten minutes, most of the high-moisture aquafeeds remained within 21 to 35 g/mm2 range (designated by the inventors as the Goldilocks range) for the duration of the test.
[0053] Addtionally, as mentioned above, in a post-production process, the high-moisture aquafeed can be dried for storage and shipping. The characteristics of high-moisture aquafeed that has been dried is shown in Table 3 (and
[0054] The dried high-moisture feed initially has a structural integrity similar to conventional feed. However, as the dried high-moisture feed is rehydrated, the feed begins to exhibit characteristics similar to high-moisture that was not subjected to the drying process. After 24 hours, the dried high-moisture feed exhibits essentially the same structural integrity as the non-dried high-moisture feed.
[0055] The ability to dry and then subsequently rehydrate the feed has important implications for storage, handling, and transportation of the feeds. Pellet Durability Index (PDI) values are determined (using a Holmen Pellet Tester NHP 100). Based on initial testing and observations, the high moisture feed described herein has a PDI value that is comparable to conventional dried feeds.
EXAMPLE
[0056] During proof of concept evaluations, extrusions were performed using a pilot-scale, co-rotating, intermeshing, twin-screw extruder (DNDL-44, Buhler AG, Uzwil, Switzerland) with a smooth barrel and a length/diameter ratio of 32:1 (1422 mm long and 44 mm screws). The barrel of the extruder consists of 6 temperature-controlled sections. Sections 2, 3, 4, and 5 are heated by steam and section 6 is digitally controlled by heated recirculating water (model HY 4003HP, Mokon, Buffalo, N.Y.). The screws are built to have a feed section, mix section, a work section with reversed screw elements, and a final conveying section.
[0057] The extruder further comprised a twin screw gravimetric feeder (KT-20, K-tron Corp, Pitman, N.J.) that was used to feed the raw materials into the extruder at a feeding rate of 10 kg/h. While operating, water at ambient temperature was injected, via an inlet port, into the extruder by a positive displacement pump with 4.5 bar pressure. The inlet port was located on the bottom of the barrel, 0.108 m downstream from the feeding port. The pump was pre-calibrated and adjusted so that the extrudate moisture content would vary from 40 to 80%.
[0058] Optimal screw speeds were varied, dependent on formulation, between 105 and 550 rpm. At the end of the extruder, the tempering unit was attached, with a dimension of 300 mm long and 102 mm in diameter. Each of the insert assembly, regardless of size or shape of the channels, contained 19 mm.sup.2 of open area. The tempering unit was connected to a digitally thermostatically controlled device (model MT 2002 00, Mokon, Buffalo, N.Y.) that maintained the temperature of the tempering unit to 2 C, and optimal temperature varied from 5 to115 C. depending on feed rate formulation, moisture level, and desired product. The finished product was examined for defects and determined to be sufficient for its intended use.
[0059] For the foregoing reasons, it is clear that the method and apparatus described herein provides an innovative method and apparatus for (among other things) manufacturing a water-stable aquatic feed. The current system may be modified in multiple ways and applied in various technological applications. The disclosed method and apparatus may be modified and customized as required by a specific operation or application, and the individual components may be modified and defined, as required, to achieve the desired result.
[0060] Although the materials of construction are not described, they may include a variety of compositions consistent with the function described herein. Such variations are not to be regarded as a departure from the spirit and scope of this disclosure, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.