Native collagen extraction from fish scales

Abstract

The invention relates to a device (2) for mechanically extracting native collagen from dried fish scales, comprising: - a tank (4) sized to receive a batch of fish scales, - an element (8) for closing the tank (4) placed at the top of the tank (4), - rotary motorized blades (14, 14') arranged in the tank (4) and sized to defibrate the fish scales, and - mechanical separation means (22) for separating the native collagen fibers from other parts of the fish scales produced by the defibration.

Description

extraction of native collagen from fish scales

[0001] The invention relates to the extraction of native collagen from fish scales.

[0002] The fishing and aquaculture industries produce large quantities of waste, of which fish scales are one of the least valued by-products. Several hundred thousand tons of fish scales are generated each year by the fishing and aquaculture industries. Today, fish scales are very undervalued by-products. However, the collagen and hydroxyapatite that make up the scales are molecules of interest with high added value.

[0003] Collagen is the most widespread biopolymer in the animal world. It is a polypeptide chain composed of amino acids, found in particular in skin and bones. Porcine, ovine, or marine skins and bones are the most common sources of collagen and its hydrolyzed form, gelatin. These components are very useful for the food industry, where they are used as a binder and texturizing agent. Cosmetics and nutraceuticals are also important markets, particularly due to the biocompatible nature of collagen. This is also true for the biomedical industry, which is also experiencing a growing demand for native collagen, albeit on a smaller scale. Hydroxyapatite is a biomineral also present in the mineralized structures of the animal world. It has interesting properties, particularly for the nutraceutical, biomedical, and cosmetic sectors.

[0004] Fish scales are still rarely used for native collagen extraction, with fish skin being preferred. The conventional process for extracting collagen from fish scales is directly inspired by the processes for extracting collagen from skin. Collagen from fish scales is therefore currently mainly extracted chemically using acidic and basic solutions to break down the natural material and isolate the targeted molecules.

[0005] The conventional extraction technique consists of pretreatment with a strong basic solution such as sodium hydroxide, followed by treatment with acetic acid or hydrochloric acid. EDTA (ethylenediaminetetraacetic acid), a chelating agent that complexes heavy metals, is often used to demineralize the scales before the extraction step. Standard laboratory extraction steps for native collagen are: sodium hydroxide pretreatment, scale demineralization with EDTA, collagen extraction at 4°C using acetic acid, centrifugation, salting out (or salt precipitation in French), to purify the collagen, dialysis, and drying in a freeze dryer.

[0006] An enzymatic hydrolysis step can be added to, or replace, the acetic acid extraction phase to improve yield.

[0007] This extraction method has several drawbacks. First, it does not follow the precepts of green chemistry with the use of numerous chemical agents. In addition, the various hydrolyses are difficult to control, which can lead to denaturation of the extracted molecules of interest. The collagen chains are cut randomly, making the nature of the peptides produced difficult to predict and control.

[0008] Furthermore, this extraction takes several days and has a limited yield. Finally, it consumes a large amount of water, and the use of a freeze dryer at the end of extraction consumes a significant amount of energy (around 1500 to 2500 kWh per ton of evaporated water). Extraction is therefore expensive and energy-intensive.

[0009] The invention therefore aims to provide a device for extracting native collagen from fish scales that is faster and less energy-intensive than the methods of the prior art. The invention also makes it possible to obtain a higher yield than the prior art and a high purity rate. Finally, the invention makes it possible to obtain native collagen fibers that retain a natural structure.

[0010] To this end, the invention relates to a device for mechanically extracting native collagen from dried fish scales comprising: a tank sized to receive a batch of fish scales, a tank closing member placed at the top of the tank, rotating motorized blades arranged in the tank and sized to defiberize the fish scales, and means for mechanically separating the native collagen fibers from other parts of the fish scales resulting from the defibering.

[0011] Thus, the extraction device eliminates the need for chemicals and collagen solubilization, which prevents denaturing the extracted collagen fibers. Such an extraction allows, in a time varying between 10 seconds and 3 minutes, to obtain an optimal level of purity of native collagen fibers comprising only an impurity rate varying between 0.3% and 20%. Finally, the extraction carried out entirely mechanically considerably limits the use of water and energy consumption.

[0012] According to other optional features of the extraction device taken alone or in combination: the extraction device comprises means for cleaning and drying the fish scales before placing them in the tank. The means for preparing the fish scales are therefore integrated into the device; the means for cleaning the fish scales comprise at least one clear water bath; the means for drying the fish scales comprise at least one support grid and at least one hot air blower; the drying means can be powered by a renewable energy source and / or waste energy. the tank is made from an alloy of greater hardness than hydroxyapatite. This limits the pollution of the native collagen fibers by steel particles; the tank is made at least partly of stainless steel; the tank is arranged on an axis so as to be able to tilt.This makes it easier to empty the tank; the extraction device includes means for adjusting the height of the closing member on the tank.This makes it possible to adjust the volume of the tank thanks to the adjustable placement of the closing member; the means for adjusting the height of the closing member on the tank comprise adjustment screws and / or notched adjustment elements; the motorized blades are carried by an axle itself connected to a motor; at least one motorized blade is formed by a metal bar, for example of rectangular cross-section, comprising a perforated central portion connected to the axle and at least one terminal portion forming an angle of between 30° and 70° with the central portion; at least one motorized blade is formed by a metal bar, for example of rectangular cross-section, flat; the motor is sized to allow rotation of the motorized blades between 5,000 and 30,000 revolutions per minute; the motor is coupled to a speed variator.The rotation speed of the motorized blades is thus adjusted according to the type and quantity of scales present in the tank; the shaft is threaded. This allows easy attachment of the motorized blades to the shaft; the shaft is made of stainless steel; at least one spacer is arranged on the shaft between two successive motorized blades; the means for mechanically separating the native collagen fibers from other parts of the fish scales resulting from the defibering comprise at least one system for suctioning the contents of the tank placed opposite an opening of the tank, the tank comprising means arranged to prevent the passage of native collagen and to allow the passage of hydroxyapatite and impurities. This provides a possibility of separating the native collagen from the other products resulting from the defibering concomitantly with said defibering of the fish scales; the extraction device comprises a member for measuring the temperature inside the tank.This makes it possible to identify any heating of the interior of the tank that could denature the collagen fibers; the member for measuring the temperature inside the tank is coupled to a member for lowering the temperature inside the tank. This makes it possible to avoid any heating of the interior of the tank that could denature the collagen fibers; the member for lowering the temperature inside the tank comprises at least one element chosen from: a system for stopping the motorized blades, a system for limiting the rotation speed of the motorized blades or a device for injecting at least one cooling agent, for example liquid nitrogen.

[0013] The invention also relates to a method for mechanically extracting native collagen from fish scales using an extraction device according to the invention, the steps of the method being as follows: cleaning and drying the scales, inserting the scales into the tank, mechanically defibering the scales by rotating the motorized blades, and mechanically separating the native collagen fibers from other parts of the fish scales resulting from the defibering.

[0014] According to other optional characteristics of the extraction process taken alone or in combination: the cleaning is chosen from water cleaning or enzymatic cleaning; the height of the closing member relative to the tank is chosen according to the volume of fish scales in the tank; the tank is inclined during the step of mechanical defibration of the scales by rotating the motorized blades; the motorized blades are rotated at a speed of between 5,000 and 30,000 revolutions per minute, preferably between 15,000 and 25,000 revolutions per minute; the motorized blades are rotated for a period of between 10 seconds and 3 minutes; the speed of rotation of the motorized blades varies during the step of mechanical defibration of the scales by rotating the motorized blades;a suction system sucks up the contents of the tank during the step of mechanical defibration of the scales by rotating the blades, the tank comprising means preventing the exit of native collagen fibers and allowing the exit of hydroxyapatite and impurities; the temperature inside the tank is measured during the step of mechanical defibration of the scales by rotating the motorized blades; the temperature inside the tank is lowered during the step of mechanical defibration of the scales by rotating the motorized blades; and the temperature inside the tank is lowered during the step of mechanical defibration of the scales by rotating the motorized blades by reducing the rotation speed of the motorized blades, by stopping the rotation of the motorized blades, or by injecting at least one cooling agent, for example liquid nitrogen.; Brief description of the figures

[0015] The invention will be better understood on reading the following description, given solely by way of example and with reference to the appended drawings in which:

[0016] is a sectional view of a device for mechanically extracting native collagen from fish scales according to one embodiment of the invention, and

[0017] is a schematic representation of a method for mechanically extracting native collagen from fish scales according to one embodiment of the invention. Detailed description

[0018] Reference is now made to the illustrating a device for mechanical extraction 2 of native collagen from dried fish scales. Native collagen is understood to mean undenatured collagen, having retained its triple helix conformation. "Mechanical extraction" is understood to mean extraction of native collagen not requiring the use of chemicals such as those mentioned above, for example by successive baths.

[0019] Fish scales are typically washed and then dried before the mechanical extraction phase of native collagen. To do this, it is possible for the extraction device 2 to comprise means for cleaning and drying the fish scales before mechanical extraction of the native collagen. Alternatively, the extraction device may receive fish scales that have already been washed and dried.

[0020] The means for cleaning fish scales may include at least a bath of clear water, preferably slightly acidic, to rinse the fish scales. It may also be an enzymatic washing cleaning.

[0021] Regarding the means for drying fish scales, they can be formed by at least one support grid and at least one hot air blower. Advantageously, the drying means are powered by a renewable energy source and / or waste energy.

[0022] The extraction device 2 comprises a tank 4 intended to receive the dried fish scales. The latter comprises at least one opening for introducing fish scales.

[0023] Tank 4 is preferably made from an alloy with a harderness greater than that of hydroxyapatite. This limits the contamination of the native collagen fibers by steel particles. For example, tank 4 may be made at least partly from stainless steel (this also makes it easier to clean tank 4).

[0024] The tank 4 is arranged on an axis 6 so that it can tilt. This tilting possibility makes it easier to empty the tank 4. In addition, an inclination of the tank 4 also allows separation of the native collagen from the other components derived from the fish scales. To allow such tilting, the tank 4 is positioned on a tilting axis, facilitating the separation of the phases by gravity during the process.

[0025] The volume of the tank 4 can be adjustable, in particular depending on the volume of fish scales introduced into the tank 4. Indeed, it is preferable to limit the movement of the fish scales in the tank 4 in order to facilitate the defibration by shearing of the fish scales and therefore the extraction of native collagen. To do this, it is possible to provide means for adjusting the height of the closing member 8 on the tank 4. These adjustment means can be formed by adjustment screws 10 as can be seen in the. The closing member can therefore adopt a U-shaped section (it can for example be a cylinder having a wall at one of its ends if the tank has a circular opening). Each adjustment screw 10 collaborates with two supports 12 crossed by threaded orifices, one carried by the tank 4 and the other by the closing member 8.The relative screwing of the adjustment screws 10 on the supports 12 carried by the closing member 8 with respect to that of the adjustment screws 10 on the supports carried by the tank 4 makes it possible to adjust the height of the closing member 8 of the tank 4 on the latter. Alternatively to the use of adjustment screws 10, it is possible to use a notched adjustment element, for example using pairs of notched rods placed respectively on the tank 4 and on the closing member 8.

[0026] The extraction device 2 also comprises rotating motorized blades 14 and 14', arranged in the tank 4 and sized to defiberize the fish scales. The latter act like flails when they are rotated, which allows the defibering of the fish scales present in the tank 4.

[0027] The motorized blades 14 and 14' are rotated by the axis 6, connected directly or indirectly to a motor 16. The motorized blades 14 and 14' are removably mounted on the axis 6. This allows easy maintenance and modularity of the extraction device 2 with replacement of motorized blades of a given shape by other motorized blades of another shape. Alternatively, the motorized blades could be part of a rotating block made from a single piece.

[0028] As shown in the, at least one motorized blade, here the motorized blade 14 may be formed by a metal bar, for example of rectangular cross section, comprising a central portion 18 preferably perforated (i.e. comprising a through-orifice) connected to the axis 6 and at least one terminal portion, here two terminal portions 18', forming an angle of between 30° and 70° with the central portion (the angle is approximately equal to 45° on the). Alternatively or in addition, at least one motorized blade, here the motorized blade 14', may be flat and preferably also perforated.

[0029] Advantageously, the shape of at least part of the motorized blades makes it possible to avoid stagnation of the fish scales in the tank 4. In the example illustrated, the flat motorized blade 14' is placed at the bottom of the tank 4 to avoid such stagnation.

[0030] As explained above, the axis 6 is connected to a motor 16. This motor 16 can be sized to allow rotation of the motorized blades 14 and 14' between 5,000 and 30,000 revolutions per minute, preferably between 15,000 and 25,000 revolutions per minute, this speed range being the most suitable. Generally, the rotation speed of the motorized blades 14 and 14' is adapted according to the type and quantity of scales in the tank 4.

[0031] The motor is advantageously coupled to a speed variator. This makes it possible to adjust the rotation speed from one defibering step to another for different batches of scales, or to vary the rotation speed of the motorized blades 14 and 14' during the same defibering step if this is advantageous.

[0032] The shaft 6 is preferably made of stainless steel, for the same reasons as the tank 4. It is preferably threaded, as is the case on the. This can allow the motorized blades 14 and 14' to be screwed if the through-hole of the motorized blades 14 and 14' is threaded. In this case, tightening can be carried out using a tightening bolt 20.

[0033] At least one spacer can be placed between the successive motorized blades 14 and 14'. The distance separating the motorized blades 14 and 14' can then be adjusted and thus adapted to the type and volume of scales present in the tank 4.

[0034] The extraction device further comprises, and as explained above, a closing member 8 of the tank 4 placed at the top of the tank 4. This may for example be a solid plate.

[0035] The extraction device 2 further comprises means for mechanically separating the native collagen fibers from other parts of the fish scales resulting from the defibering.

[0036] In the example illustrated in , these mechanical separation means comprise at least one suction system 22 placed opposite an opening for introducing fish scales from the tank 4. This suction system 22 is sized and placed so as to suck up the contents of the tank 4. In this case, the tank 4 comprises means arranged to prevent the passage of native collagen and to allow the passage of hydroxyapatite and impurities. The tank 4 may for example comprise openings allowing the extraction from the tank 4 of certain products resulting from the defibering of the fish scales, while preventing the exit from the tank 4 of other products resulting from this defibering. The other components resulting from the defibering, such as hydroxyapatite, are then removed from the tank 4, concomitantly with the defibering by the motorized blades 14, in order to retain only the purest possible native collagen in the tank 4.

[0037] Advantageously, the extraction device 2 may comprise a member for measuring the temperature inside the tank 4, for example a temperature sensor arranged in the tank 4. This makes it possible to identify any heating of the inside of the tank 4 which could denature the collagen fibers. Indeed, to avoid any risk of denaturation of the native collagen, it is preferable to keep the temperature inside the tank below 60°C.

[0038] With this same temperature control in mind, it is possible to couple the temperature measuring member inside the tank 4 to a member for lowering the temperature inside the tank 4. This makes it possible to avoid any possible heating of the inside of the tank which could denature the collagen fibers. Advantageously, the member for lowering the temperature inside the tank 4 comprises at least one element chosen from: a system for stopping the rotation of the motorized blades 14 and 14', a system for limiting the rotation speed of the motorized blades 14 and 14', or a device for injecting at least one cooling agent, for example liquid nitrogen, for example all around the tank.

[0039] With regard to the method of mechanical extraction of native collagen from fish scales using an extraction device according to the invention, the first step 24 may be cleaning (with clear water or enzymatic cleaning) and drying of the fish scales using means described above.

[0040] Following this step, a volume of fish scales is placed inside the tank 4 (step 26). It is then possible to adjust the height of the closing member 8 on the tank 4 as explained above, in particular as a function of the volume of fish scales introduced into the tank 4.

[0041] A step 28 of defibering the fish scales by rotating the motorized blades 14 and 14' is implemented. As explained above, the motorized blades 14 and 14' can be rotated at a speed of between 5,000 and 30,000 revolutions per minute, preferably between 15,000 and 25,000 revolutions per minute, for a period preferably varying from 10 seconds to 3 minutes. The rotation speed of the motorized blades can vary during step 28 of defibering the fish scales.

[0042] During this step 28 of defibering the fish scales, the tank 4 can be tilted to allow the mechanical separation of the native collagen fibers from other elements resulting from the defibering.

[0043] As explained above and illustrated in the, the step 30 of mechanical separation of the native collagen fibers from other elements resulting from the defibering can be done concomitantly with that of defibering the fish scales. It can be carried out by the suction system 22 described above. Alternatively, it is possible to mechanically separate the collagen from the other elements resulting from the defibering after defibering, for example by recovering the defibered scales and then passing them over a vibrating sieve.

[0044] It is possible to provide a step 32 for measuring the temperature inside the tank 4, for the reasons mentioned above, during the step of defibering the fish scales. In the event of an increase in the temperature in the tank 4 above a threshold value, a step 34 for lowering the temperature inside the tank 4 can be implemented by reducing the rotation speed of the motorized blades 14 and 14', by stopping the rotation of the motorized blades 14 and 14', or by injecting at least one cooling agent such as liquid nitrogen.

[0045] Finally, it is possible to provide a step 36 of micronization of the extracted native collagen fibers, for example in a rotor mill, in order to increase the solubility of the collagen in the acid.

[0046] According to an exemplary implementation of the invention, 20 grams of dry scales (residual moisture content around 11%) of tilapia (Oreochromisniloticus) are placed in the stainless steel tank 4 with a diameter of 14 centimeters. Two flat and straight motorized blades 14' made of stainless steel, with a length equal to 13.5 cm, and a motorized blade 14 of the shape described above (with a length of 6 centimeters and a height of 2 centimeters) are positioned one after the other on the axis 6, the whole being tightened and secured by a tightening bolt 20.

[0047] With the adjustment screws 10, a closing member 8 is positioned so that the height of the chamber defined by the tank 4 and the closing member 8 is 7 centimeters.

[0048] A suction system 22 is installed at tank 4 to separate the products resulting from the defibering. An air inlet into tank 4 is provided to avoid creating a vacuum. The speed of the motorized blades is set at 28,000 rotations per minute, and step 28 of defibering the fish scales is 1 minute and 30 seconds. After defibering the fish scales and mechanical separation of the native collagen fibers from other elements resulting from the defibering, 6 grams of pure native collagen (the impurity rate is less than 2%) are recovered in fibrous form.

[0049] The physicochemical analyses carried out demonstrate that the properties of this collagen are those of a native collagen having retained its triple helix conformation. This collagen can then be solubilized in an organic or inorganic acid (conventionally acetic acid) or used directly for the formation of biofilms or biomaterials, among others. A suction bag of the suction system 22 contains 14 grams of residue, mainly composed of mineral, with a hydroxyapatite content greater than 60%. The operation can then be repeated instantly by reloading the tank 4 with fish scales. List of references

[0050] 2: extraction device4: tank

[0051] 6: axis

[0052] 8: closing organ

[0053] 10: adjustment screw

[0054] 12: support

[0055] 14, 14': rotating blades

[0056] 16: engine

[0057] 18: central portion

[0058] 18': final portions

[0059] 20: clamping bolt

[0060] 22: suction system

[0061] 24: Cleaning and drying fish scales

[0062] 26: Inserting the fish scales into the tank

[0063] 28: defibering fish scales

[0064] 30: mechanical separation of native collagen fibers from other elements resulting from defibration

[0065] 32: measurement of the temperature inside the tank

[0066] 34: lowering the temperature inside the tank

[0067] 36: micronization of native collagen fibers

Claims

Device (2) for mechanical extraction of native collagen from dried fish scales comprising: a tank (4) sized to receive a batch of fish scales, a closing member (8) of the tank (4) placed at the top of the tank (4), rotating motorized blades (14, 14') arranged in the tank (4) and sized to defiberize the fish scales, and means (22) for mechanical separation of the native collagen fibers from other parts of the fish scales resulting from the defibering. Extraction device (2) according to claim 1, comprising means for cleaning and drying the fish scales before placing them in the tank (4). Extraction device (2) according to any one of the preceding claims, in which the tank (4) is made from an alloy of hardness greater than that of hydroxyapatite. Extraction device (2) according to any one of the preceding claims, comprising means (10, 12) for adjusting the height of the closing member (8) on the tank (4). Extraction device (2) according to any one of the preceding claims, comprising an axis (6) carrying the motorized blades and connected to a motor (16) coupled to a speed variator. Extraction device (2) according to any one of the preceding claims, in which the means for mechanically separating the native collagen fibers from other parts of the fish scales resulting from the defibration comprise at least one suction system (22) for the contents of the tank (4) placed opposite an opening of the tank (4), the tank (4) comprising means arranged to prevent the passage of native collagen and to allow the passage of hydroxyapatite and impurities. Extraction device (2) according to any one of the preceding claims, comprising a member for measuring the temperature inside the tank (4). Extraction device (2) according to the preceding claim, in which the member for measuring the temperature inside the tank (4) is coupled to a member for lowering the temperature inside the tank (4). A method for mechanically extracting native collagen from fish scales using an extraction device according to any one of the preceding claims, the steps of the method being as follows: cleaning and drying (24) the scales, inserting (26) scales into the tank, mechanically defibering (28) the scales by rotating the blades, and mechanically separating (30) the native collagen fibers from other parts of the fish scales resulting from the defibering. Extraction method according to claim 9, in which the height of the closing member (8) relative to the tank (4) is chosen as a function of the volume of fish scales in the tank. Extraction method according to any one of claims 9 and 10, in which a suction system (22) sucks up the contents of the tank (4) during the step (28) of mechanical defibration of the scales by rotating the motorized blades (14, 14'), the tank (4) comprising means preventing the exit of native collagen fibers and allowing the exit of hydroxyapatite and impurities. Extraction method according to any one of claims 9 to 11, in which the temperature inside the tank (4) is measured during the step (28) of mechanical defibration of the scales by rotating the motorized blades (14, 14'). Extraction method according to claim 12, in which the temperature inside the tank (4) is lowered during the step (28) of mechanical defibration of the scales by rotating the blades.

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