COLD PRESSING METHOD AND DEVICE IMPLEMENTING SAID METHOD

Abstract

The invention relates to a method for extracting oil from seeds or fruits of oilseed plants, comprising a pressing step and a step of separating the oily and solid fractions, wherein at least a part of the seeds or fruit is moistened prior to the pressing step. The invention also relates to a device for implementing said method.

Claims

1. A method for extracting oil from seeds or fruits of oilseed plants, comprising: one or more steps of cold pressing of the seeds or fruits by means of one or more presses, said seeds or said fruits being conveyed to the one or more presses by a conveyor, and a step of separating the oily fraction and the solid fraction or cake, wherein at least a part of the seeds or fruits is moistened with an aqueous solution prior to the pressing of said seeds or said fruits in order to decrease the temperature of the oil and cakes resulting from the pressing.

2. The method according to claim 1, wherein the aqueous solution is added at a determined flow rate, such that the ratio between said determined flow rate and the flow rate of at least partially moistened seeds or fruits introduced into the press varies from 0.2 to 10%.

3. The method according to claim 1, wherein said seeds or said fruits are moistened by soaking in said aqueous solution for 0 to 30 minutes, such that said moistened seeds or fruits have a moisture content of 4 to 15%.

4. The method according to claim 1, wherein the temperature within the one or more presses is below 100° C.

5. A de-oiled cake of seeds or fruits of oilseed protein plants, obtainable by the method according to claim 1, wherein said cake comprising at most 17% of oil, the percentages being expressed in mass in relation to the total dry mass of the cake.

6. A device for extracting oil from fruits or seeds of oilseed protein plants by a mechanical cold pressing technique, comprising: a press equipped with an inlet and an outlet, the press comprising a worm screw, and a perforated casing forming a cage around the worm screw, the worm screw and the casing being arranged so as to define at least one throttling zone, the throttling zone corresponding to a decrease in the distance between the shaft of the worm screw and the wall of the casing, and a contacting means for bringing an aqueous solution into contact with the fruits or seeds of oilseed protein plants to be pressed, wherein contacting said means being positioned upstream of the inlet of the press.

7. The device according to claim 6, further comprising a guide means, at the inlet of the press, said guide means being positioned between said contacting means and the inlet of the press, said guide means allowing the introduction of the seeds or fruits at the inlet with a fixed flow rate.

8. The device according to claim 6, wherein the contacting means is a nozzle for spraying the aqueous solution, a pipe for adding the aqueous solution drop by drop, or a dipping tank.

9. A device according to claim 6, comprising at least one means for cooling the casing of the press.

10. The device according to claim 6, further comprising at least one means for cooling the screw.

11. The method according to claim 1, wherein the oilseed plants are oilseed protein plants.

12. The method according to claim 1, wherein the ratio between said determined flow rate and the flow rate of at least partially moistened seeds or fruits introduced into the press varies from 0.2 to 5%.

13. The method according to claim 1, wherein the ratio between said determined flow rate and the flow rate of at least partially moistened seeds or fruits introduced into the press varies from 0.5 to 2%.

14. The method according to claim 1, wherein the temperature within the one or more presses is below 85° C.

15. The method according to claim 1, wherein the temperature within the one or more presses is below 75° C.

16. The method according to claim 1, wherein the temperature within the one or more presses is below 65° C.

17. The method according to claim 5, wherein said cake comprises at most 13% of oil.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0130] FIG. 1 illustrates a graph showing the evolution of the temperature in ° C. of the surface of the cake as a function of the speed of rotation of the feed screw (in rpm) with (B.) or without (A.) addition of water at a flow rate of 8 L.Math.h.sup.−1.

[0131] FIG. 2 is a graph showing the impact on the temperature (in ° C. Y axis) along the press (C1a: press inlet to C4c: press exit—effective pressing length of about 3 m) with unmoistened (A) or moistened (B) seeds. The speed is 8 rpm.

[0132] FIG. 3 is a graph showing the percentage of residual oil for the cakes, without addition of water (A) or with addition of water (B) as a function of the speed of the screw in rpm.

[0133] FIG. 4 is a graph showing the variation of seed flow rate without addition of water (A; circles) or with addition of water (B; squares) or of cake flow rate with addition of water (A′; circles) or with addition of water (B′; squares), as a function of the speed of the screw in rpm.

[0134] FIG. 5 is a graph showing the variation of specific intensity of the press without addition of water (A; circles) or with addition of water (B; squares) as a function of the screw speed in rpm.

[0135] FIG. 6 is a schematic representation of a press according to the invention.

[0136] FIG. 7 is a schematic representation of a press according to [FIG. 6] with a guide means.

[0137] FIG. 8 is a schematic representation of a press with a specific contacting means.

[0138] FIG. 9 is a schematic representation of a press according to which the contacting means is a basin.

[0139] FIG. 10 is an alternative schematic representation of a press according to [FIG. 9].

[0140] FIG. 11 is a schematic representation of a device according to the invention combining several presses and several contacting means.

[0141] FIG. 12 is a graph showing the impact of press cooling and water addition on the temperature of the cake at the press outlet. A: cake temperature in ° C., without press cooling or water addition; B: cake temperature in ° C., with press cooling but without water addition; and C: cake temperature in ° C., with press cooling and water addition.

[0142] FIG. 13 is a graph showing the impact of press cooling and water addition on the oil content of the cake at the press outlet. A: residual oil content in %, without press cooling and water addition; B: residual oil content in %, with press cooling but without water addition; and C: residual oil content in %, with press cooling and water addition.

[0143] FIG. 14 is a graph showing the impact of press cooling and water addition on the flow of seeds and cakes. A1: flow of seeds in kg.Math.h.sup.−1 without press cooling or water addition; A2: flow of cake in kg.Math.h.sup.−1 without press cooling or water addition; B1: flow of seeds in kg.Math.h.sup.−1 with press cooling but without water addition; B2: flow of cake in kg.Math.h.sup.−1 with press cooling but without water addition; and B1: flow of seeds in kg.Math.h.sup.−1 with press cooling and water addition and C2: flow of cake in kg.Math.h.sup.−1 with press cooling and water addition.

DESCRIPTION OF ADVANTAGEOUS EMBODIMENTS OF THE DEVICE

[0144] In the various FIGS. 6 to 11, the dotted arrows represent the direction of progression of the seeds or fruits, or cakes, through the device according to the invention.

[0145] Reference is now made to [FIG. 6] which shows a device 1 for extracting oil from fruits or seeds of oilseed protein plants by a mechanical cold pressing technique. This device consists of a press 2 and a means 3 for contacting the seeds or fruits with an aqueous solution.

[0146] The press 2 is formed of a cage 24 covering a worm screw 23, the screw being generally conical in shape with a circular base. The geometry of the screw is such that the space between the lateral edges of the screw and the interior of the cage is more restricted at certain points, defining a throttling zone 200, or several zones depending on the configuration of the screw, at which zone the seeds or fruits introduced into the press are most pressed against the cage 24.

[0147] The press is provided with an inlet 21 through which the seeds or fruits to be pressed are introduced, and where they will be brought into contact with the screw 23. The rotation of the screw 23 makes the seeds or fruits to be pressed progress through the press 2, as far as the outlet 22. As the seeds or fruits progress through the press 2, the oil obtained by the pressing of the seeds or fruits will be eliminated through bars or notches (not shown) provided on the side walls and on the bottom of the cage 24. The residue of pressing, or cake, will be directed and recovered at the outlet 22.

[0148] The device 1 is configured so that the contacting means 3 is positioned upstream of the inlet 21 of the press 2. Therefore, the seeds or fruits that will be introduced into the press 2 through the inlet 21 will have been brought into contact with the aqueous solution.

[0149] With reference to [FIG. 7], a device 1 similar to that of [FIG. 6] is shown, wherein at the inlet 21 of the press 2 there is arranged a guide means 4, serving to optimize the introduction of seeds or fruits into the press 2. This guide means 4 is advantageously a guide means with a screw for controlling the flow of seeds or fruits introduced into the press 2.

[0150] The contacting means 3, in this embodiment, is also upstream of the inlet 21 of the press 2, and upstream of the guide means 4. Thus, the seeds or fruits moistened by the contacting means 3 are introduced into the guide means 4, and are introduced into the press 2 through the inlet 21 for pressing.

[0151] Referring to [FIG. 8], a device 1 according to the invention is now described in which the contacting means 3 is detailed. The contacting means of this embodiment is advantageously provided with a device, or conveyor 5, for conveying the seeds or fruits to be pressed to or towards the contacting means 3. The contacting means 3 is in turn provided with one or more distribution means 31 for releasing the aqueous solution so that it comes into contact with the seeds or fruits conveyed by the conveyor 5. These distribution means 31 can take the form of pipes, nozzles, spray nozzles, or any means allowing the controlled release of the aqueous solution.

[0152] In this embodiment, the seeds or fruits having been moistened by the aqueous solution through the contacting means 3 will then be introduced into the press 2 through the inlet 21, which may or may not be provided with a guide means 4.

[0153] In [FIG. 9], another embodiment of a contacting means 3 is shown. The contacting means 3 is a basin 33 filled with aqueous solution 32 in which the seeds or fruits to be pressed are immersed or bathed. The basin 33 can be provided with a screw or a means of conveying the seeds or fruits thus immersed. A draining means 6 positioned between the basin 33 and the press 2 is also provided, this draining means 6 making it possible to eliminate the excess of aqueous solution having adhered to the fruits or seeds during the soaking in the basin 33.

[0154] In this embodiment, the seeds or fruits having been moistened by the aqueous solution 33 through the contacting means 3 will then be introduced into the press 2 through the inlet 21, which may or may not be provided with a guide means 4.

[0155] [FIG. 10] shows an alternative arrangement of the device 1 shown in [FIG. 9]. In this embodiment, the draining means and the basin 33 containing the aqueous solution 32 are physically separated. The seeds or fruits having remained in the basin 33 to be brought into contact with the aqueous solution 32 will be transferred into or onto the draining means by any means easily usable by the person skilled in the art (elevator, basket, or simply by tipping the contents of the basin 33 into or onto the draining means 6).

[0156] In this embodiment, the seeds or fruits having been moistened by the aqueous solution 33 through the contacting means 3 will then be introduced into the press 2 through the inlet 21, which may or may not be provided with a guide means 4.

[0157] In advantageous embodiments, the device 1 may comprise more than one press 1 and more than one contacting means 3. This is, for example, illustrated in [FIG. 11]. The device 1 is provided with a first contacting means 3, followed by a press 2. At the exit of the first press, the cake is then placed back on a conveyor 5, advancing it to a second contacting means 3. After this second moistening, the moistened cake is introduced into a second press 2, for a second pressing. This is a duplication of the arrangement shown in [FIG. 8].

[0158] It is of course understood that duplications of the arrangements shown in FIGS. 9 and 10 are also covered by the present invention.

[0159] Also envisaged within the scope of the present invention are devices 1 combining the arrangements shown in FIGS. 8, 9 and 10. For example, covered by the present invention is a device comprising a pair of contacting means 3 and press 2 as shown in [FIG. 8], arranged so that the cake leaving the press is taken over by a second pair of contacting means 3 and press 2 as shown in [FIG. 9] or 10. The reverse is also possible.

[0160] In other words, the arrangements in FIGS. 8, 9 and 10 can be combined with each other.

EXAMPLES

Example 1

[0161] The objective of the tests carried out was to reduce the heating of cakes obtained during the pressing of oilseed plant seeds in a screw press, used for oil extraction.

[0162] The inventors conducted tests by spraying tap water on a flow of seeds before introducing it into a screw press.

[0163] Tests were carried out in a trituration unit working in cold pressing with a Reinartz AP15 press. This is an industrial press model, with a maximum capacity of 1 T/h, equipped with a frequency converter making it possible to adjust its rotation speed from 5 to 10 rpm.

[0164] The feeding of the press is gravitational and ensured by a horizontal screw conveyor, also on a frequency variator making it possible to adjust the flow of seeds introduced in the press.

[0165] In contrast to the standard Reinartz model, this press was equipped with a water cooling system in the shaft and in the last two cage sections (sections C3 and C4), as well as a screw arrangement optimized for spring rapeseed.

[0166] A water spray system was installed above the penultimate section of the feed screw. In this test, the spray system is a flexible garden hose, connected to the running water system, and a faucet. The faucet was opened very slightly, so that only a very small flow of water was added to the seeds. In this way, the flow was a small trickle of water that resulted in a very heterogeneous distribution, with some seeds heavily moistened and others remaining dry.

[0167] Water spray pressing tests were performed on spring rapeseed from Latvia, cleaned but not pretreated (no flattening or cooking).

[0168] The operating performances obtained with and without the addition of water to the feed were compared, for identical operating conditions. For this purpose, in both cases, the press was operated with a full screw (with cooling water circulation at 5° C. in the shaft and the last two cage sections (C3 and C4)), at two different screw rotation speeds (8 and 10 rpm).

[0169] 1—Control 1: diameter of die holes 7 mm/cooling of cage and shaft by water at 5° C./No addition of water.

[0170] Press shaft speed 80% of nominal (8 rpm)/screw feeding speed 27% (corresponds to 449 kg/of cake or 830 kg/h of seeds approximately)

[0171] 1—Control 2: diameter of die holes 7 mm/cooling of cage and shaft by water at 5° C./No addition of water.

[0172] Press shaft speed 100% of nominal (10 rpm)/screw feeding speed 30% (corresponds to 520 kg/of cake or 920 kg/h of seeds approximately)

[0173] 2—Test no 1: diameter of die holes 7 mm/cooling of cage and shaft by water at 5° C./addition of water in screw feed 8 L/h,

[0174] Press shaft speed 80% of nominal (8 rpm)/screw feeding speed 27% (corresponds to 438 kg/of cake or 830 kg/h of seeds approximately)

[0175] 3—Test no 2: diameter of die holes 7 mm/cooling of cage and shaft by water at 5° C./addition of water in screw feed 8 L/h

[0176] Press shaft speed 100% of nominal (10 rpm)/screw feeding speed 30% (corresponds to 520 kg/of cake or 920 kg/h of seeds approximately)

[0177] The temperature results without watering (A) and with watering at 8 L/h (B) are shown in [FIG. 1].

[0178] All of these results show that the addition of water at the screw feed significantly reduces the temperature of the cakes.

[0179] There is a significant decrease in the final temperature of the cake after pressing, with a drop of 7° C. at 8 rpm and 10° C. at 10 rpm.

[0180] Next, the inventors established the temperature profile along the press cage without (A) or with (B) addition of water to the seeds prior to entering the press.

[0181] The results are shown in [FIG. 2].

[0182] These results show that with and without the addition of water, the temperature variation follows a very similar evolution, but actually shows a slight decrease in the case of the addition of water, for almost all the measuring points. This confirms the reduction of friction, desired by the inventors.

[0183] Next, the inventors tested whether the addition of water to the seeds prior to pressing had an effect on oil production, and thus cake de-oiling. The inventors compared the oil content of cakes produced by pressing without (A) or with (B) the addition of water, at a speed of 8 or 10 rpm.

[0184] The oil content is measured according to the method defined in the international standard ISO 734 in its February 2016 version.

[0185] The results are shown in [FIG. 3].

[0186] While the residual oil content obtained without the addition of water is generally around 10% by mass in relation to the dry mass of the cake, it would seem that in the case where water is added, this addition induces a slight decrease in the de-oiling performance and thus an increase in the residual oil content around 11%.

[0187] Ultimately, an important characteristic to determine was whether water addition impacted seed flow rates (A without water addition and B with water addition) and cake flow rates (A′ without water addition and B′ with water addition) during pressing, as well as specific press intensity (A without water addition and B with water addition).

[0188] The results are shown in [FIG. 4] for the flow rates and in [FIG. 5] for the intensity.

[0189] They reveal that the addition of water has no influence on the flow rates of treated seeds and cake produced, but induces a slight decrease in the specific intensity of the press, related to the decrease in de-oiling mentioned above.

[0190] A drop in specific intensity was even observed during the tests, during the adjustment of the water flow rate, showing that an excessive flow rate can reduce the stresses in the press, i.e. the friction but also the de-oiling performance. Therefore, the inventors set the water flow rate to be added as mentioned above.

Example 2

[0191] Using the device described in the previous example, the inventors then wanted to compare the efficiency of cooling the press by water circulation in its shaft and cage and of cooling induced by moistening of the pressed seeds.

[0192] Pressing tests were carried out on spring rapeseed from Latvia, cleaned but not pre-treated (no flattening or cooking).

[0193] The operating performances obtained with and without cooling of the press and with and without addition of water to the feed were compared, for identical operating conditions. For this purpose, for the 3 modalities, the press was operated with a full screw, at a rotation speed of 8 rpm.

[0194] 1—Control 1 (A): diameter of die holes 7 mm/No cooling of shaft and cage/No addition of water.

[0195] Press shaft speed 80% of nominal (8 rpm)/screw feeding speed 27% (corresponds to 438 kg/of cake or 830 kg/h of seeds approximately)

[0196] 1—Control 2 (B): diameter of die holes 7 mm/cooling of cage and shaft by water at 5° C./No addition of water.

[0197] Press shaft speed 80% of nominal (8 rpm)/screw feeding speed 27% (corresponds to 449 kg/of cake or 830 kg/h of seeds approximately)

[0198] 2—Test no 1 (C): diameter of die holes 7 mm/cooling of cage and shaft by water at 5° C./addition of water in screw feeding 8 L/h.

[0199] Press shaft speed 80% of nominal (8 rpm)/screw feeding speed 27% (corresponds to 445 kg/of cake or 830 kg/h of seeds approximately)

[0200] The results for temperature without cooling and without watering (A) and with cooling and without watering (B) and with cooling and with watering at 8 L/h (C) are shown in [FIG. 12].

[0201] These results show that the addition of water at the screw feed significantly improves the temperature drop of the cakes linked to the cooling of the press by water circulation in its shaft and cage.

[0202] A decrease is observed in the final temperature of the cake, after pressing, of 3° C. (temperature difference between A and B; [FIG. 12]) by the effect of the cooling of the press and of 7° C. (temperature difference between B and C; [FIG. 12]) by the effect of the addition of water.

[0203] Next, the inventors tested whether the cooling of the press and the addition of water to the seeds before pressing had an effect on oil production, and thus on the de-oiling of the cakes. The inventors therefore compared the oil content of cakes from pressing without cooling and without watering (A) and with cooling and without watering (B) and with cooling and with watering at 8 L/h (C).

[0204] The oil content is measured according to the method defined in the international standard ISO 734 in its February 2016 version.

[0205] The results are shown in [FIG. 13].

[0206] It can be seen that, even if the addition of water affects the de-oiling of the cakes, the oil content after pressing remains below 12%, which is a perfectly acceptable amount.

[0207] Ultimately, an important characteristic to determine was whether press cooling and water addition impacted seed and cake flow rates during pressing, as well as the specific intensity of the press.

[0208] The results are shown in [FIG. 14] for the flow rates.

[0209] They reveal that neither the cooling of the press nor the addition of water has any influence on the flow rates of treated seeds and cake produced.