Method for a combined cell digestion and extraction of oil-containing seeds

Abstract

The invention relates to a method of combined cell digestion and extraction of oil-containing seeds having an oil content of >30% by mass, wherein production of a slurry from the oilseeds and ethanol is followed by a combination cell digestion with a subsequent ethanolic extraction, wherein the smaller portion of the oil of the oilseed and the alcohol-soluble constituents present therein are dissolved in the ethanol in accordance with the dissolution capacity of the ethanol for the oil and the alcohol-soluble constituents, a greater portion of the oil is displaced from the seed cells by the ethanol, forming a free oil phase in the ethanol. The free oil phase is removed and, according to the invention, has semi-raffinate quality, reducing the complexity of refining as an advantage of the method of the invention.

Claims

1. A method for a combined digestion and extraction of oil-containing, seeds, comprising the following steps: producing a mash from seed cells of oilseed and ethanol as solvent, said oilseed having oil content of 30 mass%, digesting the seed cells of the oilseed in ethanol by mechanical means to an average particle size of 50 m, followed by an ethanol extraction, wherein during said ethanol extraction a smaller portion of oil in the seed cells of the oilseed and alcohol soluble constituents dissolve into the ethanol to form a liquid miscella phase, and a larger portion of the oil from the seed cells is being displaced by ethanol to form a free oil phase within the ethanol; separating the free oil phase and separating the oil and alcohol soluble constituents from the miscella phase, wherein the free oil phase includes a portion of phosphatides of 0.1%, and a portion of free fatty acids of 0.5%, separating a remaining extraction residue after extraction and removal of residual ethanol from the extraction residue in vacuum at a temperature of <90 C. and a pressure of <500 mbar, wherein cell digestion and extraction is carried out in a defined mass-ratio of oilseed to ethanol of 1:3 to 1:8 wherein the free oil is present as a separate liquid phase and obtained without distillation, and wherein the extraction is carried out at below the atmospheric boiling temperature of the ethanol.

2. The method according to claim 1, prior to producing the mash from oilseed arid ethanol and the oilseed is dried to a water content of 5%.

3. The method according to claim 1, wherein the ethanol used as an alcoholic solvent has a water content of maximally 5% by weight.

4. The method according to claim 1, wherein the method is carried out as a continuous or, quasi continuous, multistep extraction method configured for parallel flow or reverse flow.

5. The method according to claim 1, wherein the cell digestion is carried out by means of a rotor-stator system or by means of a high pressure homogenizer.

6. The method according to claim 1, further comprising a filtration step wherein the liquid miscella phase and free oil phase are separated from particles after the cell digestion and ethanol extraction, wherein the filtration is carried out by means of pressure filtration, screen filtration, or by a centrifuge or, decanter.

7. The method according to claim 1, applying ultra sound and agitators to accelerate the cell digestion and subsequent separation of the liquid phase.

8. The method according to claim 1, wherein the oilseeds used are selected from rape, flax, sunflower and other oilseeds having an oil content of 30 mass%.

9. The method according to claim 1, wherein after concluded fractionation, the miscella is returned to the extraction residue to thereby realize a repeated utilization of the ethanol for further processing of cell digestion and extraction.

10. The method according to claim 1, further comprising the step of recovering the ethanol from the separation of the dissolved oil, the further constituents from the miscella and from the extraction mix and using the recovered ethanol for additional extraction steps.

11. The method according to claim 1, wherein substantially completely hulled oilseeds as well as non-hulled seeds are used.

12. The method according to claim 1, wherein oilseeds are utilized in an integrated oil production course.

13. The method according to claim 1, wherein the free oil phase includes a portion of phosphatides of 0.025%.

14. The method according to claim 1, wherein the free oil phase includes a portion of free fatty acids of 0.3%.

15. The method according to claim 1, wherein the mass ratio oilseeds to ethanol is 1:5.

16. The method of claim 1, wherein separation of the remaining extraction residue after extraction and removal of residual ethanol from the extraction residue in vacuum is carried out at a temperature of between 50 and 90 C.

17. The method according to claim 1, wherein after concluding the extraction, an alcohol-moist extraction residue is obtained which is mechanically pressed and thereafter dried under gentle condition under vacuum.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:

(2) FIG. 1 shows a schematic illustration of the method steps of the present invention in co-current flowexemplary in a three-step extraction,

(3) FIG. 2 shows a schematic illustration of the method steps of the present invention in an reverse current flow exemplary in a three-step extraction, and

(4) FIG. 3 shows a schematic illustration of an extraction arrangement.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(5) In a first embodiment, with reference to FIG. 1 the method of the co-current is shown in an example of rapeseed in a three step extraction.

(6) From the oilseed, which for example was previously dried and crushed, together with the ethanol, a mash is produced followed by the mechanical cell digestion, for example by means of a rotor-stator system. Thereafter, the solvent and displacement extraction follows, during which a part of the oil is dissolved in the alcoholic phase and when the solubility capacity of the alcoholic solvent is surpassed (displacement) the oil collects as droplets in the alcoholic solvent. After that, a separation of miscella and free oil phase follows. After separation of the free oil phase, the miscella can be reused directly for additional displacement steps. Furthermore, at the solvent recovery which is carried out by means of an evaporator, separation of the dissolved oil from the other constituents that are bottom products (distillation residue) takes place. This makes a repeated utilization of the alcoholic solvent (distillate) possible.

(7) The extraction and displacement method results in free and dissolved oils, alcohol soluble constituents such as phospholipids, phenolic compounds or glucosinolates, and a solid matter phase (rape extraction meal), which can be considered as high quality feedstuff or as starting product for protein extraction.

(8) Alternatively, in a further embodiment, FIG. 2 illustrates the afore-described embodiment in the form of an inverse flow process. There, the mash is produced from the starting product and the miscella. Fresh ethanol is added at the end of the extraction and in inverse flow through the process steps, brought to solid matter.

(9) In a further embodiment, the method of the present invention as described in FIG. 3 and scaled for the laboratory.

(10) 122 g rapeseed (hulled or non-hulled) are suspended in 488 g 96% by vol. ethanol in a 1 l pressure reactor 9. The reactor 9 and the ethanol were preheated to 60 C.

(11) Subsequently, the pressure reactor is closed and the ambient air replaced by nitrogen gas. The cell digestion is carried out by the built-in rotor-stator 1 with the dispersion tool 6 at a rotations speed of 18.8 m s.sup.1.

(12) After 15 min. the seed is completely digested, that is, the average particle size is about 30 m. During the cell digestion, the alcoholic solution was saturated with oil (miscella). The superfluous free oil (oil.sub.1) that could not dissolve is present as free oil droplets in the miscella. Furthermore, the alcohol soluble constituents (phospholipids, oligosaccharides, phenolic compounds and glucosinolate) are dissolved in the miscella and are visible as orange-red color.

(13) The pressure reactor 9 is subsequently pressurized (2-3 bar). Through a built-in filter frit (pore size 15 m), the liquid phase (miscella and free oil) is pressed out and lead into a separating funnel 10. The filtration lasts about 1-2 hours. When stirring the suspension during filtration, the formation of a filter cake is prevented. In this manner, the duration of the filtration is reduced to about 15-30 min. Remaining in the reactor after filtration is a partially deoiled extraction residue with a portion of miscella of 40-60%.

(14) In the separation funnel 10 the liquid phases separate from each other. The orange-red miscella forms the upper phase and the free oil sinks to the bottom. The miscella cools down to room temperature. Thereby, the maximal oil solubility is reduced, that is, the oil dissolved in the miscella partially precipitates and also sinks downward in the separation funnel. Additionally, a third phase, the so-called extraction mix can form in between.

(15) The free oil (oil.sub.1) is drawn from the separation funnel 10. Thereafter the miscella is returned to the pressure reactor 9. In the pressure reactor 9, the miscella is stirred and heated to 60 C. Subsequently, the afore-described filtration steps, the separation of the free oil and the return of the miscella are repeated to the point where after filtration no more free oil (oil.sub.1) remains in the separation funnel.

(16) By applying ultrasound and use of the stirrer, the amount of separated free oil per repeat step can be increased. The total yield of free oil (oil.sub.1) remains almost unchanged. As a result, the input of energy from stirring and ultra sound reduces the number of necessary repeat steps. Laboratory experiments showed that after 2-5 repeats no further free oil remains in the separation funnel.

(17) Instead of the miscella, 488 g fresh alcohol is supplied to the reactor, stirred in the reactor and heated to 60 C. Then, the above-described filtration follows. This washing step of the extraction residue serves to dissolve the last oil residues and alcohol soluble constituents that are present. Depending on need, this washing step can be repeated as a final step.

(18) For the solvent recovery, the entire miscella and the extract mix are gently evaporated in a rotation evaporator. After removal of the ethanol which is retumed to the extraction cycle, a liquid oil phase (oil.sub.2) and an orange-red solid phase, the so-called bottom product (consisting of oil, phospholipids, oligosaccharides, phenolic compounds and glucosinolate) remains in the rotation evaporator. The bottom product is thereafter washed with acetone. An acetone insoluble phase, consisting of phospholipids and the oligosaccharides remains and is separated. In the following step of refining/distillation of the acetone, besides a liquid oil phase (oil.sub.3), a solid phase is also obtained. The solid phase of the acetone-soluble portion consists mainly of phenolic compounds and the glucosinolates.

(19) The alcohol-moist extraction residue (solid content about 40-60%) is dried under gentle conditions. The so-distilled ethanol is returned to the extraction cycle. The dried extraction meal is light colored and poor in sinapine and glucosinolates. This makes the extraction meal more high-quality than extraction meals from the conventional oilseed production. Having a protein content of over 50% and a residual oil content of 3% offers better conditions for the production of high-quality protein preparations as well as high-quality feed stuff.

(20) The replaced oil (oil.sub.1), after separation from the separation funnel contains approximately 6-9% ethanol. After a gentle evaporation, the distilled ethanol is returned to the extraction cycle. In oil.sub.1, the portion of free fatty acids of 0.03-0.6% is very low. Likewise, the phosphorus content of 0.8-7 ppm is very low. In the extracted oils, oil.sub.2 and oils.sub.3, the content of free fatty acids and phosphorus is higher.

(21) In the laboratory experiment, about 70% of oil contained in rapeseed is displaced from the seed (oil.sub.1). The oil portion extracted from the miscella (oil.sub.2) corresponds to about 23% of the oil in the rapeseed. Oil.sub.3 obtained from the acetone soluble portion of the bottom product, corresponds to about 4% of oil contained in the rapeseed. The remaining oil remains as residual content in the extraction meal.

(22) The acetone non-soluble portion of the bottom product and the extraction mix, consisting predominantly of phospholipids and oligosaccharldes, represents the phospholipid-rich phase. This lecithin phase is substantially free of water. The conventional path to lecithin production with the steps of oil desliming and a subsequent elaborate drying process are thus eliminated.

(23) Following is the mass balance illustrated for the sample embodiment. From the starting 122 g hulled rapeseed (3% moisture), the following products are obtained:

(24) 43 g oil.sub.1 (dry, free of ethanol)

(25) 14 g oil.sub.2

(26) 4 g oil

(27) 44 g extraction meal (dry, free of ethanol

(28) 11 g phopholipids+oligosaccharides

(29) 2 g phenolic compounds+glucosinolates

(30) 4 g water, evaporated at drying

(31) In a further embodiment example, the cell digestion is carried out alternatively with high pressure homogenizer. When selecting the cell digestion method it is a decisive factor that it a complete digestion with a particle size of 30 m is attained.

(32) In a further example of an embodiment, the separation of the liquid phase (miscella/free oil) from the extraction residue can be selected such as by means of pressure filtration, screen pressing, screen centrifuge or screen decanter. Significant is the ensure separation of fine- and very fine particles from the digestion. With a correspondingly large separation surface and reduction of filter cake formation, the separation time can be reduced to a minimum.

(33) In a further sample embodiment, the separation of the liquid phase is carried out in a sedimentation tank or by means of a centrifugal force. It is Important that prior to the separation of the free oil, the miscella is cooled to preferably 4-25 C. In a continuous method this is accomplished via a heat exchanger.

(34) In a further example of an embodiment, the extraction is carried out by 1-6 bar, preferably at an ambient pressure below the boiling temperature of the solvent.

(35) In a further example of an embodiment, the alcohol-moist extraction residue is first mechanically pressed and thereafter gently dried in a vacuum dryer.

(36) In a further example of an embodiment, the recovery of the ethanol is carried out by means of vacuum evaporation. Prior to evaporation concentrating the miscella can be done by means of membrane separation method, preferably Ultra-filtration.

(37) In a further example of an embodiment, the digestion of hulled rapeseed is carried out with a dispersion tool 6 and the rotor-stator system 1 in the pressure reactor 9. The dispersion tool 6 was installed with a floor distance of 48 mm. In addition, for improved mixing, four immersion pipes 7 are Integrated into the system as baffles. In pressure reactor 9, optimal conditions were chosen for an effective cell digestion. For the cell digestion in pressure reactor 9, a dispersion period of 15 was chosen, a rotation of 20 000 rpm (circumferential speed 18.8 m s.sup.1) and a solid content of 20%. Additionally, during the cell digestion, pressure of 1 bar was adjusted in the pressure reactor and in the jacket temperature set at 60 C. Prior to the start of the digestion, the pipe line as well as the reactor were rinsed with nitrogen gas via a gas line, in order to render the pipe line and the pressure reactor Inert and to reduce any oxidative processes.

(38) For the cell digestion with subsequent extraction of oil from the digested rape seeds, ethanol (96.0 vol. %) was used. Corresponding to the desired solid content of 20%, ethanol was combined with the hulled rapeseed resulting in 610 g total mass.

(39) In the experiments, to produce the extract in the pressure reactor 9, the ethanol-oil-mixture was pressed out from the pressure reactor 9 by applying super pressure. In order to obtain a most particle-free as possible extract, an inline filter with a pore size of 15 m, was integrated into the system. The filtered extract was captured in a separation funnel 10. It consists of liquid phases miscella and free oil. In this example, the extract-mix phase could not be detected.

(40) After filtration, the extraction residue remaining in pressure reactor 9 had residual moisture of about 50-60%. Depending on the experimental set-up, the residue was dried or combined with ethanol. The suspension was manually homogenized with a spatula and after the pressure reactor was closed in pressure-tight manner, rendered inert with nitrogen. By applying the super pressure, the extraction meal was again filtered. According to the experimental set-up, this step was repeated.