METHOD FOR THE SEPARATE EXTRACTION OF RICE BRAN OIL AND RICE BRAN WAXES

Abstract

A method for the separate extraction of rice bran oil and rice bran wax using supercritical CO.sub.2 as extraction medium and including two separation steps involving different predetermined pressure and temperature conditions.

Claims

1. A method for the separate extraction of rice bran oil and rice bran wax with the following steps: a) an extraction step involving provision an extraction vessel containing rice bran and percolating supercritical CO.sub.2 through the extraction vessel at an extraction pressure within the range of 100 and 1000 bar and at an extraction temperature within the range of 35° C. to 120° C.; b) a first separation step involving transferring the supercritical CO.sub.2 and an extract comprising of oil and waxes from step a) to a first separation vessel and reducing the pressure to a first separation pressure that is lower than the extraction pressure to precipitate a first product comprising rice bran oil from supercritical CO.sub.2; and c) a second separation step involving transferring supercritical CO.sub.2 and remaining extract from step b) to a second separation vessel and reducing the pressure to a second separation pressure that is lower than the first separation pressure to precipitate a second product comprising rice bran wax from a gaseous CO.sub.2.

2. The method according to claim 1, wherein the extraction pressure for the extraction step a) is within the range of 100 and 600 bar.

3. The method according to claim 1, wherein the extraction temperature for the extraction step a) is within the range of 50° C. to 80° C.

4. The method according to claim 1, wherein the first separation step b) is conducted at a first separation temperature that is higher than the extraction temperature of extraction step a).

5. The method according to claim 4, wherein the first separation temperature is at least 65° C.

6. The method according to claim 1, wherein the first separation pressure for the first separation step b) is set below 230 bar.

7. The method according to claim 1, wherein the second separation pressure for the second separation step c) is set below 73.8 bar.

8. The method according to claim 1, wherein the second separation step c) is conducted at a second separation temperature that is lower than the extraction temperature of extraction step a).

9. The method according to claim 8, wherein the second separation temperature is set below 70° C.

10. The method according to claim 1, wherein the extraction step a) is conducted with a solvent/feed ratio within the range of 25 to 45.

11. The method according to claim 1, further comprising a recovery step d), in which the temperature of the gaseous CO.sub.2 after the second separation step c) is decreased to a recovery temperature at which the gaseous CO.sub.2 changes to a liquid state.

12. The method according to claim 11, wherein the recovery temperature is at most 30° C.

13. The method according to claim 11, wherein after the recovery step d), the pressure and the temperature of the liquid CO.sub.2 is increased to the extraction pressure and extraction temperature to change the state of the CO.sub.2 to supercritical for re-use in extraction step a).

Description

[0040] The invention will be further explained based on the attached figures. It will be understood that these figures are intended to describe illustrative embodiments of the invention and are not intended to limit the scope of the invention in any way.

[0041] FIG. 1 shows a schematic drawing of the inventive process; and

[0042] FIG. 2 shows a schematic graphic of the different states of the extraction medium CO.sub.2.

[0043] FIG. 1 shows a schematic representation of the inventive process 1, in which gaseous CO.sub.2 3 is introduced into the process 1 and brought to liquid state at by reducing the temperature to a recovery temperature T4 at a first heat exchanger 5 and stored in a liquid CO.sub.2 storage 7. Using a pump 9, the liquid CO.sub.2 is transferred to a pressure regulated extraction vessel 13 comprising a stock of rice bran 15. Before or within the extraction vessel 13, the pressure is increased to an extraction pressure p1 by means of the pump 9 and the temperature is adjusted to an extraction temperature T1 by means of a second heat exchanger 11. The term “heat exchanger” is thereby to be understood in broad terms. For instance, the extraction vessel 13 can be positioned in a fluid bath (not shown) which during CO.sub.2 loading is filled with a hot fluid to cause an increase in the temperature of the extraction vessel 13 and thus the CO.sub.2 therein. By adjusting the temperature and pressure, the liquid CO.sub.2 is brought into its supercritical state 12. The supercritical CO.sub.2 is then percolated with the stock of rice bran 15 for a time sufficient to ensure impregnation of rice bran oil and rice bran wax in the supercritical CO.sub.2, preferably for 1 to 4 hours. As a result, a rice bran extract comprising rice bran oil and rice bran wax is thereby solubilized in the supercritical CO.sub.2. The supercritical CO.sub.2 loaded with rice bran extract 17 is then transferred through a first check valve 19 to a first separator 21, where the pressure p1 is reduced to a first separation pressure p2 and the temperature T1 is increased to the first separation temperature T2, e.g. by using a third heat exchanger (not shown). The decrease in pressure and increase in temperature causes precipitation of a first product 23, such that the first product 23 is separated from a mixture of supercritical CO.sub.2 and remaining rice bran extract 29. The precipitated first product 23 is passed through a first valve 25 and collected in a first vessel 27. The mixture of supercritical CO.sub.2 and remaining extract 29 is fed through a second check valve 31 to a second separator 33, where the pressure p2 is lowered to a second separation pressure p3 and the temperature T2 is decreased to a second separation temperature T3. For adjusting the temperature to the second separation temperature T3 a further heat exchanger (not shown) can be used. The decrease in the temperature and pressure in the second separator 33 causes the supercritical CO.sub.2 to change into its gaseous state 37 and leads to precipitation of a second product 35 from the gaseous CO.sub.2 37. The second product 35 is passed through a second valve 39 and collected in a second vessel 41. The gaseous CO.sub.2 37 is transferred back to the first heat exchanger 5, at which the temperature can be decreased further to bring the gaseous CO.sub.2 into liquid state for storage.

[0044] FIG. 2 shows a schematic graph of the different states of CO.sub.2 at different pressure and temperature conditions. At high pressure and low temperature, the CO.sub.2 is in a solid state 101 known as dry ice. In contrast thereto, at low pressure and high temperature, CO.sub.2 is in a gaseous state 103. Within a temperature range of −56.6° C. to 31.0° C. and a pressure above 5.2 bar CO.sub.2 will predominantly be in a liquid state 105. To bring the CO.sub.2 into its supercritical state 111, a pressure of at least 73.8 bar and a temperature of at least 31.0° C. is required.

[0045] The above changes of CO.sub.2's aggregation states are utilized in the method of the present invention: For the extraction step a) of the inventive process, CO.sub.2 is brought to supercritical state 111 at the extraction pressure p1 112 and the extraction temperature T1 113. In the first separation step b), the pressure of the supercritical CO.sub.2 111 is lowered to the first separation pressure p2 and the temperature is increased to the first separation temperature T2 114, 115. During the second separation step c), the pressure and the temperature are lowered to the second separation pressure p3 and the second separation temperature T3 116, 117, respectively, at which the CO.sub.2 changes to a gaseous state 103. In the recycling step d), the temperature of the gaseous CO.sub.2 is further reduced to the recovery temperature T4 119, at which the CO.sub.2 changes to a liquid state 105. The liquid CO.sub.2 can then be reused for the extraction in the extraction step a) by increasing the temperature and pressure to the extraction pressure p1 and extraction temperature T1 112, 113, respectively, to bring the CO.sub.2 into supercritical state 111 again.

Materials and Methods

EXAMPLE 1

Extraction Process

[0046] Raw stabilized rice bran (10 kg from FortiBran® as FORTIVIA® N° 09-050-2019-22) was introduced in an extraction basket, then placed in an extractor. The extractor was pressurized to an extraction pressure p1 of 280 bar. Supercritical CO.sub.2 (267 kg) was percolated through the raw rice bran in the extractor at the extraction pressure and at an extraction temperature T1 of 60° C. The solvent/feed ratio was 36.

[0047] In Example 1, the rice bran contained an initial oil/wax content of 15% oil and 3% waxes.

Separation Process

[0048] The supercritical CO.sub.2 and the extract solubilized therein were transferred to a first separation vessel. The pressure was reduced to a first separation pressure p2 of 180 bar and the temperature was increased to a first separation temperature T2 of 75° C. This caused rice bran oil to precipitate from the supercritical CO.sub.2 and was collected at the bottom of the separation vessel.

[0049] The supercritical CO.sub.2 and remaining extract were transferred to a second separation vessel and the pressure was reduced to a second separation pressure p3 of 60 bar and the temperature was reduced to a second separation temperature T3 of 50° C. At these conditions, rice bran wax precipitated (mostly in liquid state) from gaseous CO.sub.2 and was collected at the bottom of the second separation vessel.

[0050] The first and second products comprising rice bran oil and rice bran wax were collected in separators in real time. After separation, water was removed from the precipitated products by decantation at 70° C.

[0051] Yields of rice bran oil were determined by gravimetry and other analytical methods including fatty acid titration.

[0052] Yield of the collected rice bran oil and rice bran wax after decantation and water removal was 15% and 3%, respectively. Total yield of rice bran oil and wax was thus 18%.

[0053] The conditions and yields of Example 1 are summarized in Table 1 below:

TABLE-US-00001 Separation Yield after Extraction Conditions Conditions water removal Temp. Solvent/ p2/T2 p3/T3 (decantation) Pressure T1 Feed in 1.sup.st in 2.sup.nd Yield after Total p1 (bar) (° C.) ratio stage stage sep. stage yield 280 60 36 180 bar 60 bar 1.sup.st 15% 18% 75° C. 50° C. stage 2.sup.nd  3% stage

EXAMPLE 2—LOW PRESSURE AND TEMPERATURE CONDITIONS

Material

[0054] Raw stabilized rice bran (FortiBran®—long grain rice type A Rombo, stabilized by vapor at 8 bar during 30 seconds, (by FORTIVIA®)) was used as starting material.

[0055] Preliminary note: The contents of rice bran oil and wax can vary quite significantly. The rice bran used for Example 2 had the same rice bran oil content as the one used for Examples 1 and 3, namely 15%, yet the initial rice bran wax content was found to be significantly lower, namely merely 0.5% instead of 3%.

[0056] In Example 2, the extraction and separation steps were carried out same way as for Example 1, yet with the conditions indicated in Table 2 below. The purpose of this Example 2 was to verify that a separate extraction of rice bran oil and rice bran wax was possible with a very low pressure and temperature. For this purpose, only a small fraction of rice bran oil was actually extraction and collected in the 1.sup.st separation stage. In the 2.sup.nd separation stage, it was tried to extract and separate as much rice bran wax as possible.

[0057] The conditions and yields of Example 2 are summarized in Table 2 below:

TABLE-US-00002 Extraction Separation Conditions Conditions Yield after water Solvent/ p2/T2 p3/T3 removal (decantation) p1 T1 Feed in 1.sup.st in 2.sup.nd Yield after Total [bar] [° C.] ratio stage stage sep. stage yield .sup.(**) 100 35 25 90 bar 60 bar 1.sup.st 0.55% .sup.(**) 1.1% .sup.(**) 60° C. 60° C. stage 2.sup.nd 0.45% stage

[0058] It was found that a separate extraction of rice bran oil and wax was possible under low pressure and temperature conditions (100 bar and 35° C.).

[0059] (**)While only a fraction of light rice bran oils was actually separated and collected during the first separation stage (0.55% of overall 15%), it could be verified that separation and extraction of essentially all rice bran wax contained in the raw rice bran was possible (0.45% of overall 0.5%).

EXAMPLE 3—HIGH PRESSURE AND TEMPERATURE CONDITIONS

Material

[0060] Raw stabilized rice bran (from FortiBran® as FORTIVIA® N° 09-050-2019-22) was used as starting material (i.e. the same as in Example 1). The rice bran contained an initial oil/wax content of 15% oil and 3% waxes.

[0061] In Example 3, the extraction and separation steps were carried out same way as for Example 1, yet with the conditions indicated in Table 3 below.

[0062] The conditions and yields of Example 3 are summarized in Table 3 below:

TABLE-US-00003 Separation Yield after water Extraction Conditions Conditions removal (decantation) p1 T1 Solvent/ p2/T2 in p3/T3 in Yield after Total (bar) (° C.) Feed ratio 1.sup.st stage 2.sup.nd stage sep. stage yield 550 80 12 250 bar 60 bar 1.sup.st 17% 20% 80° C. 50° C. stage 2.sup.nd  3% stage

[0063] It was found that at high pressure and a smaller solvent/feed ratio, a higher overall extraction yield was obtained (total 20% instead of 18%). It is assumed that all rice bran oil and waxes were extracted, yet together with some other compounds that were not co-extracted at lower pressure. This assumption is based on the observance that rice bran oil was effectively collected during the 1st separation stage, together with some other compounds, inter alia pigments and polar lipids. All waxes were collected during the 2.sup.nd separation stage.