Purification of Cooking Oils and Fats with Amino-Functionalized Silica Adsorbent Materials

Abstract

A method of purifying cooking oil or fat by contacting the cooking oil or fat with at least one amino-functionalized silica adsorbent material, wherein the at least one amino-functionalized silica adsorbent material is not in the form of a cationic species. Such method provides for improved removal of free fatty acids from the cooking oil or fat without generating or producing soaps.

Claims

1. A method of purifying cooking oil or fat, comprising: contacting said cooking oil or said fat with at least one amino-functionalized silica adsorbent material, wherein said at least one amino-functionalized silica adsorbent material is not in the form of a cationic species, wherein said cooking oil or said fat is contacted with said amino-functionalized silica adsorbent material in an amount effective to purify said cooking oil or said fat.

2. The method of claim 1 wherein said at least one amino-functionalized silica adsorbent material is produced by reacting at least one silica material with at least one reactive aminoalkylsilane.

3. The method of claim 2 wherein said at least one silica material is selected from the group consisting of silica gel, magnesium silicate, calcium silicate, sodium silicate, aluminum silicate, sodium aluminum silicate, and combinations thereof.

4. The method of claim 3 wherein said at least one silica material is magnesium silicate.

5. The method of claim 2 wherein said at least one reactive aminoalkylsilane is selected from the group consisting of 3-aminopropyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyldimethylethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyldimethylmethoxysilane, 3-aminopropyltrichlorosilane, 3-aminopropylmethyldichlorsilane, 3-aminopropyldimethylchloroxysilane, 4-aminobutyltriethoxysilane, 4-aminobutylmethyldiethoxysilane, 4-aminobutyldimethylethoxysilane, 4-aminobutyltrimethoxysilane, 4-aminobutylmethyldimethoxysilane, 4-aminobutyldimethylmethoxysilane, 4-aminobutyltrichlorosilane, 4-aminobutylmethyldichlorsilane, 4-aminobutyldimethylchloroxysilane, 3-(2-aminoethylamino)propyltriethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, 3-[2-(2-aminoethylamino)ethylamino]propyltriethoxysilane, and 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane.

6. The method of claim 5 wherein said at least one reactive aminoalkylsilane is selected from the group consisting of 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane.

7. The method of claim 5 wherein said at least one reactive aminoalkylsilane is selected from the group consisting of 3-(2-aminoethylamino)propyltriethoxysilane and 3-(2-aminoethylamino)propyltrimethoxysilane.

8. The method of claim 5 wherein said at least one reactive aminoalkylsilane is selected from the group consisting of 3-[2-(2-aminoethylamino)ethylamino]propyltriethoxysilane and 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane.

9. The method of claim 3 wherein said at least one silica material is silica gel.

10. The method of claim 1 wherein said at least one amino-functionalized silica adsorbent material has an amino content of at least 0.001 millimoles per gram.

11. The method of claim 10 wherein said at least one amino-functionalized silica adsorbent material has an amino content of from about 0.01 millimoles per gram to about 4.0 millimoles per gram.

12. The method of claim 1 wherein said at least one amino-functionalized silica adsorbent material has a pH in a 5% slurry of from about 8.0 to about 11.5.

13. The method of claim 12 wherein said at least one amino-functionalized silica adsorbent material has a pH in a 5% slurry of from about 9.0 to about 10.0.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The invention now will be described with respect to the drawings, wherein:

[0032] FIG. 1 is a graph showing the amounts of residual free fatty acids after treating used cooking oil containing 1.0 wt. % free fatty acids with two commercially available aminopropyl-functionalized silica gels, and are compared to an unmodified silica gel;

[0033] FIG. 2 is a graph showing the amounts of residual free fatty acids after treatment of an oil containing 1.0 wt. % free fatty acids with the aminopropyl-functionalized silica gels of Examples 3 through 5, as compared to an unmodified silica gel;

[0034] FIG. 3 is a graph showing a comparison of the amounts of residual free fatty acids after treatment of an oil containing 1.0 wt. % free fatty acids with the aminopropyl-functionalized silica gel of Example 5 with Commercial Product 1 (Comparative Example 1) and Commercial Product 2 (Comparative Example 2);

[0035] FIG. 4 is a graph showing the amounts of residual soap after treatment of an oil containing 1.0 wt. % free fatty acids with either the aminopropyl-functionalized silica gel of Example 5, Commercial Product 1, or Commercial Product 2;

[0036] FIG. 5 is a graph showing the amounts of residual free fatty acids after treatment of a used cooking oil containing 1.0 wt. % free fatty acids with either unmodified silica gel, or the 3-(ethylenediamino) propyl-functionalized silica gels of Examples 6 and 7;

[0037] FIG. 6 is a graph showing the amounts of residual free fatty acids after treatment of an oil containing 1.0 wt. % free fatty acids with the commercially obtained 3-(diethylenetriamino) propyl-functionalized silica gel of Example 8, as compared to an unmodified silica gel; and

[0038] FIG. 7 is a graph showing the amounts of residual free fatty acids after treatment of an oil containing 1.0 wt. % free fatty acids with samples of aminopropyl-functionalized magnesium silicate (Examples 9, 10, and 11), or an unmodified magnesium silicate.

EXAMPLES

[0039] The invention now will be described with respect to the following examples. It is to be understood, however, that the scope of the present invention is not intended to be limited thereby.

[0040] Eleven different amino-functionalized silica adsorbents were tested for removal of free fatty acids from a preheated cooking oil using a front-loading method of oil treatment. The front-loading method of oil treatment used a Modified Gelman Filter apparatus that mimicked a restaurant three-vat fryer setup. 3.6 grams of adsorbent powder were used to treat preheated oil that was divided into three equal amounts (60 grams) followed by sequential filtrations with 5 minutes of oil circulation per filtration. This oil treatment was a 2 wt. % dosing of adsorbent based on the total weight (180 grams) of the oil that was treated. The oil collected at the end of each cycle was analyzed for residual free fatty acids and soap by standard titration methods.

[0041] The eleven amino-functionalized silica materials tested were as follows:

Example 1

[0042] 3 aminopropyl-functionalized silica gel having a particle size of 40 to 63 microns and an amine loading of about 1 mmol NH.sub.2/g adsorbent, obtained from Sigma-Aldrich.

Example 2

[0043] 3 aminopropyl-functionalized silica gel having a particle size of 40 to 63 microns, and an amine loading of about 1.4 mmol NH.sub.2/g adsorbent, obtained from ACROS Organics.

Example 3

[0044] 100 g of silica gel having a particle size of 40 to 63 microns, 20 g of water, and 200 g of ethanol were charged into a 1 liter reactor. The mixture was stirred and heated to 75 C. 31.3 g of 3-aminopropyltriethoxysilane were mixed with 63 g of ethanol, and added slowly to the mixture over 35 minutes. The mixing was continued for 3 hours at 75 C., and then the mixture was cooled to 40 C. The resulting suspension was vacuum filtered using a Buchner funnel over a Whatman #2 filter paper. The resulting wet cake was washed with 400 g of water, followed by 400 g of ethanol. The material then was placed in an oven and dried at 107 C. for 6 hours. Target amine loading was 1.4 mmol NH.sub.2/g adsorbent.

Example 4

[0045] An aminopropyl-functionalized silica gel was prepared in accordance with Example 3, except that 44.7 g of 3-aminopropyltriethoxysilane mixed with 90 g of ethanol were used. Target amine loading was 2.0 mmol NH.sub.2/g adsorbent.

Example 5

[0046] An aminopropyl-functionalized silica gel was prepared in accordance with Example 3 except that 62.6 g of 3-aminopropyltriethoxysilane mixed with 125.0 g of ethanol were used. Target amine loading was 2.8 mmol NH.sub.2/g adsorbent.

Example 6

[0047] 3-(ethylenediamino) propyl-functionalized silica gel having an amine loading of 0.8 mmol NH.sub.2/g adsorbent, obtained from ACROS Organics.

Example 7

[0048] 3-(ethylenediamino) propyl-functionalized silica gel having an amine loading of 1.4 mmol NH.sub.2/g adsorbent, obtained from TCI America.

Example 8

[0049] 3-(diethylenetriamino) propyl-functionalized silica gel having an amine loading of 1.4 mmol NH.sub.2/g adsorbent, obtained from Sigma Aldrich.

Example 9

[0050] 100 g of an amorphous hydrous precipitated synthetic magnesium silicate, treated to reduce the pH thereof to less than 9.0, and manufactured under the trade name Magnesol XL by the Dallas Group of America, Inc., Whitehouse, N.J., and described in U.S. Pat. No. 5,006,356, 20 g of water, and 200 g of ethanol were charged into a 1 liter reactor. The mixture was stirred and heated to 75 C. 11.2 g of 3-aminopropyltriethoxysilane was mixed with 25 g of ethanol and added slowly to the mixture in the reactor over 35 minutes. Mixing was continued at 75 C. for 3 hours, and then the mixture was cooled to 40 C. The resulting suspension was vacuum filtered using a Buchner funnel over a Whatman #2 filter paper. The resulting wet cake was washed with 400 g of water, followed by 400 g of ethanol. The material then was placed in an oven and dried at 107 C. for 6 hours. Target amine loading was 0.5 mmol NH.sub.2/g adsorbent.

Example 10

[0051] An aminopropyl-functionalized magnesium silicate was prepared in accordance with Example 9 except that 33.5 g of 3-aminopropyltriethoxysilane mixed with 67 g of ethanol were used. Target amine loading was 1.5 mmol NH.sub.2/g adsorbent.

Example 11

[0052] An aminopropyl-functionalized magnesium silicate was prepared in accordance with Example 9 except that 67.0 g of 3-aminopropyltriethoxysilane mixed with 135 g of ethanol were used. Target amine loading was 3.0 mmol NH.sub.2/g adsorbent.

Comparative Example 1

[0053] Commercial Product 1, a blend of sodium silicate and silica gel.

Comparative Example 2

[0054] Commercial Product 2, a blend of sodium silicate and silica gel.

Results

[0055] The aminopropyl-functionalized silica gels were evaluated for free fatty acid removal by the front-loading oil treatment method. Restaurant-used frying oil was treated with the functionalized silica gel placed on filter media (Oberlin EVO 80) in the Modified Gelman Filter Apparatus. Three sequential filtrations using oil (60 g) preheated to 325 F. were performed on the material (3.6 g) and the oil was circulated for 5 minutes per filtration cycle. The oil collected at the end of each cycle was analyzed for residual free fatty acids and soap by standard titration methods.

[0056] FIG. 1 shows residual free fatty acids after treatment of used frying oil containing 1.0% free fatty acids with two commercially available aminopropyl-functionalized silica gel materials and are compared to unmodified silica gel having the same particle size. No residual soap was produced during this treatment. As shown in FIG. 1, the aminopropyl-functionalized silica gels of Examples 1 and 2 provided for improved removal of free fatty acids when compared to an unmodified silica gel.

[0057] The preparation of 3-aminopropyl functionalized silica gel materials were achieved by using slurry/suspension methods. Three AP-Silica gels materials were prepared, which targeted 1.4, 2.0, and 2.8 mmol/g of amine loading.

[0058] The aminopropyl-functionalized silica gels were evaluated for free fatty acid removal by the front-loading oil treatment method. Used restaurant frying oil having about 1.0% free fatty acids with no soap (0 ppm) was treated with amino-functionalized silica gel placed on filter media (Oberlin EVO 80) in the Modified Gelman Filter Apparatus. Three successive filtrations using oil (60 g) preheated to 325 F. were performed on the material (3.6 g) and the oil was circulated for 5 minutes per filtration cycle. The oil collected at the end of each cycle was analyzed for residual free fatty acids and soap by standard titration methods.

[0059] FIG. 2 shows residual free fatty acids after treatment of an oil containing 1.0% free fatty acids with the aminopropyl-functionalized silica gels of Examples 3 through 5. These silica gels were compared to unmodified silica gel. The aminopropyl-functionalized silica gels of Examples 3, 4, and 5 provided for improved removal of free fatty acids when compared to the unmodified silica gel.

[0060] FIG. 3 shows a comparison of residual free fatty acids after treatment of an oil containing 1.0% free fatty acids with the aminopropyl-functionalized silica gel of Example 5 to Commercial Product 1 and Commercial Product 2.

[0061] Although Commercial Products 1 and 2 provided favorable results for free fatty acid removal compared to the aminopropyl-functionalized silica gel of Example 5, Commercial products 1 and 2 produced large amounts of soaps, due to the presence of sodium silicate, which are not removed by filtration as shown in FIG. 4.

[0062] FIG. 4 shows a comparison of residual soap after treatment of an oil containing 1.0% free fatty acids with the aminopropyl-functionalized silica gel of Example 5 to Commercial Product 1 and Commercial Product 2. The aminopropyl-functionalized silica gel of Example 5 did not produce any soap (The materials contain no alkali or alkaline materials.), whereas Commercial Product 1 and Commercial Product 2 produced significant amounts of soap. Residual soaps at high levels (above 200 ppm) can create excess foaming in frying oils and fats, which can be problematic when deep frying food and in addition residual soaps in frying oil catalyze degradation of oil during frying.

[0063] FIG. 5 shows a comparison of residual free fatty acids after treatment of used restaurant oil having 1.0% free fatty acids with the 3-(ethylenediamino) propyl-functionalized silica gels of Examples 6 and 7 to unmodified silica gel. No residual soap was detected. The amino-functionalized silica gels of Examples 6 and 7 provided for improved removal of free fatty acids compared to unmodified silica gel.

[0064] FIG. 6 shows a comparison of residual free fatty acids after treatment of an oil containing 1.0% free fatty acids treated with the 3-(diethylenetriamino) propyl-functionalized silica gel of Example 8 to unmodified silica gel. Improved removal of free fatty acids was provided by the amino-functionalized silica gel of Example 8, compared to the unmodified silica gel.

[0065] The functionalization of synthetic magnesium silicate (Magnesol XL, The Dallas Group of America, Inc., Whitehouse, N.J.) with 3-aminopropyltriethoxysilane was performed by a slurry/suspension method in water and ethanol as hereinabove described, in order to prepare magnesium silicates with amine loadings of 0.5 mmol/g (Example 9), 1.5 mmol/g (Example 10), and 3.0 mmol/g (Example 11).

[0066] FIG. 7 shows residual free fatty acids after treatment of a frying oil containing 1.0% free fatty acids with the amino-functionalized synthetic magnesium silicates of Examples 9, 10, and 11, as compared to unmodified synthetic magnesium silicate (Magnesol XL). In general, the amino-functionalized magnesium silicates provided for improved removal of free fatty acids compared to the unmodified magnesium silicate.

[0067] Table 1 shows nitrogen content from elemental analysis, calculated amine loading, and pH of prepared aminopropyl-functionalized silica gels and magnesium silicates and are compared to unmodified raw materials.

TABLE-US-00001 TABLE 1 Amine Loading Based on Elemental Elemental Analysis, % Analysis, Nitrogen mmol/g pH Silica Gel 0 0 6.2 AP-Silica Gel (Target 1.4 mmol/g), 1.70 1.33 9.1 Example 3 AP-Silica Gel (Target 2.0 mmol/g), 2.25 1.82 9.6 Example 4 AP-Silica Gel (Target 2.8 mmol/g), 2.67 2.23 10.0 Example 5 Magnesium Silicate (Magnesol XL) 0 0 9.0 AP-Magnesium Silicate (Target 0.5 0.74 0.54 10.0 mmol/g), Example 9 AP-Magnesium Silicate (Target 1.5 2.04 1.63 11.1 mmol/g), Example 10 AP-Magnesium Silicate (Target 3.0 2.33 2.05 10.6 mmol/g), Example 11

[0068] Table 2 shows BET surface area and total pore volume data of prepared aminopropyl-functionalized silica gels and magnesium silicates and are compared to unmodified raw materials.

TABLE-US-00002 TABLE 2 BET Surface Area, Total Pore m.sup.2/g Volume, cc/g Silica Gel 536 0.768 AP-Silica Gel (Target 1.4 mmol/g), 355 0.544 Example 3 AP-Silica Gel (Target 2.0 mmol/g), 353 0.483 Example 4 AP-Silica Gel (Target 2.8 mmol/g), 339 0.440 Example 5 Magnesium Silicate (Magnesol XL) 566 0.680 AP-Magnesium Silicate (Target 0.5 565 0.677 mmol/g), Example 9 AP-Magnesium Silicate (Target 1.5 397 0.575 mmol/g), Example 10 AP-Magnesium Silicate (Target 3.0 154 0.340 mmol/g), Example 11

[0069] The disclosures of all patents and publications, including published patent applications, are hereby incorporated by reference to the same extent as if each patent and publication were incorporated individually by reference.

[0070] It is to be understood, however, that the scope of the present invention is not to be limited by the specific embodiments described above. The invention may be practiced other than as particularly described and still be within the scope of the accompanying claims.