Organic compounds -- part of the class 532-570 series – Organic compounds – Fatty compounds having an acid moiety which contains the...
Reexamination Certificate
1998-08-14
2001-06-19
Vollano, Jean F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Fatty compounds having an acid moiety which contains the...
C554S174000, C554S175000, C554S192000, C554S196000
Reexamination Certificate
active
06248911
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to the refinement of glyceride oils and particularly to the removal of soaps, phospholipids, detrimental metals, and chlorophyll from such oils.
BACKGROUND OF THE INVENTION
Crude glyceride oils, particularly vegetable oils, are typically refined by a multi-stage process. The first stage of this process typically is degumming by treatment with water or with a chemical such as phosphoric acid, citric acid, or acetic anhydride. Gums (or “phospholipids”) include such substances as lecithin and cephalin. About 90% of gums present in crude glyceride oils are capable of being hydrated and therefore are easily removed by a water wash. The remaining 10% can be converted to hydratable forms by the use of phosphoric acid as the degumming agent. Although gums may be separated from the oil at this point or carried into subsequent phases of refining, oil which has been subjected to this degumming step is said to be “degummed” herein. Various chemicals and operating conditions have been used to perform hydration of gums for subsequent separation.
After degumming (or instead of degumming), the oil may be refined by a chemical process including neutralization, bleaching, and deodorizing steps. Alternatively, a physical process may be used, including a pretreating and bleaching step and a steam refining and deodorizing step. Regardless of the particular refining process, it is desirable to reduce the levels of phospholipids, soaps (e.g., sodium oleate), and detrimental metals, all of which can adversely affect colors, odors, and flavors in the finished oil. Such detrimental metals include calcium, iron, and copper, whose ionic forms are thought to be chemically associated with phospholipids (and, possibly, heavy metal soaps) and to negatively affect the quality and stability of the final oil product. It is also desirable to reduce the level of chlorophyll which, if remaining in the oil, can tend to impart an unacceptably high level of green coloring to the oil as well as possibly causing instability of oil upon exposure to light.
Efforts have been made to remove phospholipids, detrimental metal ions, and chlorophyll from oil. For example, U.S. Pat. No. 4,629,588 discloses the use of untreated amorphous silica, and U.S. Pat. No. 4,734,226 discloses the use of an organic acid-treated amorphous silica, as adsorbents of phospholipids and certain metal ions. According to the '226 patent, organic acids, such as citric, acetic, ascorbic, or tartaric acids, are contacted with amorphous silica in a manner which causes at least a portion of the organic acid to be retained within the pores of the silica. According to another patent, namely U.S. Pat. No. 4,781,864, an acid-treated amorphous silica adsorbent is capable of removing both phospholipids and chlorophyll from glyceride oil. According to this patent, a fairly strong acid having a pK
a
of about 3.5 or lower is contacted with amorphous silica, and the resulting acid-treated amorphous silica has a pH of 3.0 or lower. The acidic conditions during which the acid-treated amorphous silica is prepared tends to result in the precipitation of metal oxides, especially iron oxide, within the pores of the silica and around the silica particles.
Soaps have been removed from oil in the past by a water wash step of up to 15% (by volume) of the oil being purified. A drawback of this method is that the wash effluent water must be regenerated if it is to be used again in a subsequent stage. Accordingly, it is desirable to utilize an adsorbent which minimizes or eliminates the need for a water wash step for the removal of soap.
It is also desirable to utilize an adsorbent which is capable of reducing the levels of phospholipids, soaps, detrimental metals, and chlorophyll in refining oil. In addition, it is desirable to minimize the amount of adsorbent required, because the adsorbent is eventually separated from the oil before the oil is used. When less adsorbent is used, filtration of the adsorbent is easier and less energy-intensive and tends to minimize oil losses in the filtercake.
SUMMARY OF THE INVENTION
In view of its purposes, the present invention provides a process and composition for removing certain contaminants from glyceride oil. The process of the present invention involves contacting a glyceride oil with an adsorbent comprising a metal-substituted silica xerogel having a pH of at least 7.5 to adsorb at least a portion of the contaminants onto the adsorbent, then separating the adsorbent from the oil. The silica xerogel is metal-substituted in that substantially all of the sodium or potassium ions on and within the silica particles are replaced by certain metal ions, such as magnesium. Even more preferably, the adsorbent also includes an organic acid blended with the metal-substituted silica xerogel prior to the step of contacting the oil with the adsorbent. Even more preferably, the organic acid is citric acid.
The composition of the present invention is an adsorbent comprising a metal-substituted silica xerogel having a pH of at least 7.5 and an organic acid blended with the xerogel. Preferably, the organic acid is citric acid, and the substituting metal is magnesium.
The process and composition of the present invention provide for the removal of certain trace contaminants from glyceride oil during the refinement of the oil. These contaminants include phopholipids, soaps, metal ions, and chlorophyll.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, but not restrictive, of the invention.
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Gutfinger, T. and Letan, A., Pretreatment of Soybean Oil for Physical Refining: Evaluation of Efficiency of Various Adsorbents in Removing Phospholipids and Pigments,Journal of the American Oil Chemists' Society,vol. 55, Dec., 1978, pp. 856-859.
Brozzetti Adam J.
Canessa Carlos E.
PQ Corporation
Ratner & Prestia
Vollano Jean F.
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