Methods for treating phosphatide-containing mixtures

Details Methods for treating phosphatide-containing mixtures Methods for treating phosphatide-containing mixtures

2001-02-02

2002-07-30

Carr, Deborah D. (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Fatty compounds having an acid moiety which contains the...

C554S198000, C554S212000

Reexamination Certificate

active

06426423

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to improved methods for treating phosphatide-containing mixtures. More particularly, this invention relates to methods for recovering purified vegetable oil, aqueous organic acid, and organic acid-treated phosphatide from a phosphatide-containing mixture comprising an acid-and-oil mixture obtained from organic acid refining of vegetable oil.
BACKGROUND OF THE INVENTION
Vegetable oils are typically obtained by pressing or extracting the oil seeds of plants such as corn or soybeans. Properly processed vegetable oils are suitable for use in many edible oil and fat compositions destined for human consumption. Such edible oils and fats include salad oils, cooking oils, frying fats, baking shortenings, and margerines. In addition to being widely used in edible oils and fats, vegetable oils are also increasingly utilized in important industrial products such as caulking compounds, disinfectants, fungicides, printing inks, and plasticizers.
Vegetable oils primarily consist of triglycerides, also termed triacylglycerols. In addition to triglycerides, however, vegetable oils also contain several other compounds. Some of these additional compounds, such as mono- and di-glycerides, tocopherols, sterols, and sterol esters, need not necessarily be removed during processing. Other compounds and impurities such as phosphatides, free fatty acids, odiferous volatiles, colorants, waxes, and metal compounds negatively affect taste, smell, appearance and storage stability of the refined oil, and hence must be removed. Carefully separated, however, some of these additional compounds, particularly the phosphatides, are valuable raw materials. It is therefore important to select a vegetable oil purifying method that maximizes removal of impurities but does so in a way that least impacts the compounds removed.
Vegetable oil triglycerides are esters of 1,2,3-propane triol, and can be represented by the generic formula
where R
1
, R
2
, and R
3
are the same or different, and are selected from the group consisting of C
10
-C
22
saturated and unsaturated fatty acids. In soybean oil in particular, the saturated fatty acids that can occur include but are not limited to lauric (C12:0), myristic (C14:0), palmitic (C16:0), stearic (C18:0), arachidic (C20:0), and behenic (C22:0) acids. Generally, however, the fatty acids of soybean oil are predominantly unsaturated, and include but are not limited to oleic (C18:1), linoleic (C18:2), and linolenic (C18:3) acids. Unsaturated fatty acids can exist as geometric and/or positional isomers, each such isomer having different properties such as melting point. Naturally occurring fatty acids generally exist in the cis form, but they can be converted into the trans form during the course of purification steps used to produce a vegetable oil from an oilseed. Crude soybean oil in particular typically contains from about 95 to about 97 percent by weight triglycerides.
The terms phosphatides and phosphatide concentrates are commonly used to refer to a mixture of phospholipids comprising phosphatidyl derivatives which are present in crude vegetable oil. Phosphatides are also called gums, wet gums, lecithin, and wet lecithin. The term lecithin, from a true chemical sense, refers to phosphatidyl choline. However, as used by commercial suppliers, the term lecithin refers to a product derived from vegetable oils, especially soybean oil. Specific chemical components of phosphatides present in vegetable oil include phosphatidyl choline, 1; phosphatidylethanolamine, 2; phosphatidylinositol, 3; phosphatidyl serine, 4; phosphatidic acid, 5; cyclolipids, and other components such as free sugars, metals and free fatty acids.
Such phosphatides are amphipathic, i.e., one end of the molecule is hydrophilic (lipophobic) and the other end is hydrophobic (lipophilic). As a result, they possess useful surface-active properties, and can orient in aqueous environments to create membranes and bilayers.
The fatty acid content of the phosphatides 1 through 5 is represented by R
1
and R
2
, as defined above, and generally matches that of the vegetable oil from which they are derived. The phosphatide content of vegetable oil will vary based on a number of factors, including but not limited to oilseed type, seed quality, and the process by which oil is extracted therefrom. Crude soybean oil in particular typically contains from about 1.5 to about 3 percent by weight phosphatides. Phosphatides comprise both hydratable phosphatides (HPs) and non-hydratable phosphatides (NHPs). Although non-hydratable phosphatides tend to remain oil-soluble and are largely unaffected by water, hydratable phosphatides when hydrated become greater in density than the triglycerides and precipitate, or settle out. This phenomenon forms the basis for the process of conventional water degumming, discussed more fully below.
Vegetable oil impurities are typically removed in four distinct steps of degumming, refining, bleaching, and deodorizing. Of these four steps, degumming removes the largest amount of impurities, the bulk of which are hydratable phosphatides. Refining primarily removes non-hydratable phosphatides, soaps created from the neutralization of free fatty acids, and other impurities such as metals. Bleaching then improves the color and flavor of refined oil by decomposing peroxides and removing oxidation products, trace phosphatides, and trace soaps. Soybean oil bleaching materials include neutral earth (commonly termed natural clay or fuller's earth), acid-activated earth, activated carbon, and silicates. Deodorizing is the final processing step and prepares the oil for use as an ingredient in many edible products including salad oils, cooking oils, frying fats, baking shortenings, and margerines. The deodorizing process generally comprises passing steam through refined oil at high temperature and under near vacuum conditions to vaporize and carry away objectionable volatile components.
Vegetable oil refining, also known as neutralization or deacidification, essentially involves removing free fatty acids (FFA) and phosphatides from the vegetable oil. Most refining operations employ either alkali refining (also termed caustic refining) or physical refining (also termed steam refining). Of these two refining methods, alkali refining predominates.
For either refining method, an optional but preferred first step is a conventional water degumming process. Degumming refers to the process of removing hydratable phosphatides and other impurities such as metals from vegetable oils. A simple degumming process comprises admixing soft water with the vegetable oil and separating the resulting mixture into an oil component and an oil-insoluble hydrated phosphatides component (frequently referred to as a “wet gum” or “wet lecithin”). The NHPs, generally considered to be calcium and magnesium salts of phosphatidic acids, are largely unaffected by water and remain soluble in the oil component. Phosphatidic acids are typically produced via the action of phospholipidase D, which splits off the non-fatty-acid moiety from phospholipids.
Normally, refiners also must introduce chelating agents following degumming processes to remove metal compounds from crude vegetable oil, which typically contains calcium, potassium, magnesium, aluminum, iron and copper. Left in place, these metal impurities form salts of phosphatidic acid, thereby contributing to the NHP content. Moreover, metal contaminants, especially iron, can darken oil during deodorization, and even small amounts of iron that do not affect the oil's color can nevertheless dramatically reduce stability of refined oil.
Treating crude vegetable oil with soft water produces a degummed oil and a phosphatide concentrate containing the hydratable phosphatide fraction. This phosphatide concentrate subsequently can be removed from the degummed oil by a convenient method such as by gravitational force or by centrifugal separation. Phosphatide concentrates coming from centrifugal separation will generally contain up to about fifty

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