Methods for recovering fatty acids

Details Methods for recovering fatty acids Methods for recovering fatty acids

2001-03-14

2002-07-23

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...

C554S212000

Reexamination Certificate

active

06423857

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to improved methods for recovering free fatty acids during purification of vegetable oil. More particularly, this invention relates to improved methods for recovering free fatty acids from a phosphatide-containing material obtained from organic acid refining of vegetable oil.
BACKGROUND OF THE INVENTION
Free fatty acids and phosphatides are two of several byproducts recoverable during the purification of vegetable oil. Vegetable oils are typically obtained by pressing or extracting the oil seeds of plants such as corn or soybeans. 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.
Vegetable oil triglycerides are esters of 1,2,3-propane triol, also termed glycerol, 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, composed primarily of unsaturated fatty acids, together with usually not more than about 1.5 percent by weight free fatty acids and from about 1.5 to about 3 percent by weight of phosphatides, depending on the kind and quality of soybean and oilseed processing procedures.
Free Fatty Acids
The free fatty acid content of a vegetable oil comprises the amount of fatty acid present in an uncombined state as a chemical unit, i.e., not esterified on the glycerol backbone of triglycerides or phosphatides. Free fatty acids originate from the breakdown of triglycerides into its component fatty acid and glycerol units, and result from exposure of triglycerides to moisture and/or from enzymatic processes triggered by damage to the oilseed, such damage caused for example by splitting, breaking, or by heating or other damage induced during storage.
The free fatty acid 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 vegetable oil typically contains from about 0.2 and to about 5 percent by weight free fatty acids. With soybean oil in particular, a normal-quality crude oil generally contains between about 0.2 and 0.5 percent by weight free fatty acids; however, poorer-quality crude soybean oil may contain free fatty acids in excess of 1 percent by weight. Free fatty acids present in vegetable oils generally comprise the same C
10
to C
22
saturated and unsaturated fatty acids that are present in the triglycerides, as described in detail above.
A high free fatty acid content in a refined vegetable oil generally indicates that the oil was poorly processed or that there has been some triglyceride breakdown after manufacture. Free fatty acids can be valuable materials, however, when properly removed from crude vegetable oil.
Phosphatides
The terms phosphatides or phosphatide concentrates are commonly used to refer to a mixture of phospholipids comprising phosphatidyl derivatives which are present in crude vegetable oil. Such phosphatides also are referred to as gums. After being removed from vegetable oil by treatment with water, phosphatides are often called wet gums or wet lecithin. Upon being dried, phosphatides generally are termed lecithin or commercial lecithin. Crude soybean oil in particular provides the chief source for commercial 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 previously has been thought to match that of the vegetable oil from which the phosphatides 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.
Recovery of Phosphatides From Vegetable Oils
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

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