Organic compounds -- part of the class 532-570 series – Organic compounds – Fatty compounds having an acid moiety which contains the...
Reexamination Certificate
1999-05-03
2001-05-08
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...
C554S012000, C426S601000, C426S653000
Reexamination Certificate
active
06229033
ABSTRACT:
FIELD OF THE INVENTION
This invention concerns the fractionation of soybean oils and, in particular, high stearic soybean oils to make a fat product useful in confectionary applications. Also of concern is the fractionation of high stearic, high oleic soybean oils to make a fat product useful in confectionary applications and liquid, high stability oils.
BACKGROUND OF THE INVENTION
Fats and oils play a major role in human nutrition and are recognized as essential nutrients in both human and animal diets. Nutritional concerns have led to the replacement of animal-fat shortenings with vegetable oils as the major source of lipids in human diets. The most commonly used vegetable oil worldwide is soybean oil. Over 19 million metric tons of soybean oil were consumed in 1995 alone. The use of soybean oil in the United States is extremely popular. In fact, over 80% of the vegetable oils consumed in the United States are soybean oils which are used in margarines, shortenings, salad and cooking oils, and commercial frying oils. About half of the soybean oil consumed is in the form of margarines or shortenings and frying oils.
The specific performance and health attributes of edible oils in general are determined largely by their fatty acid composition. Soybean oil is composed primarily of palmitic (C16:0), stearic (C18:0), oleic (C18:1), linoleic (C18:2) and linolenic (C18:3) acids and, in that regard, is similar to the other most commonly used vegetable oils including palm, sunflower, canola, cottonseed, peanut, coconut, olive and palm kernel.
By comparison, soybean oil contains relatively high levels of both linoleic and linolenic acid relative to some other vegetable oils. These fatty acids are more prone to oxidation than saturated and monounsaturated fatty acids. Without modification, soybean oil is relatively unstable to oxidation reactions and its use is limited to applications that do not require a high degree of stability. Under extended use, oxidized soybean oil develops off flavors and undergoes physical changes such as increased viscosity and foaming.
Several methods are available to increase the stability of soybean oil. One commonly used method is catalytic hydrogenation, a process that reduces the number of double bonds and raises the melting point of the fat with the aid of a catalyst such as nickel. Specifically, catalytic hydrogenation reduces the level of polyunsaturated fatty acids, primarily linoleic (C18:2) and linolenic (C18:3) acids, and increases oleic (C18:1) and stearic (C18:0) acids. This results in a stable oil suitable for food frying and specialized high stability oil applications due to the reduction of the unsaturated fatty acid content. Also, the physical properties of the oil are changed because the fatty acid modifications increase the melting point resulting in a semi-liquid or solid fat at room temperature. A large percentage of the soybean oil consumed annually is partially hydrogenated soybean oil.
In general, soybean oil is produced using a series of steps involving the extraction and purification of an edible oil product from the oil bearing seed. Soybean oils and soybean byproducts are produced using the generalized steps shown in the diagram below.
Impurities Removed/
Process
Byproducts Obtained
Soybean Seed
↓
Oil Extraction
→
Meal
↓
Degumming
→
Lecithin
↓
Alkali or Physical Refining
→
Gums, Free Fatty Acids, Pigments
↓
Water Washing
→
Soap
↓
Bleaching
→
Color, Soap, Metal
↓
(Hydrogenation)
↓
(Winterization)
→
Stearine
↓
Deoderization
→
FFA, Tocopherols, Sterols, Volatiles
↓
Oil Products
Soybean seeds are cleaned, tempered, dehulled, and flaked which increases the efficiency of oil extraction. Oil extraction is usually accomplished by solvent (hexane) extraction but can also be achieved by a combination of physical pressure and/or solvent extraction. The resulting oil is called crude oil. The crude oil may be degummed by hydrating phospholipids and other polar and neutral lipid complexes that facilitate their separation from the nonhydrating, triglyceride fraction (soybean oil). The resulting lecithin gums may be further processed to make commercially important lecithin products used in a variety of food and industrial products as emulsification and release (antisticking) agents. Degummed oil may be further refined for the removal of impurities; primarily free fatty acids, pigments, and residual gums. Refining is accomplished by the addition of a caustic agent that reacts with free fatty acid to form soap and hydrates phosphatides and proteins in the crude oil. Water is used to wash out traces of soap formed during refining. The soapstock byproduct may be used directly in animal feeds or acidulated to recover the free fatty acids. Color is removed through adsorption with a bleaching earth that removes most of the chlorophyll and carotenoid compounds. The refined oil can be hydrogenated resulting in fats with various melting properties and textures. Winterization (fractionation) may be used to remove stearine from the hydrogenated oil through crystallization under carefully controlled cooling conditions. Deodorization which is principally steam distillation under vacuum, is the last step and is designed to remove compounds which impart odor or flavor to the oil. Other valuable byproducts such as tocopherols and sterols may be removed during the deodorization process. Deodorized distillate containing these byproducts may be sold for production of natural vitamin E and other high-value pharmaceutical products. Refined, bleached, (hydrogenated, fractionated) and deodorized oils and fats may be packaged and sold directly or further processed into more specialized products. A more detailed reference to soybean seed processing, soybean oil production and byproduct utilization can be found in Erickson, 1995, Practical Handbook of Soybean Processing and Utilization, The American Oil Chemists' Society and United Soybean Board.
Soybean oil is liquid at room temperature because it is relatively low in saturated fatty acids when compared with oils such as coconut, palm, palm kernel and cocoa butter. Many processed fats, including spreads, confectionary fats, hard butters, margarines, baking shortenings, etc., require varying degrees of solidity at room temperature and can only be produced from soybean oil through alteration of its physical properties. This is most commonly achieved through catalytic hydrogenation.
Hydrogenation is a chemical reaction in which hydrogen is added to the unsaturated fatty acid double bonds with the aid of a catalyst such as nickel. High oleic soybean oil contains unsaturated oleic, linoleic, and linolenic fatty acids and each of these can be hydrogenated. Hydrogenation has two primary effects. First, the oxidative stability of the oil is increased as a result of the reduction of the unsaturated fatty acid content. Second, the physical properties of the oil are changed because the fatty acid modifications increase the melting point resulting in a semi-liquid or solid fat at room temperature.
There are many variables which affect the hydrogenation reaction which in turn alter the composition of the final product. Operating conditions including pressure, temperature, catalyst type and concentration, agitation and reactor design are among the more important parameters which can be controlled. Selective hydrogenation conditions can be used to hydrogenate the more unsaturated fatty acids in preference to the less unsaturated ones. Very light or brush hydrogenation is often employed to increase stability of liquid oils. Further hydrogenation converts a liquid oil to a physically solid fat. The degree of hydrogenation depends on the desired performance and melting characteristics designed for the particular end product. Liquid shortenings, used in the manufacture of baking products, solid fa
Carr Deborah D.
E. I. Du Pont de Nemours and Company
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