OLEIC ACID, FROM TALL OIL FATTY ACIDS

Description

Tall oil (“tall” is Swedish for “pine”) is basically the sap of the pine tree. The tall oil of commerce, however, is a by-product derived from the waste liquors of the pinewood pulp mills in the kraft or sulfate process of paper manufacture. It consists mainly of a mixture of fatty and resin (or rosin) acids, and varies in composition and properties depending upon the source of the wood and the processing methods used. The resin acids and fatty acids (tall oil) are removed from the wood and converted to soaps by the highly alkaline pulping chemicals. Crude tall oil, recovered when the skimmings are acidified, is separated through distillation into resin and fatty acid fractions. A large portion of the resin acids is used in the paper industry, and most of the fatty acids in the paint and detergent industries.
Crude tall oil is composed of two major fractions, tall oil resin acids and tall oil fatty acids, and a minor fraction consisting of a mixture of unsaponifiable or “neutral” substances. The bulk of the resin acids, comprising about 42 percent of tall oil, consists of diterpenoid monocarboxylic derivatives of alkylated hydrophenanthrenes of the abietic and pimaric acid types. A typical analysis of tall oil resin shows an abietic acid content of 34 percent; dehydroabietic acid, 24 percent; palustdc acid, 9 percent; isopimadc acid, 6 percent; dihydroabietic acid, 5 percent; pimaric acid, 5 percent; and neoabietic acid, 5 percent.
The fatty acid fraction constitutes about 51 percent of the tall oil. Oleic and linoleic acids, in approximately equal percentages, comprise about 80 percent of this fraction, and cis-5,9,12-octadecatrienoic acid accounts for about 10 percent. The remaining 10 percent consists of small amounts of various acids including myristic, palmitic, stearic, palmitoleic, linolenic, and a number of saturated and mono-, di-, and triunsaturated acids, ranging from C17 (straight and branched chain) to C20 (straight chain). The locations of the double bonds in the octadecatrienoic and eicosatrienoic acids of tall oil differ from those of the seed fats. The characteristic compounds of the former are cis-5,9,12-octadecatrienoic and cis-5,11,14- eicosatrienoic acid.
The unsaponifiable fraction accounts for about 7 percent of tall oil. It consists mainly of hydrocarbons, sterols, including α- and (β-sitosterol and stigmasterol, and some of the higher alcohols. Sitosterol, identified by several workers as largely p-sitosterol, makes up from 70 to 75 percent of this fraction. This sterol has been of medical interest because of its reported anti-cholesterolemic properties.
Tall oil fractions, e.g., distilled tall oils and tall oil light ends ranging in color from pale to dark, are available on the market under a number of trade names; composition and properties vary depending on conditions of manufacture.
Tall oil can also be used as a defoaming agent in the manufacture of paper and paperboard intended for use in packaging, transporting, or holding food and as a substance generally recognized as safe for use as a component of adhesives. Constituents or fractions of tall oil, e.g., oleic and linoleic acids, tall oil rosin and dark tall oil rosin, tall oil pitch, and tall oil soaps, may be used in foods, as defined in these regulations, or in the manufacture of articles or components of articles intended for use in producing, manufacturing, packing, processing, preparing, treating, packaging, transporting, or holding food.