Refined crude oils, fatty acids

Tall oil tal, oi(9)l [part trans. of Gr Talldl, part trans. Swedish tallolja, fr. tall pine + olja oil] n. A generic name for a number of products from the manufacture of wood pulp by the alkah process sulfate or kraft process. To provide some distinction between the various products, designations are often applied in accordance with the process or composition, some of which are cmde tall oil, acid refined tall oil, distilled tall oil, tall oil fatty acids, and tall oil rosin. The following designations for tall oil shall be considered obsolete crude resinous hquid, finn oil, liquid resin, liquid rosin, resin oil, sulfate pitch, sulfate resin, sulfate rosin, Swedish pine oil, Swedish resin, Swedish rosin, Swedish rosin oil, Sylvie oil, talloel, tallol, Swedish oil, fluid resin, and Swedish olein. 

In the early years, most of the crude tall oil was burned for the fuel value and as a method of disposal. But because it was recognized early that CTO was a potential source of fatty acids and rosin, numerous processes including acid refining, solvent extraction, adsorption, selective chemical transformations, and, particularly, distillation were developed to upgrade CTO. Although the distillation processes provided useful products, it was not until 1949 that production of high quality tall oil fatty acids and tall oil rosins by fractional distillation was commercially realized. Virtually all tall oil is now being fractionated. 

It is derived as a by-product from the Kraft (sulfate) process to make - paper pulp. Pinewood is the most common source. After separation of the pulp, the remaining black liquor is concentrated by evaporation, whereby the crude soap is salted out and collected. Acidulation with sulftiric acid and several refining steps gives crude tall oil. Production of one ton of paper pulp yields 30-40 kg of tall oil. Fractional steam-vacuum distillation (200-285 °C 13.3 kPa/lOOmm steam must be present to lower the b.p. and avoid decomposition) separates the oil from the pitch and low-boiling components. The oil is purified by additional fractionation procedures to separate the -+rosin and to produce various grades of purities of tall oil fatty acids (TOFA),... 

Tall oil rosin is a by-product of paper manufacturing. Raw wood chips are digested under heat and pressure with a mixture of sodium hydroxide and sodium sulfide. Soluble sodium salts of lignin, rosin, and fatty acids are formed, which are removed from the wood pulp as a dark solution. The soaps of the rosin and fatty acids float to the top of the mixture, where they are skimmed off and treated with sulfuric acid to free the rosin and fatty acids. This mixture, known as crude tall oil (CTO), is refined further to remove color and odor bodies fractional distillation separates the tall oil rosin acids from the fatty acids (see Tall oil). 

Commercial crude lecithin is a hrown to light yellow fatly substance with a liquid to plastic consistency. Its density is 0.97 g/niL (liquid) and 0.5 g/mL (granule). The color is dependent on its origin, process conditions, and whether it is unbleached, bleached, or Altered. Its consistency is determined chiefly by its oil. free fatty acid, and moisture content. Properly refined lecithin has practically no odor and has a bland taste. It is soluble in aliphatic and aromatic hydrocarbons, including the halogenated hydrocarbons however, it is only partially soluble in aliphatic alcohols. Pure phosphatidylcholine is soluble in ethanol,... 

Hydrolyzed vegetable oil (HVO) or acid oil is a by-product of alkali refining of crude corn oil, and is obtained by acidulating alkaline soapstock. HVO must contain at least 92% total fatty acids. It is used to control dust and as an energy source in beef and poultry rations. 

Free Fatty Acids in Crude and Refined Fats and Oils (FFA) (Ca 5a-40) determines FFA, as oleic acid, by ethanolic sodium hydroxide titration. 

Refining Loss, Vegetable Oils, Crude (Ca 9a-52) determines the loss of free fatty acids and impurities when crude oils are refined under specified procedures. Residual Lint (Aa 7-55) determines the lint content of cottonseed by fuming (digesting) with hydrochloric acid. 

Coconut Oil (Unhydrogenated) occurs as a viscous, white to light yellow-tan liquid. It is obtained from the kernel of the fruit of the coconut palm Cocos nucifera (Fam. Palmae). The crude oil obtained by mechanically pressing dried coconut meat (copra) is refined, bleached, and deodorized to substantially remove free fatty acids, phospholipids, color, odor and flavor components, and other non-oil materials. Compared with many natural fats, Coconut Oil (Unhydrogenated) has an abrupt melting range, changing from a rather firm, plastic solid at about 21° or below to a liquid at about 21°. 

Acid value (AV). This value is important for determination of free fatty acids (FFA) in crude and refined oils and fats. It is the number of milligrams of KOH needed to neutralize the organic acids present in 1 g of oil or fat. FFA is calculated as free oleic acid and reported as a percentage. The AV is determined by multipl5dng percent FFA with a factor of 1.99. 

Lipolysis. Free fatty acids (FFA) result from lipolysis (hydrolysis) of oils and fats. This is determined by the FFA or acid value. The crude oils and animal fats usually have a FFA content exceeding 1 percent. The FFA content is lowered to less than 0.1 percent by the refining of oil or fat. 

Although it is convenient to categorize oils by their fatty acid composition, it must be remembered that this is not the only index of their nutritional value or of their oxidative stability. Attention must also be given to the minor components in the crude oil and to those remaining after refining (see Section 3). 

Refining of crude fats and oils involves a series of steps for the removal of impurities from the glycerides to make the product suitable for human consumption and improve product shelf life. The impurities are fatty acids, phosphatides, metal ions, color bodies, oxidation products, solid paricles, and volatiles that include objectionable odors. Crude coconut oil is refined by any of the following methods (1) chemical refining (batch or continuous) and (2) physical refining. The comparative performance of both methods is summarized in Figure 4. 

The main feature in physical refining of crude oils is the application of steam distillation to remove the free fatty acids and volatile components from the oil. The technical feasibility of physical refining depends largely on the pretreatment stages for the removal of phosphatides, color bodies, metal ions, and nonvolatile impurities. Without an effective pretreatment, steam refining may fail to produce an oil of color and stability characteristics comparable to the classically refined product (23). 

Two methods, namely physical rehning and chemical rehning, are available for refining crude palm oil. They differ basically in the manner in which the free fatty acids are removed. Physical rehning has become the major processing route because of its cost effectiveness, efficiency, and simple effiuent treatment (39). Both processes are able to produce rehned, bleached, and deodorized (RBD) palm oil of desirable quality and stability suitable for edible purposes (40). The unit operations involved in these two processes and the components removed are shown in Figure 12 and Table 31, respectively. 

Refining of Other Palm Products. Beside crude palm oil, crude palm olein, crude palm stearin, cmde kernel oil, crude palm kernel olein, and crude palm kernel stearin can also be refined by either chemical or physical processes described before. The basic unit operations and processing conditions for crude palm olein and stearin are similar to those of palm oil. However, in refining palm kernel products, due to the virtual absence of carotenoids, the earth dosage required in the bleaching stage is lower, usually less than 1.0%. Furthermore, due to the presence of shorter chain (C8-C14) fatty acids, the deodorization temperature required is about 230-250°C. Typical achievable quality of RBD/NBD palm kernel oil is given in Table 34. 

By-products. Chemical Refining. The neutralization of free fatty acid in the crude pahn oil with caustic soda results in the formation of soapstock, which is treated with dilute sulfuric acid of pH 2.0-3.5 at 110-130°C for 30 min. A by-product called palm acid oil is then separated from the aqueous phase by centrifugation followed by hot-water washing. It consists mainly of free fatty acids, neutral oil, and partial glycerides. A small amount of unsaponifiable matter is also present. Characteristics and properties of palm acid oil (derived from chemical refining of crude pahn oil, stearin, and olein) are given in Table 35 (55). 

Physical Refining. The by-product in the physical refining of crude palm oil is the pahn fatty acid distillate (PFAD). It is obtained as a condensate of the volatile matters carried over from the deodorizer by the action of the stripping steam. It consists of 80-90% of free fatty acid. It has often been used as a raw material for soap making, feed compounding, and oleochemical feedstock. An important and valuable constituent of PFAD is vitamin E in the form of tocopherols and... 

General. Pahn oil is one of the most stable vegetable oils, and this can be attributed to the presence of natural antioxidants, and also to the balanced ratio of saturated to unsaturated fatty acids. Nevertheless palm oil, whether crude or refined, is still susceptible to quality deteriorations. Stringent preventive measures are necessary to ensure the production of refined pahn oil products of superior quality and acceptability. 

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