Solvent extracted oils

Solvent extraction in batch or continuous systems is used to recover most of the residual oil from the presscake. Heptane, hexane, or a mixture of these solvents is used to recover the oil. The solvent-extracted presscake is steam stripped to recover solvent and a residual meal known as castor pomace, containing 1% residual oil. The solvent extracted oil is also processed for solvent recovery (qv). The oil from the extraction procedure is darker than the mechanically pressed oil and has a higher free fatty acid content. It is sometimes referred to as a No. 3 castor oil and is used for blending with higher quaUty oils that are well above No. 1 specifications. 

Oleosomes of seabuckthom fruit flesh were isolated by physical separation techniques and their higher stabilities and antioxidant activities compared to solvent-extracted oil were demonstrated. ... 

Fig. 4 LC-GC-FID chromatograms for typical olive oils. The nearly complete absence of wax esters (esters 40-esters 46) and very low concentrations of steryl esters indicate a high-quality extra virgin oil. The concentration of free stigmasterol is low. C24-26-OH, fatty alcohols. In lampante oils, more wax esters and steryl esters are found. The concentration of stigmasterol increases more than campesterol if the oil was prepared from olives of low quality. Run at the same sensitivity, chromatograms of solvent-extracted oils are completely overloaded. The refined extraction oil was diluted 1 5 before running the chromatogram shown. Wax ester and steryl ester concentrations are very high. (From Ref. 34, p. 626.)...

Vegetable oils including solvent extracted oils... 

Three other GC analyses now used in authentication, largely for olive and other oils which should not be refined or solvent extracted, are the determination of waxes, aliphatic alcohols, triterpene alcohols (uvaol and erythrodiol), and stigmastadiene and other sterol-dehydration products (EEC, 1991). These analyses are used at present not to detect adulteration with other oils, but with solvent-extracted or refined oils. However, it is possible that, with solvent-extracted oils, wax, aliphatic alcohol and terpene alcohol compositions, could prove useful in differentiating or detecting different oils. 

In addition to the above tests, which attempt to detect refining, there are other tests that indicate solvent extraction of the oil. As many oils are solvent extracted, and because solvent extraction usually produces an oil unsuitable for culinary use without refining, then tests for solvent extracted oil are also relevant. These are ... 

Flash and Fire Point. Flash point is the temperature at which the volatile products are evolved at such a rate that they are capable of being ignited but not supporting combustion. At the fire point, the accumulated breakdown products are capable of supporting a flame on their own. A crude cottonseed oil with a fatty acid content of 1.8% was found to have a flash point of 560°F or 293.3°C. Solvent-extracted oils can have a low flash point because of a solvent residue. A flash point analysis would identify this crude oil deficiency to prevent an accidental fire or explosion in an atmosphere that was not explosion proof. Crude vegetable oil shipments received with a flash point below 250°F are rejectable by most trading rules. Figure 1 shows the relationship between free fatty acid content, smoke, flash, and fire points of processed cottonseed and peanut oils. 

Because of the behavior of the solvent, solvent-extracted oil contains more minor components at higher levels than those found in physically extracted oil. This provides the basis for designating pomace oil as a commercial product distinct from virgin oil (obtained only by mechanical means) or refined (lower grade) virgin oil mixed with virgin oil (olive oil, Riviera type). 

Straight Long Chain Alcohols. Linear long-chain alcohols with carbon numbers between C22 and C32 are present in olive oil both free and esterihed (waxes). The components are abundant in the epicarp of the fruit and concentrate in solvent extracted oil. Phytol, probably derived from biodegradation of chlorophyll, is also present along with geranyl (38). 

Cyclic Dihydroxy Compounds. Pentacyclic triterpenes in olive oil include 3p,17p-dihydroxy-12-oleanene (erythrodiol) and its parent compound uvaol, obtained largely from the epicarp and therefore characteristic of solvent extracted oils (42, 65). 

The modem commercial methods of oil extraction from oilseeds include (1) batch hydraulic pressing Oil seeds are expressed by hydraulic pressure to yield oil (2) continuous mechanical pressing Oil seeds are squeezed through a tapering outlet and oil is expressed by the increasing pressure and (3) solvent extraction Oil seeds are extracted with solvent followed by removal of solvent to yield oil. These methods are also employed in the extraction of sesame seeds with some modification. 

Lecithin recovered from solvent-extracted soybean oil had different phospholipid class compositions from those produced by mechanical pressing (198). The percentage of phosphatidylcholine was considerably higher in lecithin recovered from extruded-expelled oU than from solvent-extracted oil. The phosphatidylcholine- and phosphatidylinositol-enriched fractions produced by ethanol extraction of the crude lecithin also showed different functional properties (199). 

Solvent-extracted rapeseed oil has been found to contain the highest level of phosphorus. For this reason, it is common practice to degum solvent-extracted oil or the mixed crude oil from pressing and subsequent solvent-extraction. As the double-zero rapeseed varieties such as canola became available, the applications of rapeseed lecithin have developed positively. Where at first rapeseed lecithin was applied as an emulsifier and energy component in animal feed, the recent concerns about GMO soybean varieties in some parts of the world have increased the market value of the softseed lecithins for food applications (45). The phospholipid composition is similar to soybean lecithin with variations due to crop and processing conditions. The rapeseed phospholipid compositions in Table 12 have been confirmed by recent data, whereas the soybean lecithin composition in... 

Although the dry lecithin can be filtered, many processors prefer to filter the crude oil before degumming (111). Usually, the crude oil is filtered through large plate-and-frame filter presses. If the degumming operation is conducted at a solvent extraction oil mill, then either the miscella, i.e., oil-solvent mixture, or the oil can be filtered. If all of the fines and filter aid are not removed, the dry lecithin will appear cloudy. 

The major lecithin sold domestically in commercial quantities is extracted from soybeans. Com and sunflower seed lecithins are available in limited amounts. Canola is being reviewed as a lecithin source in countries that do not grow significant quantities of soybeans. Lecithins may be added to feeds in cmde or refined forms, remain as residuals in solvent- or mechanical-extracted oilseed meals, be returned to oilseed meals as extracted gums or soapstocks at combined solvent extraction-oil refinery operations, or simply be native to an oilseed fed whole. 

The low temperature in solvent extraction of oilseeds should produce a better oil than oil from the high-temperamre environment of screw-pressing. Solvent, however, extracts some nontriglycerides that are not pressed out by screw-pressing, so screw-press oil is generally of better quality than solvent-extracted oil. Although some animal fats are solvent extracted, most renderers full-press in screw-presses. Solvent extraction of oilseeds, on the other hand, is widely practiced. The section below is based primarily on research conducted with oilseeds. Some of it, however, would also apply to extraction of animal fats. 

At 24 MPa, the calculated amount extracted was 54.4% of the available lipid versus 45% for the experimental amount. At 31 MPa, the values were 58% and 42%. Lee et al. (7) indicated that 57% of the total lipid composition in Skeletonema costatum consisted of acyl glycerols. The calculated yields of 58% and 54% in the present study indicated that almost all of the nonpolar lipids were extracted by CO,. Friedrich et al. (14) claimed that no significant difference was observed in the quantity of total saponiflables between SC CO2 and hexane extracted soybean oils. This is in agreement with the results for SC CO2 extracted and solvent extracted oils of Skeletonema. 

Polyester/wool blends are very popular, the most common blend ratios are 55 45 and 70 30 polyester wool. Polyester rich blends are normally constructed from a texturised polyester fibre warp and 55 45 polyester wool weft yams. The 20 80 polyester/wool is woven from 55 45 warp and a pure weft yam. Worsted polyester/wool blend yams may contain 2.5 - 3% solvent extractable oil, compared with 3.5- 5% for similar all wool yams. The oils have much greater affinity for polyester fibre than wool and after normal piece scouring, the blends contain residual oil content of 0.6 - 1.2% compared with 0.3% for wool. Oxidation of combing oil is influenced by exposure to light which should be avoided before scouring. Addition of surfactant to combing oil improves the scourability of the blend fabric [75]. 

Severe hydrotreatment actually decreases the range of molecular types within the base oil, compared to solvent-extracted base oils. Hydrotreated base oils produced from different crude oils have more consistent properties than solvent-extracted oils made from different crude oils. Since the hydrotreating reactions create high-VI molecules, it is possible to produce base oils from crude oils with an inherently low content of higher VI components and would normally be unsuitable for conventional solvent refining [5]. 

The percentage of PC was considerably higher in lecithin recovered from extruded-expelled oil than from solvent extracted oil, as shown in Figure 2.4. 

For the short-mix process, the oil temperature is raised to 80—90°C (175—195°F) before the addition of the caustic soda. A break between the neutral oil and soapstock takes place immediately, reducing the losses due to emulsification. The contact time between the caustic and oil is reduced to a 30-sec maximum, which helps to reduce the saponification losses. Because it is standard in Europe to degum solvent-extracted oils and to condition the oils with phosphoric acid before refining, the excess caustic treatment can be eliminated or reduced substantially. The oil is finally washed with demineralized water to help remove the traces of soap remaining in the oil and dried with processes similar to the systems used for the long-mix caustic refining process. 

The major phospholipids of . guineensis palm oil expressed as a mole percentage of the total phospholipid are phosphatidylcholines (36%), phos-phatidylethanolamines (24%), phosphatidylinositols (22%), phosphatidylglycerols (9%) and others (9%). The total phospholipid content in crude oil depends on the method of extraction. Values ranging from 20 to 2000 ppm are reported, the lower values are for normal commercially extracted Malaysian oils. The high values are for laboratory-solvent-extracted oils (Goh etal., 1982). 

There is some criticism of the solvent-extracted oil in that it may contain high boiling contaminants present in the original solvent that may amount to between 2% and 20% (this was particularly so when benzene was used as the extracting solvent). Consequently, for aromatherapy, solvent-extracted oils may not be acceptable. However, if hexane is used as the extracting solvent, solvent residues in the essential oil can be reduced to less than 10mgl , which is generally acceptable. 

For the detection of solvent-extracted oils (in which carbon disulphide is used) the Olive Oil Committee of the American Oil Chemists Society recommends the silver benzoate test. 

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