Fatty acid esters, extraction

Provitamin D. Provitamin is made from cholesterol, and its commercial production begias with the isolation of cholesterol from one of its natural sources. Cholesterol occurs ia many animals, and is generally extracted from wool grease obtained by washing wool after it is sheared from sheep. This grease is a mixture of fatty-acid esters, which contain ca 15 wt % cholesterol. The alcohol fraction is obtained after saponification, and the cholesterol is separated, usually by complexation with 2iac chloride, followed by decomplexation and crystallisation. Cholesterol can also be extracted from the spiaal cords and brains of animals, especially catde, and from fish oils. 

In a typical example of reactive extraction a fatty acid ester was easily formed by adding a small amount of an alcohol to a fatty acid metal salt and extracting at 315 °C [647]. This method was applied to PP/calcium stearate and PP/zinc stearate containing pellets the presence of the fatty acid metal salts was confirmed by GC-MS. 

Chromatographic methods were developed for the systematic determination of five classes of additives in PE for food packaging [170]. In Soxhlet extractions phenolic AOs and acid amides were determined by HPLC and CGC, respectively. Thiodipropionic acid esters were determined by HRGC as higher alcohols obtained after saponification of the extracts with KOH. Glycerol fatty acid esters and stearates were determined... 

On-line SFE-pSFC-FTIR was used to identify extractable components (additives and monomers) from a variety of nylons [392]. SFE-SFC-FID with 100% C02 and methanol-modified scC02 were used to quantitate the amount of residual caprolactam in a PA6/PA6.6 copolymer. Similarly, the more permeable PS showed various additives (Irganox 1076, phosphite AO, stearic acid - ex Zn-stearate - and mineral oil as a melt flow controller) and low-MW linear and cyclic oligomers in relatively mild SCF extraction conditions [392]. Also, antioxidants in PE have been analysed by means of coupling of SFE-SFC with IR detection [121]. Yang [393] has described SFE-SFC-FTIR for the analysis of polar compounds deposited on polymeric matrices, whereas Ikushima et al. [394] monitored the extraction of higher fatty acid esters. Despite the expectations, SFE-SFC-FTIR hyphenation in on-line additive analysis of polymers has not found widespread industrial use. While applications of SFC-FTIR and SFC-MS to the analysis of additives in polymeric matrices are not abundant, these techniques find wide application in the analysis of food and natural product components [395]. 

The transesterification of sucrose has been performed with a fatty acid ester of a volatile alcohol in the presence of an alkaline catalyst in a dipolar, aprotic solvent.142 The reaction of sucrose (293 mmoles) with methyl dodecanoate (293 mmoles) in A/,N-dimethylformamide in the presence of sodium methoxide in a pressure bomb for 8 h at 130° gave, after solvent extraction and crystallization, sucrose mono(dodecanoate) (m.p. 72-80° [a]D+52°) in 50% yield.142 Commercialization of these sucrose esters has so far been limited, in part because of the use of expensive solvents, and, in part, because solvent remaining in the product makes it unsuitable for use as a food emulsifier. In view of this situation, methods have been developed in which the use of toxic and expensive solvents has been avoided. 

An alternative procedure involves the release of the fatty acids by alkaline hydrolysis (saponification) by refluxing the extracted sample with dilute alcoholic potassium hydroxide for 1 h. After cooling, adding water and acidifying, the fatty acids are extracted into diethyl ether. The methyl esters can then be prepared by treatment with diazomethane, which may also be used directly on free fatty acids. Saponification is less satisfactory, because it is a lengthy procedure and often results in the loss of lipid components. 

The formation of two aqueous phases can be exploited in the recovery of proteins using liquid-liquid extraction techniques. Many factors contribute to the distribution of a protein between the two phases. Smaller solutes, such as amino acids, partition almost equally between the two phases, whereas larger proteins are more unevenly distributed. This effect becomes more pronounced as protein size increases. Increasing the polymer molecular weight in one phase decreases partitioning of the protein to that phase. The variation in surface properties between different proteins can be exploited to improve selectivity and yield. The use of more hydrophobic polymer systems, such as fatty acid esters of PEG added to the PEG phase, favors the distribution of more hydrophobic proteins to this phase. In Fig. 10.13, partition coefficients for several proteins in a dextran-PEG system are given [27]. 

Free Fatty Acids. In our gas chromatographic analyses of brandy extracts prepared for fatty acid ester measurements, free fatty acids also emerged as broad tailing peaks at the end of the programmed temperature run. Free fatty acids have been identified as components of various... 

In general, RP-HPLC has been applied successfully to the qualitative and quantitative estimation of carotenes (64), xanthophylls, cis- and trans-carotenoids (54,60), and carotenoid fatty acid esters (53,65). Figure 5 shows an HPLC separation of (A) paprika extract, containing carotenoid esters, and (B) saponified paprika extract, containing the corresponding carotenoids (74a). 

Our present efforts are being devoted to studying pea lipides in situ, in the hope of determining whether hormone activation by lipide substances is a natural method of growth regulation. Gas chromatography has already confirmed that our original active pea extract is a mixture of conventional fatty acid esters. 

The third category is the basis of many commonly used methods. In general, the steps in this category are solvent extraction to remove the lipid fraction, saponification, methylation to fatty acid esters, separation using chromatographic columns and GC analysis. Martin-Hemandez... 

Table 4.10. Fatty acids of Calliobothrium verticillatum and of its host, the dogfish Mustelus canis. Samples were saponified, their fatty acids were extracted and methylated, and the fatty acid methyl esters were characterised and quantified by gas-liquid chromatography. (Data from...

Wax Content. Olive oil fatty acid esters of straight chain alcohols (wax esters present in solvent extracted olive-pomace oil are isolated by column chromatography on silica gel (LC) and quantitated by GLC to determine if olive-pomace oil is present in olive oil (78). LC separation of the wax esters can be replaced with HPLC to automate the separation step and improve rehability and repeatabihty (79). Limits for content of C40 + C42 + C44 + C46 wax esters (mg/kg) are as follows (12) ... 

The preparation of high-purity tocopherols and phytosterols involves steps such as molecular distillation, adduct formation, liquid-liquid extraction, supercritical fluid extraction, saponification, and chromatography (175). The extraction of tocopherols from soybean oil deodorizer distillate by urea inclusion and saponification of free fatty acids resulted in good recovery of tocopherols (208). To improve the separation of sterols and tocopherols, Shimada et al. (209) used a lipase to esterify sterols with free fatty acids. Then the steryl esters and tocopherols were separated better by molecular distillation. Chang et al. (210) used supercritical fluid CO2 extraction to recover tocopherols and sterols from soybean oil deodorizer distillate. A patent by Sumner et al. (211) advocated treatment of the distillate with methanol to converted free fatty acids and other fatty acid esters to methyl esters that can then be removed by a stripping operation. Then separation of sterols and tocopherols could be carried out by molecular distillation. 

The raw material for CLA production must be a material that is rich in linoleic acid. This product could be in the triacylglycerol form, fatty acids or fatty acid esters. The concentration of CLA in the final product is directly dependent on the level of linoleic acid in the starting material. The highest level of linoleic acid available from botanical sources is not available in commercial products. Extraction and refining equipment would be required to obtain oils with the highest linoleic acid levels. Table 1 lists the commercial and noncommercial sources of oil and fatty acids that are known to be rich in linoleic acid and their availability as TAGs and fatty acids. 

In the DOD, phytosterols are present in both the free and esterified forms with fatty acids. Therefore, the first step in the extraction of phytosterols is conversion of phytosterol fatty esters into free phytosterols. This is achieved either by hydrolysis or trani-esterification. Hydrolysis could be carried out under strong basic conditions (saponification with further acidulation), under strong acidic conditions, or under chemical or enzyme (specific or nonspecific) catalyzation. Re-esterification of phytosterols occurs during methyl ester distillation as a result of the high temperatures involved therefore, a further trani-esterification step for free sterols is required. Esterification of phytosterols or trani-esterification of sterol fatty acid esters is the second step in this process. Methanol is the most commonly used alcohol, and it leads to methyl esters, which are characterized by a higher volatility, however, other Ci to C4 alcohols may also be used. Esterification and trans-esterification of fatty acids or phytosterols can be catalyzed by metal alcoholates, or hydroxide, by organic catalysts, or by enzymes (Table 7). 

Supercritical CO2 column fractionation has also been investigated for the production of squalene concentrates from olive oil deodorizer distillates (56, 87). Bon-dioli et al. (87) used saponification and esterification steps to convert the FFA and fatty acid esters to triacylglycerols in order to improve squalene separation prior to countercurrent continuous fractionation. The highest squalene purity and extraction yield was achieved at 15 MPa and 313 K, using a temperature gradient of 303-323 K along the column to improve the squalene purity and yield. Ruivo et al. 

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