Hydrogenation free fatty acids

The refining process most commonly used involves treatment with hot aqueous alkaH to convert free fatty acids to soaps, followed by bleaching, usually with hydrogen peroxide, although sodium chlorite, sodium hypochlorite, and ozone have also been used. Other techniques include distillation, steam stripping, neutralization by alkaH, Hquid thermal diffusion, and the use of active adsorbents, eg, charcoal and bentonite, and solvent fractionation... 

As mentioned above, by this technique using a suspended catalyst free fatty acids also can be hydrogenated, provided the reaction is performed in an excess of the corresponding fatty alcohol as solvent [40]. 

Figure D1.6.6 latroscan TLC-FID chromatograms of (A) a lipid fraction enriched with neutral lipids isolated from cod flesh and stored in ice (B) neutral lipids spiked with authentic 1 -0-palmityl-glyceryl ether dipalmitate (GE), coinciding in position with authentic highly unsaturated acids such as 22 6n-3 (C) hydrogenated neutral lipids spiked with GE. The solvent system was 97 3 1 (v/v/v) hexane/diethyl ether/formic acid for 40 min. Abbreviations O, origin SF, solvent front FFA, free fatty acid PL, phospholipids SE, steryl ester ST, free sterol TG, triglyceride. Reproduced from Ohshima et al. (1987) with permission from AOCS Press.

The sample is now ready for analysis using the procedures described above (see Basic-Protocol and Alternate Protocol). Figure D1.6.6 shows chromatograms of cod muscle lipids before and after hydrogenation. Note the single peaks for steryl esters and free fatty acids in panel C compared to the double peaks in panels A and B. 

Chromarod FID peaks of sterols, diglycerides, monoglycerides, and polar lipids are narrower and sharper than peaks of triglycerides and free fatty acids when analyzed using either method described in this unit (see Basic Protocol and Alternate Protocol). Hydrogenation of total lipids (see Support Protocol) results in much sharper and narrower peaks, which in turn substantially improves the resolution between lipid classes. The accuracy and precision in quantitating lipid classes of vegetable oils and animal fats are expected to be better than those from marine lipids. 

With samples containing a wide range of components, such as hydrogenated fats, the column was eluted with solvent A for 13 min, then changed in one step to A-B (75 25), with a gradient to 100% B over 20 min. The free fatty acids were converted into the phenacyl derivatives and, prior to HPLC analysis, were purified by elution from a BOND ELUT NH2 column with hexane-diethyl ether (9 1). 

Selective and Complete Hydrogenation of Vegetable Oils and Free Fatty Acids in Supercritical Fluids... 

In order to overcome the existing problems with the state-of-the-art technology in vegetable oil and free fatty acid hardening, we have investigated hydrogenation reactions in liquid, near-critical, and supercritical C02, as well as C02/propane mixtures with precious-metal fixed-bed catalysts supported on acid-resistant supports. 

Hydrogenation of Vegetable Oi Is and Free Fatty Acids in SCFs 239... 

Fatty acid analysis of a fat is nowadays a relatively routine analytical operation. After methylation of the fat using reaction with boron trifluoride/methanol, boron trichloride/methanol, methanolic hydrogen chloride solution, diazomethane or, if free fatty acids are not present, alkaline catalysts such as sodium methoxide/methanol, the prepared methyl esters are then analysed by GC on a polar column such as CpSil 88, BPX70 or SP2340. The high polarity of the column is necessary to separate the saturated and unsaturated fatty acids fully. The fatty acid composition of a milk fat sample is thus relatively easily obtained, and was therefore one of the first techniques investigated for authentication purposes. 

Canola Oil occurs as a light yellow oil. It is typically obtained by a combination of mechanical expression followed by n-hexane extraction, from the seed of the plant Brassica juncea, Brassica napus, or Brassica rapa (Fam. Cruciferae). The plant varieties are those producing oil-bearing seeds with a low erucic acid (C22 i) content. It is a mixture of triglycerides composed of both saturated and unsaturated fatty acids. It is refined, bleached, and deodorized to substantially remove free fatty acids phospholipids color odor and flavor components and miscellaneous, other non-oil materials. It can be hydrogenated to reduce the level of unsaturated fatty acids for functional purposes in foods. It is a liquid at 0° and above. 

Arsenic, Free Fatty Acids, Iodine Number, Lead, Mercury, Peroxide Value, Saponification Value, and Unsaponifiiable Matter Proceed as directed in the monograph for Menhaden Oil, Hydrogenated. 

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