Free-fatty acids

Free fatty acids are major components of many suberin-associated waxes, whereas they are usually minor components of cuticular waxes (245). For example, free fatty acids were the major class of components in the suberin-associated wax from the storage organs of Daucus carota (50% of the wax) and Brassica napobrassica (49%) (116, 219), and the bark waxes of Pinus contorta (43%) (389) and Ailan-thus glandulosa (59%) (76). The major fatty acids in many bark waxes are C20, C22, C24 or a combination of these acids. For example, C22 and C24 were the two dominant components (23% and 34%, respectively) of the free fatty acid fraction that comprised 34% of the wax from the bark of Picea abies (484). In many ana- 

Mediators secondary to free fatty acid release 

There are both teleological and experimental reasons to consider relevant the possibility that mediation (activation of thermogenin) is a consequence of the release of free fatty acids. 

Experimentally, the most simple argument comes from the fact that addition of free fatty acids to isolated cells leads to a thermogenesis which, in all measurable characteristics, is indistinguishable from that observed after norepinephrine stimulation [74,75]. This minimal theory thus states that a rise in the intracellular free fatty acid concentration is probably the only stimulus needed to increase the rate of respiration [75]. 

Although it was initially felt that the free fatty acids acted simply as uncouplers on the mitochondria, this is today considered to be much too simple an explanation. A sketch of the possible interactions of free fatty acids and their derivatives with the mitochondria is shown in Fig. 10.13. Although a series of derivatives are at hand, only extramitochondrial free fatty acids and acyl-CoAs have been more seriously investigated as candidates for the mediator. 

There is no doubt that the addition of free fatty acids to brown fat mitochondria results in a stimulation of respiration. The reason for this response is however not unequivocally clear. As seen in Fig. 10.13, there are at least four possible sites of interaction of free fatty acids with brown fat mitochondria (1) competitively with purine nucleotides on the binding site on thermogenin (2) on another site on thermogenin (3) on another protein site on the membrane or (4) directly with the membrane. 

Most methods for the quantitation of free fatty acids involve chemical derivatiza-tion followed by gas chromatography-mass spectrometry. However, a colorimetric method is available for the quantitation of long-chain (C 10) free fatty acids in plasma, and is based on the color developed by cobalt soaps of free fatty acids dissolved in chloroform.31 

The assay involves four solutions (1) chloroform heptane methanol (4 3 2 by volume) (2) 0.035 M HC1 (3) the salt reagent, consisting of 8 mL of triethanolamine added to 100 mL of an aqueous salt solutions containing 20 g Na2S04, 10 g Li2SC 4, and 4 g Co(NC 3)2.6H2C) and (4) the indicator solution consisting of 20-mg l-nitroso-2-naphthol in 100 mL of 95% ethanol. 

The procedure uses 100-pL samples (heptane blank, standard, or plasma sample) combined with 4.0 mL of chloroform/heptane/methanol and 1.0 mL 0.035 M HC1 in sealed vials. After mixing and centrifugation steps, the upper aqueous methanol phase is discarded, and 2.0 mL of the salt reagent is added and mixed. A second centrifugation step is followed by combining 2.0 mL of the upper phase with 1.0 mL of the indicator solution. After 20-min absorbance is measured at 435 nm. 

Linear calibration curves were obtained for palmitic acid over the 0.10-1.2-pM concentration range, with few interferences. Protein (2% BSA) and many major metabolites such as lactic acid or (3-hydroxybutyrate do not interfere, but some color development is observed for high concentrations of phospholipids such as lecithin. 

Alexander and J. M. Griffiths, Basic Biochemical Methods, Wiley-Liss, New York, 1993, pp. 29-31. 

Unfortunately, MALDI-TOF-MS studies of free fatty acids (FFAs) are hampered by their small molecular weights and the resulting overlap with the peaks of common matrices. According to the present authors best knowledge, four promising approaches have been proposed to date to overcome this problem  

2) Inorganic matrices such as graphite [110] (GALDI-MS) or porous silicon [111] (DIOS-MS) have been also used successfully. Although the achievable sensitivity is rather poor (the main reason why this approach is not very established so far), deprotonated fatty acids could be readily detected in the negative-ion mode. A more detailed survey of this topic is available in Ref. [112]. 

4) Very recently [49], it was shown that l,8-bis(dimethylammo)-naphthalene (OMAN), a superbasic compound (called proton sponge ) with a pfC, of 12.21 [116] is a powerful matrix because it enables the detection of fatly acids (both saturated and moderately unsaturated) in low-picomolar amounts. Therefore, both, 9-AA and DMAN seem more suitable than MTPFPP because all fatty acids can be easily and accurately detected, while the MTPFPP matrix is less suitable for unsaturated fatty acids due to the -tl4amu artifact and the lower achievable sensitivity. Unfortunately, DMAN is not stable under high-vacuum conditions and, thus, there are time-dependent spectral changes. This even holds for the free fatty acids [50]. 

the detection of small molecules remains a challenging aspect of MALDI-MS. 

So far the discussion has dealt with esterified fatty acids and there is only little information concerning the retention of free fatty acids. In experiments in which adipose tissue was labeled by perfusion with tritiated oleic acid, similar loss of lipid occurred, irrespective whether the percent of labeled free fatty acid in the tissue was 27 or 2% (O. Stein et al, 1970b). Strauss and Arabian (1969) have pointed out that the retention of free fatty acid, taken up by segments of intestine incubated at 0°, can be improved by addition of CaCl2 into the fixative, which forms a highly insoluble salt with free fatty acid. 

However, when measuring FFAs in olive oil, consideration is given to the product of the hydrolysis of the triglycerides by free lipolytic enzymes, microorganisms or simply water, in appropriate pH and temperature conditions. Thus the formation of FFAs in oil indicates that the commodity has suffered abnormal damaging conditions. The standard procedure for determining such acids is to dissolve a sample in 50 50 ether-ethanol and titrate the solution with ethanolic potassium hydroxide 0.1 M using phenolphthalein as an indicator. 

M = molecular weight, grams per mole of the acid chosen for expression of the results. 

To avoid any uncertainty attached to the use of a particular acid molecular weight, acid value (AV) may be used AV is the milligrams of potassium hydroxide necessary to neutralize the free acids in one gram of oil, and is calculated as  

V = ml of NaOH or KOH solution used c = concentration in moles per litre of NaOH or KOH solution m = grams of oil 

The usefulness of the test would be enhanced if it were possible to determine the precise chemical nature of the free acids. For instance, by determining the free acids originally present, we should be able to obtain further useful information about both the biosynthesis, and the degradation, of the triacylglycerols. 

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The base lubricant is usually a petroleum oil while the thickener usually consists of a soap or soap mixture. In addition they may contain small amounts of free alkali, free fatty acid, glycerine, anti-oxidant, extreme-pressure agent, graphite or molybdenum disulphide. 

Castile soap is manufactured from olive oil, transparent soap from decolorized fats and liquid green soap from KOH and vegetable oils. Soaps are sometimes superfatted in that they contain some free fatty acid. 

Aldehydes, enals, dienals, ketones, and hydrocarbons, which are responsible for disagreeable odors, generally bok at lower temperatures than fatty acids. Analysis showkig a free fatty acid concentration of less than 0.05% is an kidication that deodorization is sufficientiy complete. Some of the dienals have very low odor thresholds and sensory evaluation of the finished ok is a judicious quaHty assurance step. 

Free Fatty Acid and Saponification Value. High concentrations of free fatty acid are undesirable in cmde triglyceride oils because they... 

Lipids present in the diet may become rancid. When fed at high (>4-6%) levels, Hpids may decrease diet acceptabiUty, increase handling problems, result in poor pellet quaUty, cause diarrhea, reduce feed intake, and decrease fiber digestion in the mmen (5). To alleviate the fiber digestion problem, calcium soaps or prilled free fatty acids have been developed to escape mminal fermentation. These fatty acids then are available for absorption from the small intestine (5). Feeding whole oilseeds also has alleviated some of the problems caused by feeding Hpids. A detailed discussion of Hpid metaboHsm by mminants can be found (16). 

Commercial cmde lecithin is a brown to light yeUow fatty substance with a Hquid to plastic consistency. Its density is 0.97 g/mL (Uquid) and 0.5 g/mL (granule). The color is dependent on its origin, process conditions, and whether it is unbleached, bleached, or filtered. Its consistency is deterrnined 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 aflphatic and aromatic hydrocarbons, including the halogenated hydrocarbons however, it is only partially soluble in aflphatic alcohols (Table 5). Pure phosphatidylcholine is soluble in ethanol. 

Monobasic Acids. The overwhelming majority of moaobasic acids used ia alkyd resias are long-chain fatty acids of aatural occurreace. They may be used ia the form of oil or free fatty acids (see Fats and fatty oils). Free fatty acids are usually available and classified by their origin, viz, soya fatty acids, linseed fatty acids, coconut fatty acids, etc. Fats and oils commonly used ia alkyd resias are givea ia Table 4. 

Fatty Acid Process. When free fatty acids are used instead of oil as the starting component, the alcoholysis step is avoided. AH of the ingredients can therefore be charged into the reactor to start a batch. The reactants are heated together, under agitation and an inert gas blanket, until the desired endpoint is reached. Alkyds prepared by the fatty acid process have narrower molecular weight distribution and give films with better dynamic mechanical properties (34). 

Quaternized esteramines are usually derived from fat or fatty acid that reacts with an alcoholamine to give an intermediate esteramine. The esteramines are then quaternized. A typical reaction scheme for the preparation of a diester quaternary is shown in equation 9 (210), where R is a fatty alkyl group. Reaction occurs at 75—115°C in the presence of sodium methoxide catalyst. Free fatty acids (230) and glycerides (231) can be used in place of the fatty acid methylester. 

Fats and Oils. Fats and oils (6) are traditionally sulfated using concentrated sulfuric acid. These are produced by the sulfation of hydroxyl groups and/or double bonds on the fatty acid portion of the triglyceride. Reactions across a double bond are very fast, whereas sulfation of the hydroxyl group is much slower. Yet 12-hydroxyoleic acid sulfates almost exclusively at the hydroxyl group. The product is generally a complex mixture of sulfated di-and monoglycerides, and even free fatty acids. Other feeds are castor oil, fish oil, tallow, and sperm oil. 

The major components of camauba wax are aHphatic and aromatic esters of long-chain alcohols and acids, with smaller amounts of free fatty acids and alcohols, and resins. Camauba wax is very hard, with a penetration of 2 dmm at 25°C and only 3 dmm at 43.3°C. Camauba also has one of the higher melting points for the natural waxes at 84°C, with a viscosity of 3960 rare]/s at 98.9°C, an acid number of 8, and a saponification number of 80. 

Grease Refining and Fractionation. Lanolin to be used in pharmaceuticals and cosmetics must conform to strict requirements of purity, such as those in the U.S. and British Pharmacopoeias (181,182). These include specifications for the maximum allowable content of free fatty acids, moisture, ash, and free chloride. Lanolin intended for certain dermatological appHcations may have to meet further specifications in relation to free-alcohol and detergent contents (183,184). 

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... 

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