Medium-chain saturated fatty acids

Fats and oils may be synthesized in enantiomerically pure forms in the laboratory (30) or derived from vegetable sources (mainly from nuts, beans, and seeds), animal depot fats, fish, or marine mammals. Oils obtained from other sources differ markedly in their fatty acid distribution. Table 2 shows compositions for a wide variety of oils. One variation in composition is the chain length of the fatty acid. Butterfat, for example, has a fairly high concentration of short- and medium-chain saturated fatty acids. Oils derived from cuphea are also a rich source of capric acid which is considered to be medium in chain length (32). Palm kernel and coconut oils are known as lauric oils because of their high content of C-12 saturated fatty acid (lauric acid). Rapeseed oil, on the other hand, has a fairly high concentration of long-chain (C-20 and C-22) fatty acids. 

In the Nurses Health Study (Hu et ah, 1997), the dietary intake of short- and medium-chained saturated fatty acids (4 0-10 0) was not significantly associated with CHD (but other saturated fatty acids were). In an intervention study a higher intake of medium-chained triglycerides was found to significantly decrease total adipose tissue, subcutaneous adipose tissue, and upper-body adipose tissue stores in men compared to longer chained triglyceride consumption (St-Onge, 2005). 

It is now known that not all saturated fatty acids are equally hypercholesterole-mic. For example, medium-chain saturated fatty acids of carbon length 8-10, as well as stearic acid (18 0), have little or no effect on serum cholesterol concentrations. In contrast, evidence indicates that palmitic acid (16 0), the principle fatty acid in most diets, can increase serum cholesterol concentrations in humans. However, in normocholesterolemic humans, dietary palmitic and oleic acids have been shown to exert similar effects on serum cholesterol, suggesting that only humans or animal species sensitive to dietary cholesterol and selected fats ( hyperresponders ) may exhibit significant changes in semm cholesterol in response to dietary fat intake. Myristic acid (14 0) and, to a lesser extent, lauric acid (12 0), which are relatively high in coconut oil, both can raise serum cholesterol and LDL-cholesterol levels. Overall, it is not clear why humans respond so differently to cholesterol or... 

The composition of the lauric oils, with a high content of short and medium chain saturated fatty acids, makes them especially suitable for use in confectionery, as coating and filling fats, and in vegetable oil-based dairy products such as filled milk, whipped cream, coffee whitener. The lauric oils are also of importance in the oleochemicals industry, and they are unique among food oils in that about one half of their use is in oleochemicals. Analyses of the various kernel oils listed in the tables show differences in the proportions of the short- and medium-chain fatty acids. Some of the oils would be of particular value where a special application is available for a fatty acid that is only a minor component of coconut or palm kernel oil. 

Thioesterase activity has also been targeted as a means of producing medium-chain saturated fatty acids (MCFA) in BOS. MCFA, such as lauric acid (12 0), are widely used for industrial applications, including cosmetics and surfactants, as well as for certain food applications such as confectionary. In most BOS, including canola, the endogenous acyl-ACP thioesterase exhibits a preference for 18-carbon FAs. Production of MCFA required the introduction of a thioesterase with appropriate medium-chain specificity, such as the 12 0 ACP-thioesterase from the California bay laurel (Umbellularia californica) (Voelker et al., 1996). Although the expression of this enzyme in canola resulted in a relatively high accumulation of lauric acid. 

Coconut oil is a major source of medium chain saturated fatty acids used in the lipo chemical industry. Their fatty acid derivatives also provide good solubility of detergents in water and good foaming action, and these are mainly used in the fields of plastics, cosmetics and creams. 

The saturated fatty acids that are present in significant quantities in milk fat are molecules with un-branched hydrocarbon chains, which vary in length from 4 to 18 carbon atoms. These fatty acids account for approximately 70 to 75% of the total fatty acids. The most important saturated fatty acid from a quantitative viewpoint is 16 0, which accounts for about 25 to 30% of the total, while two other fatty acids, 14 0 and 18 0 have values in the region 10 to 13% (Table 1.2). The amounts of the short-chain fatty acids, 4 0 and 6 0, are reasonably high when their proportions are expressed as molar percentages (approximately 10 and 5%, respectively—Table 1.2) appreciable amounts of medium-chain length fatty acids (Cs to C12) are also present. 

Figure 8.3. Fatty acid composition of anhydrous milk fat and selected milk fat fractions grouped in short chain, medium chain and long chain saturated fatty acids and unsaturated fatty acids. For definition of fractions, see Figure 8.1. The numbers in the bars give the percentage of the group of fatty acids. Data from Deffense (1987, Table 3).

The most common dietary fatty acids are the saturated long-chain fatty acids palmitate (C16) and stearate (C18), the monounsaturated fatty acid oleate (C18 l), and the polyunsaturated essential fatty acid, linoleate (C18 2) (To review fatty acid nomenclature, consult Chapter 5). Animal fat contains principally saturated and monounsaturated long-chain fatty acids, whereas vegetable oils contain linoleate and some longer-chain and polyunsaturated fatty acids. They also contain smaller amounts of branched-chain and odd-chain-length fatty acids. Medium-chain-length fatty acids are present principally in dairy fat (e.g., milk and butter), maternal milk, and vegetable oils. 

Palm kernel ell (palm seed oil or fat). An oil obtained from the seeds (kernels) of the palm oil tree (Elaeis guineensis) and related palm species, the fruit pulp of the palm oil tree furnishes palm oil. The worldwide production of P. in 1993 amounted to 1.8 million tons. Mp. 23-30°C. On account of its high contents of esterifled, saturated fatty acids of medium chain length, e. g. lauric acid (ca. 50%) and myristic acid (ca. 15%), P. resembles coconut fat (so-called lauric fats and oils that are rich in lauric acid and other medium-chain length fatty acids) other components ca-proic acid (hexanoic acid) (5%), caprylic acid (octa-noic acid) (3%), palmitic acid (6-9%), stearic acid (2-3%), oils (10-18%), and linoleic acid (1-3%). For the composition of the seed oils of other palm species, see Lir.. ... 

Cohen, L.A. (1987) Differing effects of high-fat diets rich in polyunsaturated, monounsa-turated or medium chain saturated fatty adds on rat mammary tumor promotion, in Proceedings of the AOCS Short Course on Polyunsaturated Fatty Acids and Eicosanoids, ed. W.E.M. Lands, American Oil Chemists Sodety, Champaign, IL, pp. 241-247. 

Carnielli, V.R., Sulkers, EJ., Moretti, C., Wattimena, J.L., van Goudoever, J.B., Degenhart, H.J., Zacchello, E, and Sauer, R.J. Conversion of octanoic acid into long-chain saturated fatty acids in premature infants fed a formula containing medium-chain triglycerides. Metabolism 43, 1287-1292, 1994. 

Coconut oil cake is a waste by-product obtained after the oil extraction fium dried coconut. The major compounds fium the coconut oil cake are short chain saturated fatty acids, which were proposed to be used as a carbon substrate somce in solid-state fermentation (SSF) for enzymes biosynthesis. This approach in which the coconut oil cake represents a cheap way for the bioproducts synthesis is a new one and was adopted in the last years. The first report on enzymes synthesis using coconut oil cake was published by Ramachandran and coworkers, in 2004. The researchers optimized the production of a-amylase using a fungal culture of Aspergillus oryzae strain in SSF cultivation system on a medium based on raw coconut oil cake and it was obtained an a-amylase activity of 1372 U/g dw, in 24 h. Eight... 

It is important to bear in mind when discussing the effect of dairy fat in association to heart disease that dairy products contain many different saturated fatty acids that do not exert the same biological response in terms of, for example, cholesterol levels. The saturated fatty acids in milk fat include shorter and medium chain fatty acids (2 0-10 0), lauric acid (12 0), myristic acid (14 0), palmitic acid (16 0), and stearic acid (18 0). Other fatty acids in milk fat are oleic acid (18 1) and linoleic acid (18 2n-6) as indicated in Table 1.2. 

Since then, there have been numerous studies that investigated the effect of different types and amounts of fat, individual fatty acids and other dietary components on plasma cholesterol level. It is now realized that all saturated fatty acids do not elevate plasma cholesterol levels to the same extent. The short-chain fatty acids, butyric (C4 o), caproic (C6 o), caprylic (Cs o) the medium-chain capric (Cio o) and stearic (Ci8 o) acids,... 

Medium-chain fatty acids are saturated fatty acids because of the relatively shorter hydrocarbon chain, which does not facilitate unsaturation. The safety of medium-chain triacylglycerol (MCTs) in dietary oil has been debated, and associated effects on cholesterol metabolism remain unclear. Although some studies have shown that... 

Marine mammal oils or their co3 concentrates can also be modified for different applications. Modifications include the changing of the fatty acid composition and/ or their location in the glycerol backbone. Structured lipids containing both 0)3 long-chain PUFAs, possibly from seal blubber oil, or their co3 concentrates, and medium-chain fatty acids (MCFAs), which are saturated fatty acids with 6-12... 

---