Fatty acids composition, temperature

Chapman and co-workers (1966, 1967) studied the spectra of films of pure phospholipids, including phosphatidylcholine and phosphatidylethanolamine. Phospholipid spectra were extremely variable, changing markedly with temperature and method of sample preparation. In particular, the gel-to-fluid thermotropic transition causes the resultant vibrational bands to be smeared out and to be devoid of fine structure (Fig. 9.8). Wallach etal (1978) studied multibilayer films of pure phospholipids and phospholipid mixtures as a function of fatty acid composition, temperature and degree of hydration. Table 9.3 summarizes the main band frequencies observed in these studies. 

Com oil s flavor, color, stabiHty, retained clarity at refrigerator temperatures, polyunsaturated fatty acid composition, and vitamin E content make it a premium vegetable oil. The major uses are frying or salad appHcations (50%) and margarine formulations (35%). 

Membranes are composed of phospholipids and proteins. The fatty acid composition of the phospholipids in a membrane influences how it is affected by the cold. In general, as the temperature of a cell is lowered the lipids in the membrane bilayer undergo a phase transition from a liquid crystalline (fluid) state to a gel (more solid) state. The temperature at which this transition takes place is very narrow for phospholipids composed of a simple mixture of fatty acids, but is quite broad for the phospholipids in cellular membranes. It is usually implied from various methods... 

Fats are solid triacylglycerols, oils are liquid triacylglycerols it is the fatty acid composition of the triacylglycerol that determines its physical properties. Triacylglycerols with a high proportion of unsaturated fatty acids have lower melting points than those rich in sam-rated fatty acids, so the former are oils - that is, they are liquid at room temperature. The unsaturated fatty acids are identified by the number of carbon atoms and the position of the double bonds (see below). 

TABLE 11-2 Fatty Acid Composition of E. coli Cells Cultured at Different Temperatures... 

The exact fatty acid composition depends not only on growth temperature but on growth stage and growth medium composition. 

Lipids in a biological membrane can exist in liquid-ordered or liquid-disordered states in the latter state, thermal motion of acyl chains makes the interior of the bilayer fluid. Fluidity is affected by temperature, fatty acid composition, and sterol content. 

Lipid Melting Temperatures Membrane lipids in tissue samples obtained from different parts of the leg of a reindeer have different fatty acid compositions. Membrane lipids from tissue near the hooves contain a larger proportion of unsaturated fatty acids than those from tissue in the upper leg. What is the significance of this observation ... 

Comparson of the transitions observed by differential scanning calorimetry in membranes of M. laidlawii and in water dispersions of the lipids from the membranes support the concept that most of the lipids exist as a smectic mesophase in the membranes. The evidence for a bilayer structure is straightforward in this case. Lipid transition temperatures are a function of fatty acid composition and correlate well with biological properties. The calorimeter possesses advantages over high resolution NMR for M. laidlawii, and perhaps in many other systems, because the data can be interpreted less ambiguously. In M. laidlawii membranes the bilayer appears to be compatible with the same physical properties observed in other membranes—a red-shifted ORD, lack of ft structure in the infrared, reversible dissociation by detergents, and poorly... 

Stearic acid is a long chain SFA present, to varying degrees, in virtually all edible fats and oils. Table IV provides the fatty acid composition of fats and oils commonly consumed by humans. The most abundant food sources of stearic acid in the American diet are beef fat and cocoa butter (chocolate). Cocoa butter is valued by chocolate manufacturers because it remains solid at room temperature but dissolves quickly at body temperature, a unique characteristic of chocolate that is due largely to stearic acid. During the last few decades as cocoa butter prices and supplies have fluctuated, food companies began looking for alternative oils that could provide equivalent amounts of stearic acid in order to retain the desirable physical characteristics. Several... 

Given, the same temperature conditions, the natural mobility rate is the determinant of specific oxygen uptake, energy metabolism, the ratio between protein and lipid used in metabolism, the level of tissue enzyme activity, the rate of self-replenishment of proteins, the energy capacity of tissues, the concentration of erythrocytes and haemoglobin in the blood, the lipid fraction and fatty acid composition of lipids in the liver and other tissues, and the pattern of mobilization in endogenous feeding. 

Cossins, A.R., Friedlander, M.J. and Prosser, C.L. (1977). Correlations between behavioural temperature adaptations of goldfish and the viscosity and fatty acid composition of their synaptic membranes. Journal of Comparative Physiology 120, 109-121. 

Farkas, T. (1984). Adaptation of fatty acid composition to temperature - a study on carp (Cyprinus carpio) liver slices. Comparative Biochemistry and Physiology 79B, 531-535. 

Farkas, T. and Herodek, S. (1964). The effect of environmental temperature on the fatty acid composition of crustacean plankton. Journal of Lipid Research 5,369-375. 

Kemp, P. and Smith, M.F. (1970). Effect of temperature acclimatization on the fatty acid composition of goldfish intestinal lipids. Biochemical Journal 117,9-15. 

Knipprath, W.G. and Mead, J.F. (1968). The effect of the environmental temperature on the fatty acid composition and on the in vivo incorporation of l-l4C-acetate in goldfish. Lipids 3,121-128. 

A commercial castor oil (Delaware-Brazil) was used as purchased without any pretreatment. The fatty acid composition was determined using a gas chromatograph (HP 5890) with a flame ionization detector. The following instrumentation and conditions were used H2 as carrier gas, modified polyethylene glycol column (FFAP 2 - 25 m x 0.20 mm id x 0.30-mm film), column temperature of 180-210°C (2°C/min), injector temperature of 250°C, and detector temperature of 280°C. Using this procedure, the approximate fatty acid composition in castor oil is 92 wt% ricinoleic acid and 8 wt% other acids. Ethyl alcohol (95 v/v%) (Merck) and n-hexane PA (Merck) were used as substrate and solvent, respectively. 

Cold properties of biodiesel are highly correlated to the fatty acid composition. Biodiesel with a high content of saturated fatty acids, such as that from palm oil and coconut oil, possesses poor cold flow properties. On the other hand, biodiesel with a high content of unsaturated fatty acids possesses better flow properties at lower temperatures. However, biodiesel from highly unsaturated fatty acids with more than two double bonds has combustion problems. Therefore, in some countries, the content of highly unsaturated fatty acid methyl esters in biodiesel is kept low (5). 

Fatty acid composition. High temperature processes can cause formation of trans-acids, particularly of trans-octadecenoic acids. The levels are quite small, but can be detected by GC on suitable columns (BPX70, CpSil88, etc.). Of particular relevance is the fact that these, once formed,... 

Usually the melting point of depot fat is only a few degrees below body temperature. The fatty acid composition of depot fat thus is a compromise between the requirement for keeping the fat liquid and the ability to store as much energy as possible. (Unsaturated fatty acids yield less energy than saturated ones of the same size, when oxidized.)... 

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