Fatty acids composition, edible fats/oils

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... 

FATTY ACID COMPOSITION (%) OF EDIBLE FATS AND OILS... 

TABLE 34.2 Fatty Acid Composition of Some Edible Oils and Fats ... 

Oxidative stability of edible oils depends primarily on their fatty acid composition and, to a lesser extent, in the stereospecific distribution of fatty acids in the triacyl-glycerol molecules. The presence of minor components in the oils also affects their oxidative stability. A detailed discussion of oxidative processes in fats and oils is provided elsewhere in this series. Oxidation may occur via different routes and includes autoxidation, photo-oxidation, thermal oxidation, and hydrolytic processes, all of which lead to production of undesirable flavor and products harmful to health. Flavor and odor defects may be detected by sensory analysis or by chemical and instrumental methods. However, chemical and instrumental procedures are often employed in the processing and during usage of edible oils. Indicators of oxidation are those that measure the primary or secondary products of oxidation as well as those from hydrolytic processes or from thermal oxidation, including polymers and polar components (15). 

Edible oils and fats are composed primarily of triacylglycerols (TAG), ester of one molecule of glycerol, and three molecules of fatty acids. Analysis of canola oils showed that TAGs constituted 94.4% to 99.1 % of the total lipid (2). The typical composition of canola, rapeseed, and soybean oils is presented in Table 1. 

Since fats and oils form essential nutrient of human diet, it is necessary to identify a pure fat or to determine the proportion of different types of fat or oil mixed as adulterant in edible oils and fats like butter and ghee. With an adequate knowledge of the characteristic composition of fats or oils, it is possible to identify the fat or oil under investigation. The chemical constants also give an idea about the nature of fatty acids present in fats or oils. Eventhough gas chromatographic method is available to identify and quantify the fatty acids present in fat or oil, the physical and chemical constants are still used in routine public health laboratories where such sophisticated facilities are lacking. 

Below is a table of the fatty acid compositions of selected common edible fats and oils. 

Animal fats are rendered tissne fats that can be obtained from a variety of animals. Examples of edible animal fats are butter, lard (pig fat), tallow, ghee, and fish oil. They are obtained from fats in the milk, meat, and under the skin of the animal. Typical fatty acid composition of some animal fats and oils are summarized in Table 5.5. 

Fats with Different Fatty Acid Composition. There is a vast body of knowledge on the different nutritional effects of different fatty adds. These will not be dealt with here. It is sufficient to stress here that it is important to avoid generalizations. Not all saturated fatty acids raise cholesterol. Not all polyunsaturated fatty acids reduce cholesterol and the physiologic effects of different trans fatty acids are different. In general, each fatty acid has distinct effects. Furthermore, it is important to keep in mind that the nutritional effects of edible fats and oils do not depend only on the fatty acids they contain but also on the presence of other components. 

Diacylglycerol (DAG) is an intermediate product of TAG hydrolysis and comprises up to 10% of glycerides in plant-derived edible fats and oils. Nagao et al. (7) showed that continuous DAG feeding suppressed the accumulation of fat in visceral and subcutaneous adipose tissues and reduced fat accumulation in the liver compared with TAG of the same fatty acid composition. 

Considerable effort has gone into changing the fatty acid composition of edible oils. This effort has been driven by concerns about oil stability, nutrition and the texture of plastic fats. 

Tezuka, T., Kuga, T. and Suzuki, S. (1%1) Fatty acid composition of edible fats and oils. (Gas-liquid chromatographic analysis). Anna. Rep. Natl. Inst. Nutr. Tokyo), 11-13. 

Fatty acid composition of edible fats and oils and of foodstuffs... 

The concentration of heavy metal ions that results in fat (oil) shelf-life instability is dependent on the nature of the metal ion and the fatty acid composition of the fat (oil). Edible oils of the linoleic acid type, such as sunflower and com germ oil, should contain less than 0.03 ppm Fe and 0.01 ppm Cu to maintain their stability. The concentration limit is 0.2 ppm for Cu and 2 ppm for Fe in fat with a high content of oleic and/or stearic acids, e. g. butter. Heavy metal ions trigger the autoxidation of unsaturated acyl lipids only when they contain hydroperoxides. That is, the presence of a hydroperoxide group is a prerequisite for metal ion activity, which leads to decomposition of the hydroperoxide group into a free radical ... 

Kostik, V., Memeti, S. and Bauer, B. (2013), Fatty acid composition of edible oils and fats. Journal of Hygienic Engineering and Design, 4, 112-116. 

Fats and oils always consist of a mixture of fatty acids, although one or two fatty acids are usually predominant. Table 1 shows the fatty acid composition of some edible fats rich in saturated fatty acids. In the Western diet, palmitic acid (Ci6 o) is the major saturated fatty acid. A smaller proportion comes from stearic acid (Ci8 o), followed by myristic acid (Ci4 o), lauric acid (Ci2 o) and short-chain and medium-chain fatty acids (MCFA) (Ci0 0 or less). 

Other parameters that are indirectly related to the composition of edible oils include iodine value and saponification value. The iodine value is a simple chemical constant for a fat or oil. It measures unsaturated or the average number of double bonds in fats and oils. Iodine value is defined as the number of grams of iodine that could be added to 100 g of oil, which is measured with the AOCS Method cd 1-25 (22). Meanwhile, saponification value is a measure of the alkali-reactive groups in fats and oils and is defined as the mg of KOH needed to saponify 1 g of oil. Shorter chain fatty acids give higher saponification values than do longer chain fatty acids. 

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