Polyunsaturated oils

Antioxidants are used to retard the reaction of organic materials with atmospheric oxygen. Such reaction can cause degradation of the mechanical, aesthetic, and electrical properties of polymers loss of flavor and development of rancidity ia foods and an iacrease ia the viscosity, acidity, and formation of iasolubles ia lubricants. The need for antioxidants depends upon the chemical composition of the substrate and the conditions of exposure. Relatively high concentrations of antioxidants are used to stabilize polymers such as natural mbber and polyunsaturated oils. Saturated polymers have greater oxidative stabiUty and require relatively low concentrations of stabilizers. Specialized antioxidants which have been commercialized meet the needs of the iadustry by extending the useflil Hves of the many substrates produced under anticipated conditions of exposure. The sales of antioxidants ia the United States were approximately 730 million ia 1990 (1,2). 

Fulmer R.W. 1990. Polyunsaturated oils. In World Oil Conference on Oleochemicals into the 21st Century. (T.H. Applewhite, ed.) pp. 94-104. American Oil Chemist s Society, Champaign, 111. 

Margarine made with polyunsaturated oils has essential fatty acids Cabbage... 

There have been three primary and eight secondary prevention trials in which dietary change was the only variable. Dietary modification included reduction in total fat, substitution of saturated fat by polyunsaturated oils and reduction in cholesterol intake. These changes resulted in a reduction of saturated fat intake by 27 55% and reductions in plasma cholesterol of up to 18%. However, with the exception of one study, the Lyon Diet Heart Study (de Lorgeril et al., 1994), neither total or CHD mortality was lowered significantly by the dietary interventions (Ravnskov, 1998 Parodi, 2004). In the successful Lyon Diet Heart Study, a Mediterranean-type diet was compared with the usual post-infarct prudent diet. Throughout this trial, plasma cholesterol levels were similar in both the treatment and control groups. 

Q Explain how unsaturations affect the properties of fats and oils. Compare the properties of saturated fats with those of polyunsaturated oils and partially hydrogenated vegetable oils. 

Health concerns about trans fatty acids formed by hydrogenation have lead to the use of interesterification, fractionation, or blending of saturated and polyunsaturated oils as an alternate method to hydrogenation. It was found... 

These unsaturated bonds can have the effect of mopping up oxidants made within the body, which can be harmful to cells. Most margarine is made from natural polyunsaturated oils and these are better for healthy living than the saturated fats in butter and cream. 

It is well-known that vitamins A and D are sensitive to oxygen, light, and the presence of oxidizing agents. Long-chain polyunsaturated oils are susceptible to... 

Being arbitrarily etassified as a saturated fat, palm oil has been postulated to increase serum cholesterol levels and hence enhance the risk of coronary heart disease (CHD). Recent findings, besides earher published literature, however, indicate that this hypothesis is not uniformly true. For instance, Kris-Etherton and co-workers (146) demonstrated that feeding a palm oil diet to rats did not raise plasma cholesterol in comparison to a highly polyunsaturated corn oil diet. Similarly, Sugano and co-workers (147) were unable to establish significant differences in plasma cholesterol in rats fed a palm olein diet compared to other polyunsaturated oils. Sundram and co-workers (148) compared the effect of palm oil and its... 

The 10% level of linoleic acid in palm oil seems ideal in meeting the nutritional requirements of this essential fatty acid, without eliciting growth responses in the tumor cells in comparison to more polyunsaturated oils. However, when compared... 

Scott and co-workers pioneered the development of rumen inert fats by demonstrating that the polyunsaturated fatty acids content of milk can be increased by feeding polyunsaturated oils encapsulated in formaldehyde-treated casein (71-74). Various types of domestically sold rumen inert fats are show in Table 17. Palm-quist and co-workers pioneered the feeding of calcium soaps to dairy cattle (75-77). Their work became the basis for Megalac, made from palm oil and stearin. 

Glycerine, a byproduct, is a major part of the economics. Other reactions also exist that are not listed here, for example, the heat bodying or blowing (oxidation) of polyunsaturated oils forms polymers that have unusual properties and are used in a variety of markets. Boiled or bodied hnseed oil is an example of this type of product. 

While the HCA concentration is low, at the ppb level, the carcinogenicity may be enhanced by polyunsaturated oils. Since high-fat western diets may promote aryl amine cancer, considerable importance is attached to the roles of HCAs and the related food-derived PhIP, or 2-amino-l-methyl-6-phenylimidazo[4,5-ft]pyridine (57), in the etiology of cancer. The mechanisms are similar to those encountered with other tumor-forming... 

Another paradox is that these polyunsaturated oils contain linoleic acid, which, in a series of steps, will convert cancer cells back to normal cells. A similar effect is observed for the theophylline contained in tea, whereas none was observed in... 

In temperate countries where palm olein crystallises or turns cloudy, blending with polyunsaturated oils is an easy and simple way to obtain a clear product for the retail supermarkets. The clarity of palm olein depends on its iodine value (Table 3.8) (Nor Aini andHanirah 1996,1997). The time that palm olein remains clear at 20°C varies from one day for oils of iodine value of 56 to more than 60 days for double fractionated oils of iodine value 65-67. 

Green, A.G. and Paul Dribnenki, J.C. (1994) Linola-A new premium polyunsaturated oil. Lipid Technol., 6, 29-33. 

Hydrogenation is used in the food industry to convert polyunsaturated vegetable oils into saturated solid fats. Partial hydrogenation is carried out to add hydrogen to some, but not all, double bonds in polyunsaturated oils. In this way liquid vegetable oils are converted into solid form. Crisco is one example of a hydrogenated vegetable oil. 

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