Unsaturated fatty acid cis. Monounsaturated fatty acids have two carbon atoms attached by one double bond as a pair of hydrogen atoms is missing See: Basic Chemical Structure of an Unsaturated Fatty Acid.
Monounsaturated fats and oils are liquid at room temperature but start to solidify at refrigerator temperatures. Polyunsaturated fatty acids have more than one double bond in the carbon chain and therefore more than one pair of hydrogen atoms.
Polyunsaturated oils and fats are typically liquid at room temperature and in the refrigerator. Trans fatty acids are unsaturated fatty acids that have at least one double bond in the trans configuration. While most unsaturated fatty acids in foods have the cis configuration, trans fatty acids may also be present. Trans fatty acids in foods originate from three main sources:. Unsaturated fatty acid trans. The TFA content of bakery products rusks, crackers, pies, biscuits, wafers etc.
However, surveys have shown that levels of TFAs appear to be decreasing in these products as manufacturers reformulate to remove hydrogenated oils if present. Since the process of hydrogenation adds hydrogen atoms to oil, it will reduce the number of unsaturated fatty acids and increase the number of saturated fatty acids in the oil. Consumption of a high level of saturated fatty acids is associated with increasing the level of cholesterol in the blood and this may lead to coronary heart disease.
Therefore, as part of a healthy diet, consumers are advised to try to lower their intake of saturated fatty acids. Sometimes partial hydrogenation is carried out on oil as this will result in a lower level of saturated fatty acids formed in the product.
However, partial hydrogenation does lead to the formation of TFAs, rather than cis fatty acids. TFAs, like saturated fats are also associated with increasing cholesterol in the blood.
Although saturated fats also produce the 'good' cholesterol HDL , trans fats increase levels of the 'harmful' cholesterol LDL and decrease the good cholesterol. TFAs also lead to increased levels of triglycerides in the blood. In these respects trans fat could be considered as more likely to promote heart disease than and equivalent level of saturated fat.
However, to put this in context the intake of saturated fats in the European diet is approximately 10 times that of trans fats and therefore saturated fat in the diet is still considered to present the biggest risk with respect to heart disease. They concluded that the scientific evidence with regards to a possible relationship of TFA intake and cancer, type 2 diabetes or allergies was weak or inconsistent.
The major contributors to TFA in the diets of people in these 14 countries were edible fats and ruminant fat with bakery products and French fries being additional contributing foods in some countries. Forgot password? Don't have an account? Sign in via your Institution. You could not be signed in, please check and try again.
Sign in with your library card Please enter your library card number. Related Content Related Overviews fatty acid. Show Summary Details Overview hardening of oils. Reference entries hardening of oils in A Dictionary of Chemistry 6 Length: 34 words. All rights reserved. The degree of hydrogenation of unsaturated oils controls the final consistency of the product. What has happened to the healthfulness of the product which has been converted from unsaturated to saturated fats?
A major health concern during the hydrogenation process is the production of trans fats. Trans fats are the result of a side reaction with the catalyst of the hydrogenation process. This is the result of an unsaturated fat which is normally found as a cis isomer converts to a trans isomer of the unsaturated fat.
Isomers are molecules that have the same molecular formula but are bonded together differently. Focusing on the sp 2 double bonded carbons, a cis isomer has the hydrogens on the same side. Due to the added energy from the hydrogenation process, the activation energy is reached to convert the cis isomers of the unsaturated fat to a trans isomer of the unsaturated fat.
The effect is putting one of the hydrogens on the opposite side of one of the carbons. This results in a trans configuration of the double bonded carbons.
The human body does not recognize trans fats. Although trans fatty acids are chemically "monounsaturated" or "polyunsaturated," they are considered so different from the cis monounsaturated or polyunsaturated fatty acids that they can not be legally designated as unsaturated for purposes of labeling.
0コメント