Definition: Iodine number is defined as the number of grams of iodine absorbed by 1 gram of fat. Example: Human fat: 65 – 69 Butter: 25–40 Coconut oil: 7 – 10 Significance Iodine number measures the degree of unsaturation of fatty acids in the fat. The iodine number for solid fats is lesser than that…
Definition: Acid Number is defined as the number of milligrams of KOH required to neutralise the free fatty acid present in 1 gram of fat. Example: Butter: 0.5 – 0.6 Coconut oil: 2.5 – 6 Significance: In normal circumstances, refined oils should be free from any free fatty acids. Oils, on decomposition due to chemical or…
Saponification number Definition: Saponification number is defined as the milligrams of KOH required to hydrolyse (saponify) one gram of fat or oil. Example: Human fat: 195 – 200 Butter: 230 – 240 Coconut oil: 250 – 260 Significance: The saponification number thus provides information on the average chain length of fatty acids in the fat.…
Fats and oils form essential constituent of diet. It is necessary to identify a pure fat or to determine the proportion of different types of fat mixed in edible oils and fats like butter and ghee. With an adequate knowledge of the characteristic properties of fats, it is possible to identify the fat under investigation…
Unsaturated fatty acids and esters can take up halogens like Br2 and I2 at their double bonds at room temperature in acetic acid or methanol solution. This reaction is the basis of the iodine number determination.
Unsaturated fatty acids either free or combined in lipids react with gaseous hydrogen to yield the saturated fatty acids.
Rancidification may be prevented by the following: Kries test is a delicate test used to detect oxidative rancidity. In this test, the fat is treated with ether, phloroglucinol, and hydrochloric acid. Positive test is indicated by the development of a red colour. This is due to the presence of epihydrin aldehyde, which is one of…
Oils that are rich in unsaturated fatty acids frequently undergo oxidation at ordinary temperature. The oxidation proceeds slowly and forms short chain fatty acids (C4 to C10) and aldehydes, which give a rancid taste and odour to the fats. This process is also known as oxidative rancidity because it undergoes autoxidation. Autoxidation takes place by free…
Involves partial hydrolysis of the glycerides to mono- and diglycerides while glycerol and free fatty acids are also liberated. The hydrolysis is hastened by the presence of moisture, warmth, and lipases present in fats. As a result of the liberation of volatile butyric acid, hydrolytic rancidity produces a disagreeable odour and taste in fats that…