Measures of Unsaturation

It is obvious, then, that it is important for industrial users of fats to know the degree of unsaturation of a given parcel of fat. This might be ascertained by determining the amount of hydrogen required to convert it into a saturated fat. In practice this is a complicated procedure and so simpler methods are resorted to. The simplest of these is the determination of the amount of iodine that can be made to combine with the fat. The percentage by weight of iodine absorbed by the fat in the natural state is known as the iodine number. It is an index to the degree of unsaturation of the fat. The fats with the highest iodine numbers are the drying oils par excellence, linseed and tung oil, with which must also be classified menhaden fish oil.

Revision exercises

Ex.1. Answer the following questions:

1. What is the role of food in human nutrition? 2. What are the physical and chemical properties of fats? 3. What does the classification of fats depend on? 4. What is the difference between fats and oils? 5. What is the process of rancidification? 6. What is the difference between saturated and unsaturated fatty acids? 7. What is the iodine number?

Ex.2. Match the words with their definitions:

1. rancid	a. oily in appearance, texture, or manner;
2. greasy	b. any of a class of often fragrant organic compounds represented by the formula RCOOR and that are usually formed by the reaction between an acid and an alcohol with elimination of water;
3. unpalatable	c. any of various substances that are soluble in nonpolar organic solvents (as chloroform and ether), that are usually insoluble in water, that with proteins and carbohydrates constitute the principal structural components of living cells, and that include fats, waxes, phosphatides, cerebrosides, and related and derived compounds;
4. ester	d. the act or process of nourishing or being nourished; specifically the sum of the processes by which an animal or plant takes in and utilizes food substances;
5. lipid	e. having a rank smell or taste usually from chemical change or decomposition;
6. nutrition	f.distasteful, disagreeable, unpleasant.

Ex.3. Say whether the following statements are true or false:

1. The percentage by weight of iodine absorbed by the fat in the natural state is known as the iodine number. 2. The fatty acids without carbon-carbon double bonds are classified as unsaturated, and those containing carbon-carbon double bonds are classified as saturated. 3. Unsaturated fatty acids can be made to combine with other substances instead of with oxygen. 4. Lipids are cellular compounds that are soluble in water. 5. The oleic, linolic, and linolenic acids are liquids at ordinary temperatures. 6. Fats and oils are practically always mixtures of triglycerids in varying proportions.

Ex.4. Insert the necessary word: