LIPIDES 81 



FATS 



Occurrence 



From the standpoint of natural abundance and commercial value, 

 fats are the most important of all the groups inchided in a lijMcle 

 classification. These simple lipides are found in virtually every living 

 tissue of plant or animal origin. They are stored in greatest quantity, 

 however, in the fat depots of the living organism. For example, in an 

 animal we find that fat reservoirs form beneath the skin, in the 

 abdomen and around the intestines, and surrounding such organs as 

 the heart, liver, and kidneys. Although small quantities of fat may 

 be deposited throughout a plant, the greatest concentration of reserve 

 lipide is located in the seed or fruit. 



Although heredity plays a very dominant role in the type and 

 amount of fat deposited in the various tissues of plants and animals, 

 environment also affects lipide deposition. For example, although 

 flax may be grown in climates ranging from fairly warm to cold, the 

 linseed fat (oil) obtained from the flaxseed of plants grown in one 

 climate will differ materially in both physical and chemical properties 

 from that of plants grown in another climate. In general, it can be 

 stated that the colder the climate, the greater will be the amount of 

 polyunsaturated acids found in the glyceride fraction. 



The activity of an animal largely governs the type of fat laid down 

 in the carcass. A very active animal deposits the harder saturated 

 fats in the tissues, whereas a sedentary member of the same species 

 tends to deposit the softer, more unsaturated fats. 



Diet also affects the nature of the carcass fat deposited by an animal. 

 For example, a hog fed on large quantities of peanut or cottonseed 

 meal deposits large quantities of unsaturated glycerides. These low- 

 melting glycerides, in turn, produce an undesirably oily carcass. Such 

 pork is referred to as soft pork. 



Physical Properties 



As explained in a previous section, fats may be either solids or 

 liquids at 20°C. Most of the common animal fats are solid at this tem- 

 perature, whereas the majority of vegetable fats (oils) are liquid at 

 the same temperature. In fact this solidity or liquidity at 20°C. has 

 served in the past as an arbitrary means of classification of these 

 simple lipides into animal fats (solids) and vegetable oils (liquids). 

 In many instances such a classification tends to be misleading, since 



