192 PLANT BIOCHEMISTRY 



salad oils. Flaxseed (linseed), tung, castor bean, and soybean oils have 

 found extensive application in the protective coating, linoleum, and 

 printer's ink fields. Palm and coconut oils are used extensively by the 

 detergent industry, particularly in the manufacture of synthetic deter- 

 gents. The fatty acid distribution in the oil is the governing factor 

 in determining the major use, although by means of hydrogenation 

 even the highly unsaturated oils are converted into satisfactory fats for 

 food and industrial purposes requiring greater stability. 



Tall oil. Tall oil is an ether-soluble complex isolated from coniferous 

 woods during pulping by the kraft sulfate process. It is a mixture of 

 fatty and rosin acids. After separation from the rosin acids by distilla- 

 tion, tall oil is sold to linoleum, protective coating, and detergent 

 industries in competition with other vegetable oils. 



Phospholipides. The phospholipides (phosphatides) represent a 

 group of combined or conjugated lipides containing a phosphoric 

 acid group in the molecule. Representative members are discussed 

 in Chapter 4. Phospholipides are components of vegetable oils such as 

 corn, rapeseed, soybean, linseed, and other plant oils. Plants contain 

 smaller amounts than are normally found in some animal tissues like 

 the liver and brain. It is probable phospholipides are components of 

 all living cells, with the greatest quantities found in tissues rich in fat. 

 Although this lipide fraction appears to parallel fats in quantitative 

 distribution, phospholipides do not occur in dispersed droplets (oil 

 vacuoles). There is good evidence that phospholipides are present in 

 tissues combined with proteins and possibly carbohydrates. In the 

 leaf this fraction appears to be confined to the grana of the chloro- 

 plasts. Phospholipides of the oil seeds disappear on germination, as 

 do the other lipides, but at a slower rate. The same statement is true 

 of the leaves, where, under starvation conditions, the triglycerides are 

 utilized at a more rapid rate than the phospholipides. There is some 

 question as to whether the latter compounds should be classified as 

 reserve lipides in the leaf or whether they should be considered to 

 have another function. Some recently published work indicates that 

 certain members of this group may play a role in phosphate transport 

 in the plant. Other members have been implicated in other group 

 transfer reactions in the organism. 



Although plants cannot be considered rich sources of the phos- 

 pholipides, quantities are recovered during refining of food and in- 

 dustrial oils. It is estimated that over 60,000,000 lb. of crude lecithin 

 is available annually as a by-product of the soybean oil refining 

 process. Crude "lecithin" is a mixture of compounds, including 

 lecithin, cephalin, phosphatidic acids, and sulfolipides. 



