PLANT STRUCTURE AND COMPOSITION 



191 



"ether extractables," and includes the triglycerides, phospholipides, 

 and waxes as well as the non-fatty-acid-containing substances, resins, 

 resin acids, terpenes (essential oils), and plant sterols. 



Fats and oils. Fats and oils are found in the greatest quantity in 

 storage regions of the plants, particularly in the seeds or fleshy cover- 

 ings of certain seeds, but they occur in all parts of the plant in small 

 quantities. In general, the vegetative organs contain only small quan- 

 tities of fats. The fat content of leaf tissue varies from 0.5 to 5 per 

 cent in common species. Stems and bark tissue contain similar 

 amoimts. Seeds and fruits vary widely in their oil content. Wheat, 

 oats, corn, and barley contain from 2 to 5 per cent oil, whereas the oil 

 seeds may contain up to 60 per cent oil. Most fruits are low in oil; 

 however, the avocado contains about 20 per cent and the olive fruit 

 50 per cent. Both the total triglyceride content and the fatty acid 

 distribution within the fat or oil vary in different fruits. Table 8-3 

 shows the oil content and major fatty acid composition of some of the 

 common oil seeds and fruits. It must be remembered that these are 

 average values. Within limits biological variation and varietal dif- 

 ferences influence both the oil content and the composition. 



In addition to the commodities mentioned in Table 8-3, rapeseed 



TABLE 8—3. Oil Content and Composition of Some Seeds and Fruits 



and sesame seed oils constitute important sources of industrial and 

 food oils in some parts of the world. Total world production of vege- 

 table oils for food and industrial purposes is in excess of 25,000,000 

 tons. Peanut, cottonseed, soybean, coconut, olive, and corn oils are 

 used extensively in the food industry for shortenings, margarines, and 



