Vegetable Oils and Fats 



363 



or without regard to their drying properties. In the class of semi-drying. oils, cotton seed and 

 the different rape oils are the most important. Among the . non-drying oils olive occupies 

 the first place, but ground or earth-nut oil is an important article of commerce. Palm oil is 

 perhaps the most useful of the vegetable fats, while the fatty products of the coco-nut palm 

 provide a valuable asset to the countries where the tree flourishes. 



The methods of obtaining the oil from the seeds or fruits depend partly upon their size, 

 hardness and. other qualities, also upon the consistency of the oil and the use for which it is 

 intended. There are two general methods adopted, (1) by expression, when the material is 

 crushed in a press and the oil squeezed out ; (2) by extraction, when the oil is dissolved out 

 by suitable solvents. The different modes of pressing out the oil vary greatly from the 

 primitive methods employed by natives of West Africa, India and elsewhere, to the modern 

 extensive equipments of Europe and America, as described for cotton seed- oil (see p. 368). 



The machines employed for cleaning and preparing vary with the raw material, e.g., cotton 

 seed and earth nut require to be decorticated, linseed and rape-seed have to be screened and 

 cleaned, coco-nuts are treated in a breaker or disintegrator. 



Previous to pressing, large seeds or bulky material are first reduced in an edge-runner seed 

 mill, consisting of two vertical stones revolving in a circular trough ; the final grinding, or, in 

 the case of small seeds, the only grinding, is performed in seed crushers. The crushers contain 

 one or more series of rollers, that are 

 grooved for breaking up palm kernels 

 and ground nut, or smooth for the 

 comminution of linseed or copra. 



The material is delivered from the 

 crushers as meal and passes at once, 

 or after a preliminary heating, to the 

 cake-moulding machine. The heat- 

 ing is carried out in large cylinders 

 known as "kettles," through which 

 steam pipes are led for warming the 

 meal ; besides rendering the oil more 

 fluid, the heating helps to break up 

 the oil-containing cells. 



The cold or heated seed-meal 

 is measured out automatically into 

 press cloths, that are generally made 

 of closely- woven cotton cloth encased 

 in close horse-hair cloth, and receives 

 a preliminary squeeze to mould the 

 material. The moulds or " cakes " 

 are next transferred to the press. 

 The presses are the most important 

 item in the installation, and vary 

 very considerably, but are all worked 

 by hydraulic power. In the open- 

 plate process the cakes enclosed 

 in the cloth covering are packed 

 between press-plates of a flat or 

 grooved pattern and piled in the 

 press. Twelve or more cakes are 

 pressed in one of these machines, 

 and the oil exudes from the meal 



Photo by W. H. Johnson, Esq., F.L.S. 



PALM OIL TREE 



