Hydraulic press extraction

Mechanical Pressing. Historically, the first large commercial production of oils from seeds and nuts was carried out using labor-intensive hydraulic presses. These were gradually replaced by more efficient mechanical and screw presses. Solvent extraction was developed for extraction of seeds having low oil content. For seeds and nuts having higher oil content, a combination of a screw press followed by solvent extraction is a common commercial practice (prepress—solvent extraction). 

Presses are of two basic types hydraulic batch presses and screw presses. Hydraulic presses are used for extracting fruit juices, and screw presses for dewatering materials such as paper pulp, rubbish and manure. The equipment used is described in the handbooks Perry et al. (1997). 

When the stuff is sufficiently bleached, tho clear liquid is pumped into a cistern for further use—it being a property of the liquid that it not only extracts but destroys the color, and, therefore, does not becomo impure by bleaching. On the other hand, the stuff or pulp is put into a strong iron box, and submitted to the action of a hydraulic press, which prepares it for the beating engine. 

The saccharine liquid is extracted from the cane by pressure. The etigar-mills employed for this purpose are chiefly three, namely, the horizontal and the vertical roller mill, and the hydraulic press. The latter,... 

Hydraulic Pressing. Batch pressing was the earliest commercial method of oil extraction. Hydraulic equipment replaced the mechanical operations and the method became known as hydraulic pressing (49). In open presses, oilseed meals were wrapped in cloths and placed between plates, which were then gradually... 

The modem commercial methods of oil extraction from oilseeds include (1) batch hydraulic pressing Oil seeds are expressed by hydraulic pressure to yield oil (2) continuous mechanical pressing Oil seeds are squeezed through a tapering outlet and oil is expressed by the increasing pressure and (3) solvent extraction Oil seeds are extracted with solvent followed by removal of solvent to yield oil. These methods are also employed in the extraction of sesame seeds with some modification. 

The extraction of sesame oil from roasted sesame seed is generally performed with pressing. Solvent extraction is not used because the desirable roasted flavor may be removed during evaporation of solvent. In commercial production, continuous screw-press or hydraulic press is employed (42). The hydraulic press can be vertical or horizontal. The continuous screw may be operated twice in order to increase the oil yield (82). Proper cooking (100°C, 7 min) and addition of water (12.5%) after roasting can also raise the oil yield (83). 

Sesame oil from roasted sesame seed has the characteristic flavor and color of the roasted sesame oil the filtered crude oil is used without further refining. Sesame oil from cold-pressed unroasted sesame seed is also used directly after filtration as a flavored oil. Crude sesame oil from unroasted sesame seeds after screw-press or hydraulic press or solvent extraction, which varies in color from yellow to dark amber, may need further refining. Refined sesame oil is usually pale yellow in color. 

In 1795, J. Bramah of England invented the hydraulic press for oil extraction (1). Oilseeds were milled, cooked, and wrapped in filters cloths woven from horse-hair. The oilseeds wrapped in hlter cloths were manually loaded into perforated, horizontal boxes below the head block and above the ram of the press. The boxes were pressed together using upward hydraulic pressure on the ram. The oil was pressed out through the filter cloths surrounding the oilseeds. The filter cloths and spent cake were manually removed from the hydraulic press. The residual oil in spent cake was approximately 10%. 

Hydraulic press oil mills remained in use as late as the 1950s before the last of them were replaced with continuous screw presses and continuous solvent extraction plants, both of which required far less labor and could process at much higher rates. 

Today, continuous screw-presses dominate the mechanical extraction of fats. The only applications still favoring hydraulic presses are those requiring gentle handling, for example, pressing cocoa butter from cocoa beans where the defatted residue is to be fine-ground to make cocoa powder. The development of continuous screw-presses will be outlined in Section 4.2. The development and technology of hydraulic presses was covered in detail in previous editions of this book (109). This edition briefly summarizes the early development of hydraulic presses and then focuses on modern, continuous cocoa butter hydraulic presses used today. 

Sesame oil is obtained from the ripe seeds of one or more cultivated varieties of Sesamum indicum Linne (Earn. Pedalia-ceae) by expression in a hydraulic press or by solvent extraction. The crude oil thus obtained is refined to obtain an oil suitable for food or pharmaceutical use. Improved color and odor may be obtained by further refining. 

Derivation Hydraulic press or expeller extraction from coconut meat followed by alkali-refining, bleaching, and deodorizing. 

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