GB2125269A

GB2125269A - The size reduction of oil seeds

Info

Publication number: GB2125269A
Application number: GB08213370A
Authority: GB
Inventors: Ismail Hassan Hussein; Godfrey Vaughan Jeffreys
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-05-08
Filing date: 1982-05-08
Publication date: 1984-03-07

Abstract

Castor beans were treated with a freezing agent such as solid carbon dioxide, a mixture thereof with an organic solvent, or liquid nitrogen, prior to milling them in a grinder. The beans were solidified as a result of the freezing treatment so that there was no apparent oil loss when they were ground. The process was applied successfully both to whole and dehulled beans, as well as to other oilseeds, e.g. soyabeans, peanuts and sunflower seeds. It was possible to dehull soyabeans and to remove the skin of shelled and unshelled peanuts using this method, when freezing was conducted in a freeze dryer

Description

SPECIFICATION The size-reduction of castor seeds The castor oil seeds (Ricinus Communis, L.) are the source of castor oil and castor pomace. Castor oil is an important industrial oil that finds application in the manufacture of paints, resins, synthetic flavours and perfumes, plasticizers, artificial leathers and rubbers, nylons, insecticides, detergents, waxes, and many other products. The cake (or pomace) left after oil extraction is rich in protein but cannot be commercially utilized due to the presence of toxins and allergens in it. In the course of developing a process for the direct solvent extraction of castor seeds and the detoxification of the pomace, the problem of reducing the size of the seeds had to be solved.

Before vegetable oils can be extracted mechanically or by solvents, the oil-bearing seeds or nuts must undergo certain treatment to facilitate oil removal. Thus, after cleaning the seeds (and hulling them if this is applicable) they are reduced to small particles or thin flakes to make subsequent thermal or solvent treatment more effective.

The methods employed for production of vegetable oils are either straight mechanical pressing, or direct solvent extraction, or prepressing followed by solvent extraction. For most of the high oil content seeds the third method mentioned above is preferred due to the technical difficulties encountered in their direct solvent extraction. Because castor seeds have a high oil-content (50%) and because of their softness it is not advisable to flake them on equipment designed for other oilseeds, which usually consists of adjacent pairs of steel rolls or five-high rolls. It appears that the present practice is to press the castor beans without reducing their size, mostly because of the loss of oil that can take place. The resulting cake may be flaked prior to solvent extraction which removes the rest of the oil.

The present invention relates to a method of treatment of the castor beans which causes the said beans to be in such a state that their size can be reduced without any appreciable loss of oil.

The procedure discovered consists of contacting the beans with a freezing substance, be it a solid or a liquid or a mixture of both, in a suitable apparatus for a sufficient time to allow them to solidify. The beans may be decorticated or they may be fed as whole beans, although it is desirable to decorticate them prior to freezing because of the advantages of hull removal.

The freezing substance can be solid carbon dioxide (Cardice), or liquid nitrogen, or a mixture of Cardice and an organic solvent (ethanol, acetone, ... etc), or any other suitable substance. In most of our experiments we employed Cardice because it lowered the temperature sufficiently for our purpose in a short time, was cheap and easy to handle and store. Liquid nitrogen was more expensive and more difficult to handle. The mixtures of Cardice and organic solvents were satisfactory but the castor seed particles turned grey on storage when some of these mixtures were used for freezing the beans.

The contact between the beans and the freezing substance can be achieved in any suitable container. Special apparatus and precautions are needed for liquid nitrogen. The Cardice was crushed and mixed in a closed cylinder with the beans, care being exercised to allow the carbon dioxide gas to vent periodically. If it is desired not to vent the gas for any reason, the vessel in which the beans are mixed with the Cardice must be designed to bear the pressures experienced. The vessel was manually rolled to obtain intimate contact between the Cardice and the beans.

The time of contact may vary according to the freezing substance used and whether the beans are huiled or not. The hulled beans were found to solidify in a shorter time than the unhulled beans, as would be expected. With Cardice, it is safe to allow ten minutes of intimate contact between the unhulled beans and the Cardice.

The beans were then placed in a domestic coffee grinder with a sufficient amount of Cardice, and their size was reduced to the required level without an appreciable loss of oil. Because of the cell rupture that follows from the freezing and the grinding processes, it is advisable to make this treatment immediately before the actual extraction stage; this avoids the oil losses that could happen if the particles are allowed to return to normal temperatures.

The foregoing procedure could be applied, with any necessary modifications, to other high oilcontent seeds e.g. peanuts and sunflower seeds, as well as the low content oilseeds, e.g. soybeans.

During the tests involving peanuts and soybeans, it was found possible to remove the skin of shelled peanuts and the hull of the soybeans as follows. The peanuts and the soybeans were treated as above and the solidified nuts and beans were rubbed gently but firmly between two rough surfaces, whereupon the skin of the former and the hull of the latter were removed. The process was facilitated by prolonging the time of contact between the nuts and beans and the freezing medium. Hence the freezing was carried out in a freeze-dryer for periods varying between 8 hours and 25 hours. At the end of 8 hours operation, the soybeans were completely decorticated and the skin was removed from both the shelled and unshelled peanuts.

The advantages of the size reduction technique described in this invention can be summarized as follows: 1. The oil losses become negligible.

2. The method can be extended to other oil seeds, especially those with a high oil-content.

3. The need for flakers is eliminated; the savings may prove to be substantial because of the high power consumption associated with this operation.

4. The technique has the potential of application for the dehulling of small oil seeds.

5. The cell rupture that accompanies freezing may facilitate oil removal.

6. The technique offers the possibility of reducing the number of process units by allowing more than one operation to be carried out in the same piece of equipment.

Claims

1. A method for the size reduction of castor oilseeds in which the said beans are contacted with a freezing agent and ground in a suitable container. The freezing and grinding processes may be carried out separately, or the grinding may be done in the presence of the freezing agent for which any suitable substance can be used, e.g.

solid carbon dioxide, liquid nitrogen, ... etc.

2. A method as in claim 1 for the size reduction of other oilseeds, of high or low oil content, e.g.

sunflower, cottonseeds,... etc., hulled or unhulled.

3. A method as in claim 1 that can be operated on a continuous basis in a suitable device.

4. A method as in claim 1 for the dehulling of small oilseeds that involves freezing the chosen beans, e.g. soybeans, for longer times than is required for size reduction alone. One suitable device for this purpose is a freeze-dryer, and the beans are retained for such a time that will ensure removing the hull due to the action of the freezing process.