A CACAO PRESS.
Reproduced by permission
of Messrs. Lake, Orr
& Co., Ltd.
The liquified cacao bean or "mass," simply mixed with sugar and cooled until it becomes a hard cake, has been used by the British Navy for a hundred years or more for the preparation of Jack's cup of cocoa. It produces a fine rich drink much appreciated by our hardy seamen, but it is somewhat too fatty to mix evenly with water, and too rich to be suitable for those with delicate digestions. Hence for the ordinary cocoa of commerce it is usual to remove a portion of this fat.
If "mass" be put into a cloth and pressed, a golden oil (melted cacao butter) oozes through the cloth. In practice this extraction of the butter is done in various types of presses. In one of the most frequently used types, the mass is poured into circular steel pots, the top and bottom of which are loose perforated plates lined with felt pads. A number of such pots are placed one above another, and then rammed together by a powerful hydraulic ram. They look like the parts of a slowly collapsing telescope. The "mass" is only gently pressed at first, but as the butter flows away and the material in the pot becomes stiffer, it is subjected to a gradually increasing pressure. The ram, being under pressure supplied by pumps, pushes up with enormous force. The steel pots have to be sufficiently strong to bear a great strain, as the ram often exerts a pressure of 6,000 pounds per square inch. When the required amount of butter has been pressed out, the pot is found to contain not a paste, but a hard dry cake of compressed cocoa. The liquified cacao bean put into the pots contains 54 to 55 per cent. of butter, whilst the cocoa press-cake taken out usually contains only 25 to 30 per cent. The expressed butter flows away and is filtered and solidified (see [page 158]). All that it is necessary to do to obtain cocoa from the press cake is to powder it.
SECTION THROUGH CACAO PRESS-POT AND RAM-PLATE.
(j) Breaking Down the Press Cake to Cocoa Powder.
The slabs of press-cake are so hard and tough that if one were banged on a man's head it would probably stun him. They are broken down in a crushing mill, the inside of which is as full of terrible teeth as a giant's mouth, until the fragments are small enough to grind on steel rollers.
(k) Sieving.
As fineness is a very important quality of cocoa, the powder so obtained is very carefully sieved. This is effected by shaking the powder into an inclined rotating drum which is covered with silk gauze. In the cocoa which passes through this fine silk sieve, the average length of the individual particles is about 0.001 inch, whilst in first-class productions the size of the larger particles in the cocoa does not average more than 0.002 inch. Indeed, the cocoa powder is so fine that in spite of all precautions a certain amount always floats about in the air of sieving rooms, and covers everything with a brown film.