The Manufacture of Chocolate and other Cacao Preparations

by Paul Zipperer

The cleaned beans are first very superficially roasted, to facilitate winnowing, and the cacao thus treated (half roasted cacao) broken as small as possible, which is an equally important factor in the shelling and winnowing processes. It should be observed here that the less the cacao has been roasted, the finer it should be broken. The material is then impregnated by one of the above-mentioned alkaline solutions, which is sprayed on to the beans. The chief agent employed is potash (carbonate of potassium) in the proportion of 1½-2 (3 at the outside) parts of potash to 20-30 parts of water, for every hundred parts of the defatted material to be treated. Some manufacturers use sodium or a mixture of sodium and carbonate of magnesia in place of the potash. As soon as the cacao has been uniformly impregnated by the alkaline solution, the roasting process should be completed. Still more care should be devoted to the roasting of cacao for pulverising than is required in the case of eating chocolates, as taste and smell play a more important part and the point of complete roasting is not so easily recognised. The cacao being roughly broken and the shells removed, the second roasting process must of course be conducted over a low fire. The most suitable machines for this purpose are the large roasting machines illustrated on page 93, Fig. 14, as in these machines there is little possibility of over-roasting, even when dealing with large quantities and the machine is intensely heated; another advantage is the easy accessibility of the roasting drum, which can be immediately exposed by removing the front cover, for cleaning; cleaning is very necessary in roasting machines. Broken and moistened cacao chars much more readily than raw beans which have not been deprived of their shells. If it is not possible to thoroughly clean the interior of the roasting drum, as is often the case with spherical roasters, the particles of cacao remaining in the drum continually undergo re-roasting, finally falling in a completely charred state into the cacao, thereby greatly prejudicing its taste.

If necessary, the cacao can now be passed through the breaking machine again, from which it is transferred to the triple cacao mill, which provides for fine grinding. The material is then deposited in heated pans (see page [117], Fig. 27) where it remains until ready for the next process, the expression of the fat. The object of the fine grinding in the mill is to render the cacao on being ground again after the defatting process, easily capable of being sifted, and to obtain a preparation which, on being mixed with hot water, leaves as little sediment as possible.

2. Expression of the Fat.

Hydraulic presses are nowadays exclusively used for this most important operation in the manufacture of “soluble” cocoa. The methods of pressing have, in common with the other operations in the course of manufacture, undergone considerable modification and improvement.

According to Macquer (see Mitscherlich, S. 58) the butter was extracted during the last century by pulverising the seeds, boiling them in water and cleansing the fat, which, on cooling, congealed on the surface of the water, by re-melting. According to Desprez (see Mitscherlich, S. 58), burned, shelled and finely pulverised beans were spread to a height of 12-15 inches on coarse linen or canvas, which was spanned across a vessel containing boiling water, to expose the fine powder thoroughly to the action of the hot vapour. The powder was then pressed, in linen bags, between two tin plates, whereby some 50% of pure cacao butter was obtained. At a later period the heatable hydraulic pot-presses came into use. The mass had, however, to be introduced into these pots tied up in a cloth or sack, to facilitate which it was previously treated with water, forming a thickish syrup very convenient for pressing. All these methods, however, were attended with the great disadvantage that the cocoa, after being stored some time, acquired a grey colour, or became mouldy. To avoid these undesirable results presses were constructed which rendered it possible to liquefy the mass without any further treatment in the receptacle in which the pressing was conducted. Such a press, likewise acting hydraulically, is shown in Fig. 82 on the opposite page.

This machine exerts a total pressure of 320000 kilogrammes and works with 400 atmospheres. The construction of the machine is similar to that of the well-known types of presses used by oil manufacturers for the preparation of vegetable oils. When pressing, however, the pots containing the cacao must be rendered water-tight both at the top and bottom, to prevent the liquid cacao from escaping, while such provision is not necessary in the case of the oil presses. The stopping up of the press-pots is effected by means of a side-handle, and arrangements are provided for heating the pots both from above and below. The machine illustrated has 4 pots, arranged one above the other, which can be drawn out on guide-rails towards the front of the machine. During pressing, they close telescopically with the piston arranged underneath each pot. The pump which supplies the water for the hydraulic pressure, works perfectly automatically, increases the pressure according to the quantity of fat which has run off and keeps the pressure at its maximum or at any degree required. With these presses it is possible to extract, without difficulty, 85 % and even more of the total fat of the cacao bean. If pressing is carried on at too high a temperature, a pale, whitish grey butter is the result. If, however, a little attention is paid by the operator at the press, the butter obtained is usually perfectly clear, as it is first conducted through a horse-hair pad covered with linen, or a camel-hair cushion 15 millimetres in thickness. Sufficient attention is not always paid to the operation of pressing, so that it often happens that some of the cacao escapes with the butter, which is especially the case if the pressure has been increased too rapidly at the beginning. If the butter is extracted for use in the factory itself, the escape of the cacao with it is of no serious consequence; if, however, the butter is intended for sale for commercial purposes, its appearance is a most important factor, wherefore it is advisable to filter the impure fat immediately after pressing. It is true that, in most factories, the butter is in such cases merely remelted to allow the impurities to settle to the bottom, this part being then submitted again to the same treatment, while the rest of the butter is disposed of on the market. If filtering is necessary, the butter filter should be used, which, first constructed in Holland, has been in use for a long time there. The principle of these filters is to pass the butter through hanging tubes made of a filtering material similar to flannel.

Fig. 82.

The firm of Volkmar Hänig & Co. constructs special cocoa butter filters which can be obtained through the firm of J. M. Lehmann. Figs. 83 and 83a show this type of filter (cross and vertical section), the manner of working with it being the following:

As soon as the butter has passed through the hair sieve in the upper part of the apparatus, which removes larger objects such as pieces of wood etc., it enters the hanging filter tubes, which, to facilitate cleaning, are interchangeable. The filter butter accumulates in the large space provided for the purpose and is withdrawn through a tap. An observing glass is attached to the apparatus for the purpose of watching the height of the butter, and the whole filter is water-jacketed, the water being heated by a steam coil fixed in the bottom of the apparatus. A thermometer is fixed to the side of the filter, for regulating the temperature.