Cocoa and Chocolate Part 11

This is a box fitted with shaking sieves down which the cacao beans pa.s.s in a current of air. Having come over some large and very powerful magnets, which take out any nails or fragments of iron, they fall on to a sieve (1/4-inch holes) which the engineer describes as "rapidly reciprocating and arranged on a slight incline and mounted on spring bars." This allows grit to pa.s.s through. The beans then roll down a plane on to a sieve (3/8-inch holes) which separates the broken beans, and finally on to a sieve with oblong holes which allows the beans to fall through whilst retaining the cl.u.s.ters. The beans encounter a strong blast of air which brushes from them any sh.e.l.l or dust clinging to them.]

(_c_) _Roasting the Beans._

As with coffee so with cacao, the characteristic flavour and aroma are only developed on roasting. Messrs. Bainbridge and Davies (chemists to Messrs. Rowntree) have shown that the aroma of cacao is chiefly due to an amazingly minute quant.i.ty (0.0006 per cent.) of linalool, a colourless liquid with a powerful fragrant odour, a modification of which occurs in bergamot, coriander and lavender. Everyone notices the aromatic odour which permeates the atmosphere round a chocolate factory. This odour is a bye-product of the roasting shop; possibly some day an enterprising chemist will prevent its escape or capture it, and sell it in bottles for flavouring confectionery, but for the present it serves only to announce in an appetising way the presence of a cocoa or chocolate works.

[Ill.u.s.tration: SECTION THROUGH GAS HEATED CACAO ROASTER.]

Roasting is a delicate operation requiring experience and discretion.

Even in these days of scientific management it remains as much an art as a science. It is conducted in revolving drums to ensure constant agitation, the drums being heated either over c.o.ke fires or by gas. Less frequently the heating is effected by a hot blast of air or by having inside the drum a number of pipes containing super-heated steam.

[Ill.u.s.tration: ROASTING CACAO BEANS.

(Messrs. Cadbury Bros'. Works, Bournville).]

The diagram and photo show one of the types of roasting machines used at Bournville. It resembles an ordinary coffee roaster, the beans being fed in through a hopper and heated by gas in the slowly revolving cylinder. The beans can be heard lightly tumbling one over the other, and the aroma round the roaster increases in fullness as they get hotter and hotter. The temperature which the beans reach in ordinary roasting is not very high, varying round 135 C. (275 F), and the average period of roasting is about one hour. The amount of loss of weight on roasting is considerable (some seven or eight per cent.), and varies with the amount of moisture present in the raw beans.

There have been attempts to replace the aesthetic judgment of man, as to the point at which to stop roasting, by scientific machinery. One rather interesting machine was so devised that the cacao roasting drum was fitted with a sort of steelyard, and this, when the loss of weight due to roasting had reached a certain amount, swung over and rang a bell, indicating dramatically that the roasting was finished. As beans vary amongst other things in the percentage of moisture which they contain, the machine has not replaced the experienced operator. He takes samples from the drum from time to time, and when the aroma has the character desired, the beans are rapidly discharged into a trolley with a perforated bottom, which is brought over a cold current of air. The object of this refinement is to stop the roasting instantly and prevent even a suspicion of burning.

After roasting, the sh.e.l.l is brittle and quite free from the cotyledons or kernel. The kernel has become glossy and friable and chocolate brown in colour, and it crushes readily between the fingers into small angular fragments (the "nibs" of commerce), giving off during the breaking down a rich warm odour of chocolate.

(_d_) _Removing the Sh.e.l.ls._

It has been stated (see _Fatty Foods_, by Revis and Bolton) that it was formerly the practice not to remove the sh.e.l.l. This is incorrect, the more usual practice from the earliest times has been to remove the sh.e.l.ls, though not so completely as they are removed by the efficient machinery of to-day.

[Ill.u.s.tration: CACAO BEAN, Sh.e.l.l AND GERM.]

In _A Curious Treatise on the Nature and Quality of Chocolate_, by Antonio Colmenero de Ledesma (1685), we read: "And if you peel the cacao, and take it out of its little sh.e.l.l, the drink thereof will be more dainty and delicious." Willoughby, in his _Travels in Spain_, (1664), writes: "They first toast the berries to get off the husk," and R. Brookes, in the _Natural History of Chocolate_ (1730), says: "The Indians ... roast the kernels in earthen pots, then free them from their skins, and afterwards crush and grind them between two stones."

He further definitely recommends that the beans "be roasted enough to have their skins come off easily, which should be done one by one, laying them apart ... for these skins being left among the chocolate, will not dissolve in any liquor, nor even in the stomach, and fall to the bottom of the chocolate-cups as if the kernels had not been cleaned."

That the "Indian" practice of removing the sh.e.l.ls was followed from the commencement of the industry in England, is shown by the old plate which we have reproduced on p. 120 from _Arts and Sciences_.

The removal of the sh.e.l.l, which in the raw condition is tough and adheres to the kernel, is greatly facilitated by roasting. If we place a roasted bean in the palm of the hand and press it with the thumb, the whole cracks up into crisp pieces. It is now quite easy to blow away the thin pieces of sh.e.l.l because they offer a greater surface to the air and are lighter than the compact little lumps or "nibs" which are left behind. This ill.u.s.trates the principle of all sh.e.l.ling or husking machines.

(_e_) _Breaking the Bean into Fragments._

The problem is to break down the bean to just the right size. The pieces must be sufficiently small to allow the nib and sh.e.l.l readily to part company, but it is important to remember that the smaller the pieces of sh.e.l.l and nib, the less efficient will the winnowing be, and it is usual to break the beans whilst they are still warm to avoid producing particles of extreme fineness. The breaking down may be accomplished by pa.s.sing the beans through a pair of rollers at such a distance apart that the bean is cracked without being crushed. Or it may be effected in other ways, _e.g._, by the use of an adjustable serrated cone revolving in a serrated conical case. In the diagram they are called kibbling cones.

[Ill.u.s.tration: SECTION THROUGH KIBBLING CONES AND GERM SCREENS.]

(_f_) _Separating the Germs._

About one per cent. of the cacao bean fragments consists of "germs." The "germ" is the radicle of the cacao seed, or that part of the cacao seed which on germination forms the root. The germs are small and rod-shaped, and being very hard are generally a.s.sumed to be less digestible than the nib. They are separated by being pa.s.sed through revolving gauze drums, the holes in which are the same size and shape as the germs, so that the germs pa.s.s through whilst the nib is retained. If a freakish carpenter were to try separating shop-floor sweepings, consisting of a jumble of chunks of wood (nib), shavings (sh.e.l.l) and nails (germ) by sieving through a grid-iron, he would find that not only the nails pa.s.sed through but also some sawdust and fine shavings. So in the above machine the finer nib and sh.e.l.l pa.s.s through with the germ. This germ mixture, known as "smalls" is dealt with in a special machine, whilst the larger nib and sh.e.l.l are conveyed to the chief winnowing machine. In this machine the mixture is first sorted according to size and then the nib and sh.e.l.l separated from one another. The mixture is pa.s.sed down long revolving cylindrical sieves and encounters a larger and larger mesh as it proceeds, and thus becomes sieved into various sizes. The separation of the sh.e.l.l from the nib is now effected by a powerful current of air, the large nib falling against the current, whilst the sh.e.l.l is carried with it and drops into another compartment. It is amusing to stand and watch the continuous stream of nibs rushing down, like hail in a storm, into the screw conveyor.

[Ill.u.s.tration: SECTION THROUGH WINNOWING MACHINE.]

This is the process in essence--to follow the various partially separated mixtures of sh.e.l.l and nib through the several further separating machines would be tedious; it is sufficient for the reader to know that after the most elaborate precautions have been taken the nib still contains about one per cent. of sh.e.l.l, and that the nib obtained is only 78.5 per cent. of the weight of raw beans originally taken. Most of the larger makers of cocoa produce nib containing less than two per cent. of sh.e.l.l, a standard which can only be maintained by continuous vigilance.

[Ill.u.s.tration: CACAO GRINDING.

A battery of horizontal grinding mills, by which the cacao nibs are ground to paste (Messrs. Cadbury Bros., Bournville.)]

The sh.e.l.l, the only waste material of any importance produced in a chocolate factory, goes straight into sacks ready for sale. The pure cacao nibs (once an important article of commerce) proceed to the blenders and thence to the grinding mill.

(_g_) _Blending._

We have seen that the beans are roasted separately according to their kind and country so as to develop in each its characteristic flavour.

The pure nib is now blended in proportions which are carefully chosen to attain the result desired.

(_h_) _Grinding the Cacao Nibs to Produce Ma.s.s._

In this process, by the mere act of grinding, the miracle is performed of converting the brittle fragments of the cacao bean into a chocolate-coloured fluid. Half of the cacao bean is fat, and the grinding breaks up the cells and liberates the fat, which at blood heat melts to an oil. Any of the various machines used in the industries for grinding might be used, but a special type of mill has been devised for the purpose.

In the grinding room of a cocoa factory one becomes almost hypnotised by a hundred of these circular mill-stones that rotate incessantly day and night. In Messrs. Fry's factory the "giddy motion of the whirling mill"

is very much increased by a number of magnificent horizontal driving wheels, each some 20 feet in diameter, which form, as it were, a revolving ceiling to the room. Your fascinated gaze beholds "two or three vast circles, that have their revolving satellites like moons, each on its own axis, and each governed by master wheels. Watch them for any length of time and you might find yourself presently going round and round with them until you whirled yourself out of existence, like the gyrating maiden in the fairy tale."

In this type of grinding machine one mill stone rotates on a fixed stone. The cacao nib falls from a hopper through a hole in the centre of the upper stone and, owing to the manner in which grooves are cut in the two surfaces in contact, is gradually dragged between the stones. The grooves are so cut in the two stones that they point in opposite directions, and as the one stone revolves on the other, a slicing or shearing action is produced. The friction, due to the slicing and shearing of the nib, keeps the stones hot, and they become sufficiently warm to melt the fat in the ground nib, so that there oozes from the outer edge of the bottom or fixed stone a more or less viscous liquid or paste. This finely ground nib is known as "ma.s.s." It is simply liquified cacao bean, and solidifies on cooling to a chocolate coloured block.

[Ill.u.s.tration: SECTION THROUGH GRINDING STONES.]

This "ma.s.s" may be used for the production of either cocoa or chocolate.

When part of the fat (cacao b.u.t.ter) is _taken away_ the residue may be made to yield cocoa. When sugar and cacao b.u.t.ter are _added_ it yields eating chocolate. Thus the two industries are seen to be inter-dependent, the cacao b.u.t.ter which is pressed out of the ma.s.s in the manufacture of cocoa being used up in the production of chocolate.

The manufacture of cocoa will first be considered.

(_i_) _Pressing out the excess of b.u.t.ter._

The liquified cacao bean or "ma.s.s," 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.

[Ill.u.s.tration: A CACAO PRESS.

Reproduced by permission of Messrs. Lake, Orr & Co., Ltd.]

If "ma.s.s" be put into a cloth and pressed, a golden oil (melted cacao b.u.t.ter) oozes through the cloth. In practice this extraction of the b.u.t.ter is done in various types of presses. In one of the most frequently used types, the ma.s.s 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 "ma.s.s" is only gently pressed at first, but as the b.u.t.ter 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 b.u.t.ter 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 b.u.t.ter, whilst the cocoa press-cake taken out usually contains only 25 to 30 per cent. The expressed b.u.t.ter 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.

[Ill.u.s.tration: 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._