Part 11 (1/2)
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 rus.h.i.+ng 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.