THE MANUFACTURE OF COCOA AND CHOCOLATE
Early Methods in the Tropics
As the cacao bean is grown in tropical countries, it is there that we must look for the first attempts at manufacturing from it a drink or a foodstuff. The primitive method of preparation was very simple, consisting in roasting the beans in a pot or on a shovel to develop their flavor, winnowing in the wind, and then rubbing the broken shelled beans between stones until quite fine. What’s interesting is that when you grind the cacao bean on a hot tropical day you do not produce a powder but a paste. This is because half the cacao bean consists of a fat which is liquid at 90° F., a temperature which is reached in the shade in tropical countries. This paste was then made into small rolls and put in a cool place to set. This is how the early unsweetened drinking chocolate was made. This is the method, which Elizabethans, who ventured into the tangled forests of equatorial America, found first found native preparing the drink; and this is the method they brought home to Europe. In the tropics these simple processes are followed to this day, but in Europe they have undergone many variations and refinements. When a cacao bean was ground with the original stone tools, the brittle roasted bean is reduced to a paste. A stone, shaped like a rolling-pin, is being pushed to and fro over a concave slab, on which the smashed beans have already been reduced to a paste of a doughy consistency. Workmen used to roast the cacao beans in an iron kettle over a furnace and they had to stir the beans to keep them from burning. After roasting the workers would next sift and free the roasted kernels (which when broken into fragments are called “nibs”) from their husks or shell. Then the workers would pound the shell-free nibs in an iron mortar. This was followed by grinding the nibs on a hard smooth stone with an iron roller. The grinding is performed over a chafing-dish of burning charcoal, as it is necessary, for ease of grinding, to keep the paste in a liquid condition.
Early European Manufacture
The conversion of these small scale operations into the early factory processes occurred around 1768. A certain atmosphere of dreamy intellectuality is associated with coffee, so that the roasting of it is felt to be a romantic occupation. The same poetic atmosphere surrounded the manufacture of drinking chocolate in the early days: the writers who revealed the secrets of its preparation were conscious that they were giving man a new aesthetic delight and the subject is treated lovingly and lingeringly. In Germany the first chocolate factory was erected at Steinhunde in 1756, under the patronage of Prince Wilhelm, whilst in America the well-known firm of Walter Baker and Co. began in a small way in 1765. From the methods adopted in these factories have gradually developed the modern processes. As the early stages in the manufacture of cocoa and of chocolate are often identical, the processes which are common to both are first described, and then some individual consideration is given to each.
Arrival at the Factory
The cacao is largely stored in warehouses, from which it is removed as required. It has remarkable keeping properties, and can be kept in a good store for several years without loss of quality. Samples of cacao beans in glass bottles have been found to be in perfect condition after thirty years. Some factories have stores in which stand thousands of bags of cacao drawn from many ports round the equator. There is something very pleasing about huge stacks of bags of cacao seen against the luminous white walls of a well-lighted store.
Sorting the Beans
As all cacao is liable to contain a little free shell, dried pulp (often taken for twigs), threads of sacking and other foreign matter, it is very carefully sieved and sorted before passing on to the roasting shop. In this process curios are occasionally separated, such as palm kernels, cowrie shells, shea butter nuts, good luck seeds and “crab’s eyes.” The essential part of one type of machine which accomplishes this sorting is an inclined revolving cylinder of wire gauze along which the beans pass. The cylinder forms a continuous set of sieves of different sized mesh, one sieve allowing only sand to pass, another only very small beans or fragments of beans, and finally one holding back anything larger than single beans (e.g., “cobs,” that is, a collection of two or more beans stuck together). This machine with its shaking sieves and blast of air makes a great clatter and fuss. It produces, however, what the manufacturers desire a clean bean sorted to size.
Roasting the Beans
As with coffee so with cacao, the characteristic flavor and aroma are only developed on roasting. The aroma of cacao is chiefly due to an amazingly minute quantity (0.0006 percent) of linalool, a colourless liquid with a powerful fragrant odor, a modification of which occurs in bergamot, coriander and lavender. Everyone notices the aromatic odor which permeates the atmosphere round a chocolate factory.
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 coke 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. Quality control personnel may take 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 shell is brittle and quite free from the cotyledons or kernel. The kernel has become glossy and friable and chocolate brown in color, and it crushes readily between the fingers into small angular fragments (the “nibs” of commerce), giving off during the breaking down a rich warm odor of chocolate.
Removing the Shells
It has been stated that it was formerly the practice not to remove the shell. This is incorrect, the more usual practice from the earliest times has been to remove the shells, though not so completely as they are removed by the efficient machinery of today. The removal of the shell, 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 shell because they offer a greater surface to the air and are lighter than the compact little lumps or “nibs” which are left behind. This illustrates the principle of all shelling or husking machines.
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 shell readily to part company, but it is important to remember that the smaller the pieces of shell 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 passing 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.
Separating the Germs
About one percent. 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 assumed to be less digestible than the nib. They are separated by being passed through revolving gauze drums, the holes in which are the same size and shape as the germs, so that the germs pass 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 (shell) and nails (germ) by sieving through a grid-iron, he would find that not only the nails passed through but also some sawdust and fine shavings. So in the above machine the finer nib and shell pass through with the germ. This germ mixture, known as “smalls” is dealt with in a special machine, whilst the larger nib and shell are conveyed to the chief winnowing machine. In this machine the mixture is first sorted according to size and then the nib and shell separated from one another. The mixture is passed 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 shell from the nib is now effected by a powerful current of air, the large nib falling against the current, whilst the shell is carried with it and drops into another and nails (germ) by sieving through a grid-iron, he would find that not only the nails passed through but also some sawdust and fine shavings. So in the above machine the finer nib and shell pass through with the germ. This germ mixture, known as “smalls” is dealt with in a special machine, whilst the larger nib and shell are conveyed to the chief winnowing machine. In this machine the mixture is first sorted according to size and then the nib and shell separated from one another. The mixture is passed 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 shell from the nib is now effected by a powerful current of air, the large nib falling against the current, while the shell 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. This is the process in essence—to follow the various partially separated mixtures of shell 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 shell, 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 shell, a standard which can only be maintained by continuous vigilance. A battery of horizontal grinding mills, by which the cacao nibs are ground to paste (Mr. Cadbury Bros., Bournville.) The shell, 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.
We have seen that the beans are roasted separately according to their kind and country so as to develop in each its characteristic flavor. The pure nib is now blended in proportions which are carefully chosen to attain the result desired.
Grinding the Cacao Nibs to Produce Mass
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-colored 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. 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 center 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 “mass.” It is simply liquified cacao bean, and solidifies on cooling to a chocolate colored block. This “mass” may be used for the production of either cocoa or chocolate. When part of the fat (cacao butter) is taken away the residue may be made to yield cocoa. When sugar and cacao butter are added it yields eating chocolate. Thus the two industries are seen to be inter-dependent, the cacao butter which is pressed out of the mass in the manufacture of cocoa being used up in the production of chocolate. The manufacture of cocoa will first be considered.
Pressing out the excess of Butter
The liquified cacao bean or “mass,” simply mixed with sugar and cooled until it becomes a hard cake. It produces a fine rich drink, 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, while the cocoa press-cake taken out usually contains only 25 to 30 percent of butter, while the cocoa press-cake taken out usually contains only 25 to 30 percent. All that it is necessary to do to obtain cocoa from the press cake is to powder it.
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 person’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.
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.
The cocoa powder is taken to the packing rooms. Here the tedious weighing by hand has been replaced by ingenious machines, which deliver with remarkable accuracy a definite weight of cocoa into the paper bag which lines the tin. The tins are then labelled and packed in cases ready for the grocer.
THE MANUFACTURE OF CHOCOLATE
Since the great improvements of the steam engine, it is astonishing to what a variety of manufactures this useful machine has been applied: yet it does not a little excite our surprise that one is used for the trifling object of grinding chocolate. Since eating-chocolate is produced by mixing sugar and cacao nib, with or without flavoring materials, and reducing to a fine homogeneous mass, the principles underlying its manufacture are obviously simple, yet when we come to consider the production of a modern high-class chocolate we find the processes involved are somewhat elaborate.
Preparing the Nib or Mass
The nib is obtained in exactly the same way as in the manufacture of cocoa, the beans being cleaned, roasted and shelled. The roasting, however, is generally somewhat lighter for chocolate than for cocoa. The nibs produced may be used as they are, or they may be first ground to “mass” by means of mill-stones as described above.
Mixing in the Sugar
Some makers use clear crystalline granulated sugar, others disintegrate loaf sugar to a beautiful snow-white flour. The nib, coarse or finely ground, is mixed with the sugar in a kind of edge-runner or grinding-mixer, called a mélangeur. The mélangeur consists of two heavy mill-stones which are supported on a granite floor. This floor revolves and causes the stationary mill-stones to rotate on their axes, so that although they run rapidly, like a man on a “joy wheel,” they make no headway. The material is prevented from accumulating at the sides by curved scrapers, which gracefully deflect the stream of material to the part of the revolving floor which runs under the mill-stones. Thus the sugar and nib are mixed and crushed. As the mixture usually becomes like dough in consistency, it can be neatly removed from the mélangeur with a shovel. The operator rests a shovel lightly on the revolving floor, and the material mounts into a heap upon it.
Grinding the Mixture
The mixture is now passed through a mill, which has been described as looking like a multiple mangle. The object of this is to break down the sugar and cacao to smaller particles. The rolls may be made either of granite (more strictly speaking, of quartz diorite) or of polished chilled cast iron. Chilled cast iron rolls have the advantage that they can be kept cool by having water flowing through them. A skilled operator is required to set the rolls in order that they may give a large and satisfactory output. The cylinders in contact run at different speeds, and, as will be seen in the diagram, the chocolate always clings to the roll which is revolving with the greater velocity, and is delivered from the rolls either as a curtain of chocolate or as a spray of chocolate powder. It is very striking to see the soft chocolate-coloured dough become, after merely passing between the rolls, a dry powder—the explanation is that the sugar having been more finely crushed now requires a greater quantity of cacao butter to lubricate it before the mixture can again become plastic. The chocolate in its various stages of manufacture, should be kept warm or it will solidify and much time and heat (and possibly temper) will be absorbed in remelting it; for this and other reasons most chocolate factories have a number of hot rooms, in which the chocolate is stored whilst waiting to pass on to the next operation. The dry powder coming from the rolls is either taken to a hot room, or at once mixed in a warm mélangeur, where curiously enough the whole becomes once again of the consistency of dough. The grinding between the rolls and the mixing in the mélangeur are repeated any number of times until the chocolate is of the desired fineness. Whilst there are a few people who like the clean, hard feel of sugar crystals between the teeth, the present-day taste is all for very smooth and highly refined chocolate; hence the grinding operation is one of the most important in the factory, and is checked at the works at Bournville by measuring with a microscope the size of the particles. The cost of fine grinding is considerable, for whilst the first breaking down of the cacao nibs and sugar crystals is comparatively easy, it is found that as the particles of chocolate get finer the cost of further reduction increases by leaps and bounds. The chocolate may now proceed direct to the molding rooms or it may first be conched.
We now come to an extraordinary process which is said to have been originally introduced to satisfy a fastidious taste that demanded a chocolate which readily melted in the mouth and yet had not the cloying effect which is produced by excess of cacao butter. In this process the chocolate is put in a vessel shaped something like a shell (hence called a conche), and a heavy roller is pushed to and fro in the chocolate. Although the conche is considered to have revolutionized the chocolate industry, it will remain to the uninitiated a curious sight to see a room full of machines engaged in pummelling chocolate day and night. There is no general agreement as to exactly how the conche produces its effects—from the scientific point of view the changes are complex and elusive, and too technical to explain here—but it is well known that if this process is continued for periods varying according to the result desired from a few hours to a week, characteristic changes occur which make the chocolate a more mellow and finished confection, having more or less the velvet feel of chocolat fondant.
Art is shown not only in the choice of the cacao beans but also in the selection of spices and essences, for, whilst the fundamental flavor of a chocolate is determined by the blend of beans and the method of manufacture, the piquancy and special character are often obtained by the addition of minute quantities of flavorings. The point in the manufacture at which the flavor is added is as late as possible so as to avoid the possible loss of aroma in handling. The flavors used include cardamom, cassia, cinnamon, cloves, coriander, lemon, mace, and last but most popular of all, the vanilla pod or vanillin. Some makers use the choice spices themselves, others prefer their essential oils. Many other nutty, fragrant and aromatic substances have been used; of these we may mention almonds, coffee, musk, ambergris, gum benzoin and balsam of Peru. The English like delicately flavored confections, whilst the Spanish follow the old custom of heavily spicing the chocolate. In ancient recipes we read of the use of white and red peppers, and the addition of hot spices was defended and even recommended on purely philosophical grounds. It was given, in the strange jargon of the Peripatetics, as a dictum that chocolate is by nature cold and dry and therefore ought to be mixed with things which are hot.
Small quantities of cacao butter will have been added to the chocolate at various stages, and hence the finished product is quite plastic. It is now brought from the hot room (or the mélangeur or the conche) to the molding rooms. Before molding, the chocolate is passed through a machine, known as a compressor, which removes air-bubbles. This is a necessary process, as people would not care to purchase chocolate full of holes. As in the previous operations, every effort has been made to produce a chocolate of smooth texture and fine flavor, so in the molding rooms skill is exercised in converting the plastic mass into hard bars and cakes, which snap when broken and which have a pleasant appearance. Well-molded chocolate has a good gloss, a rich color and a correct shape. The most important factor in obtaining a good appearance is the temperature, and chocolate is frequently passed through a machine (called a tempering machine) merely to give it the desired temperature. A suitable temperature for molding, according to Zipperer, varies from 28° C. on a hot summer’s day to 32° C. on a winter’s day. As the melting point of cacao butter is about 32° C, it will be realized that the butter is super-cooled and is ready to crystallize on the slightest provocation. Each mold has to contain the same quantity of chocolate. Weighing by hand has been abandoned in favour of a machine which automatically deposits a definite weight, such as a quarter or half a pound, of the chocolate paste on each mold. The chocolate stands up like a lump of dough and has to be persuaded to lie down and fill the mold. This can be most effectively accomplished by banging the mold up and down on a table. In the factory the method used is to place the molds on rocking tables which rise gradually and fall with a bump. The diagram will make clear how these vibrating tables are worked by means of ratchet wheels. Rocking tables are made which are silent in action, but the molds jerkily dancing about on the table make a very lively clatter, such a noise as might be produced by a regiment of mad cavalry crossing a courtyard. During the shaking-up the chocolate fills every crevice of the mold, and any bubbles, which if left in would spoil the appearance of the chocolate, rise to the top. The chocolate then passes on to an endless band which conducts the mold through a chamber in which cold air is moving. As the chocolate cools, it solidifies and contracts so that it comes out of the mold clean and bright. In this way are produced the familiar sticks and cakes of chocolate. A similar method is used in producing “Croquettes” and the small tablets known as “Neapolitans.” Other forms require more elaborate molds; thus the chocolate eggs, which fill the confectioners’ windows just before Easter, are generally hollow, unless they are very small, and are made in two halves by pressing chocolate in egg-shaped molds and then uniting the two halves. Chocolate cremes, caramels, almonds and, in fact, fancy “chocolates” generally, are produced in quite a different manner. For these chocolats de fantaisie a rather liquid chocolate is required known as covering chocolate. It is prepared in exactly the same way as ordinary eating chocolate, save that more butter is added to make it flow readily, so that in the melted condition it has about the same consistency as cream. The operations so far described are conducted by men, but the covering of cremes and the packing of the finished chocolates into boxes are performed by girls. Covering is light work requiring a delicate touch, and if, as is usual, it is done in bright airy rooms, is a pleasant occupation.