Chapter 71
The mixer does not blend the various coffees any more surely than a good roaster cylinder will do it, but treats batches of much larger size.
This means saving a great amount of labor that would be necessary for putting the desired quant.i.ty of component coffees into each individual roaster.
A proper installation of green coffee machinery requires various bins of ample capacity, and bucket elevators by which the coffee can be sent without manual labor from one operation to another. In modern plants, all the bins and elevators are constructed of metal. The separator, with its bins and elevator, may be installed independently of the rest of the plant, the graded coffee being all bagged up again and treated as new raw stock--some of it to be held for later use, or perhaps sold again unroasted. The milling machine and the mixer, however, are usually so placed and connected that the coffee can be sent from one to the other, and to the roaster feed hoppers, without any manual labor.
When the roaster sells his product in package form ready for the consumer, he will have a packaging department in which are grinding, weighing, labeling, and packing machines and equipment. In some of the more progressive plants, particularly in the United States, all the packing units are incorporated in one machine, so that the different steps in the work are carried on automatically and in one continuous operation.
[Ill.u.s.tration: GREEN-COFFEE-MIXER CONNECTIONS
To operate at full capacity, without using the story above as well as below the mixer, requires a bucket elevator and three bins, each holding a full mixing batch. The above diagram explains this setting. The mixed coffee in the discharge bin is either drawn out into bags or sent by an elevator to a milling machine or direct to the coffee roasters. A batch ready for mixing can always be acc.u.mulated in the feed bin while the previous batch is being mixed or discharged.
The fan is usually hung to the ceiling over the mixer as indicated, and connected to the suction box by a 1-in. round pipe. The fan outlet can be carried directly out-of-doors; but the dusty discharge is objectionable in most installations, and this pipe is usually carried to a dust collector from the top of which the roof outlet is connected.]
The efficient roaster-executive equips his entire plant with approved labor-saving devices. In the better establishments, the coffee is carried along by mechanical conveyors through all the operations from the first cleaning machine to the final packaging.
_Separating_
As already mentioned, a machine frequently found in wholesale plants is the separator, or grader. This apparatus, which is the same in principle in all countries, but varies in size and form according to local requirements, consists of a series of perforated screens. The perforations differ in size; and as the coffee is shaken on them, the small beans drop through the holes, the larger ones pa.s.sing across the screen and dropping into a receptacle or chute ready for the next operation. The screens are made to grade the beans into large and small peaberry; large, medium, and small flat beans; brokens; and other commercial sizes. The average separator will grade fifteen to twenty bags of coffee in an hour.
[Ill.u.s.tration: Green-coffee-milling machine having a capacity of forty bags of green coffee per hour; with sifter, feed-pipe suction, and a final separate suction at the discharge hopper]
[Ill.u.s.tration: Green-coffee separator without fan; with feed elevator, discharge chutes, and motor drive. View of right-hand side and feed end]
[Ill.u.s.tration: GREEN-COFFEE SEPARATING AND MILLING MACHINES]
_Milling_
Milling machines, for cleaning the green coffee, operate on practically the same principle the world over, varying in capacity and details of construction. A popular type used in the United States has two metal cylinders, one set within the other, and revolving in opposite directions. The inner cylinder is ribbed with f.l.a.n.g.es, and the outer one is lined with wire cloth. As these cylinders revolve, the beans pa.s.s between them rubbing against themselves and the rough sides of the cylinders. This action serves to remove dirt and other foreign matter that may be clinging to the beans, and also gives them an attractive polish. An exhaust fan sucks away the dirt milled off in the process.
This type of machine will mill about forty bags of green coffee in an hour.
_Mixing or Blending Green Coffee_
Most roasters blend the different types of coffee while green. Some blend them after they have been roasted separately. When blended before roasting, the coffees are mixed by a machine built especially for that purpose. The mixing machine in general use in all countries consists of a large metal cylinder which, in wholesale operations, is revolved by the factory's general power plant or by a separate motor. The cylinder is equipped on the inside with sets of reverse-screw mixing f.l.a.n.g.es that tumble the beans around until they are thoroughly blended; and there is usually a fan attachment to remove dust. This operation serves also to smooth down and to polish the surfaces of the beans, which adds to the style of the coffee when roasted. The average blending machine will mix from ten to twenty bags of coffee at a time. The actual mixing requires less
_Roasting by Coal, c.o.ke, Gas, and Electricity_
Coffee is roasted commercially in cylinder or ball receptacles revolving in heated chambers, the degree of heat reaching about 420 Fahr. The cylinder type of roaster is invariably used in the United States; while both the cylinder and the ball types are popular in England, France, Germany, Holland, and other foreign countries.
[Ill.u.s.tration: AN ENGLISH FOUR-MACHINE GAS COFFEE-ROASTING PLANT
The equipment includes three Morewood indirect-flame, and one quick direct-flame machines]
Each roasterman has his own opinion about the fuel that gives the best result, and throughout the world the choice lies between anthracite coal, c.o.ke, and gas; though hard wood is frequently used in countries where other fuels are not available or not economical. Electric heat has been tried for commercial roasting in Germany (1906), in England (1909), and in the United States (1918); but the experimenters have always found the cost of electric fuel to be prohibitive in compet.i.tion with coal and gas. An electric roaster was demonstrated at the Food Conservation Show in New York, in 1918, at a time when the federal government was urging the necessity of conserving coal as a war economy measure. The inventor claimed that his machine would reduce roasting cost, improve the flavor and the aroma, and maintain a constant and easily controlled heat. He declared also that when roasted in his devices, less coffee was required for brewing.
An expert coffee-roasting-machinery man who has been working on the development of a practical electric roaster says that if it were possible to bake the coffee in an oven, just as the baker does his bread, the fuel cost would then compare favorably with that of gas or coal. It is because the heat chamber must have an exhaust to release the chaff and smoke that the use of electricity to replace the heat loss proves prohibitive when compared with coal or gas.
In all types of coal and c.o.ke burning roasters, the cylinders are heated by a fire underneath; while in gas roasters, the flame may be underneath or within the cylinder itself. Roasters in which the heat is within the cylinder are known as direct-flame or inner-heated machines. All three systems are used in the United States and Europe.
_Facts About Coffee Roasting_
The modern commercial roasting outfit is as near fool-proof as human genius has been able to devise. The more advanced types are almost automatic in operation, and are designed to insure uniformity of roasts.
In such machines the green coffee is conveyed to the roasting cylinder by means of bucket elevators, which pour the beans into a feed hopper.
From the feed hopper, the coffee is dumped through the opening in the front head-piece into the cylinder. The cylinder is perforated, and has inside f.l.a.n.g.es which keep tossing the coffee about while the cylinder revolves, so that the coffee will not burn during the roasting process.
[Ill.u.s.tration: GERMAN GAS COFFEE-ROASTING PLANT EQUIPPED WITH IDEAL-RAPID MACHINES]
To roast coffee by coal or c.o.ke usually requires from twenty-five to thirty minutes, depending on the moisture-content of the beans; whether they are spongy or flinty; whether a light, medium, or dark roast is desired; and on the skill of the operator. Gas roasting requires from fifteen to twenty minutes. The quicker the roast, the better the coffee, is the opinion of many trade leaders, one of whom[325] says:
It is a growing belief that in roasts of short duration the largest percentage of the aromatic properties is retained. A slow roast has the effect of baking and does not give full development; also, slow roasts seldom produce bright roasts, and they usually make the coffee hard instead of brittle, even when the color standard has been attained.
[Ill.u.s.tration: FRENCH GAS COFFEE-ROASTING PLANT EQUIPPED WITH MODERNE MACHINES]
While coffees of widely varying degrees of moisture require somewhat different treatment, the consensus of opinion is that the best results are obtained from a slow fire at the beginning, until some of the moisture has been driven off, when the stronger application of heat may be given for development. An intense heat in the beginning often results in "tipping", or charring, the little germ at the end, the most sensitive part of the bean.
Scorched beans have been caught at some point in the cylinder, often in a bent f.l.a.n.g.e. Burning on one face, sometimes called "kissing the cheeks", is caused by the too rapid revolution of the cylinder, so that some of the coffee "carries over". In the best practise, crowding of cylinders is avoided; many roasters making it a rule not to exceed ninety percent of the rated capacity of the cylinder.
Those operating gas roasters may effect a fuel economy by running a low grade coffee in the cylinder after the last roast has been drawn and the gas extinguished; five minutes' revolution absorbs the heat and drives off a proportion of moisture. The coffee, which may then be left in the cylinder, requires less time and fuel in the morning, and the roast is finished while the cylinder is warming up. Double roasting brightens a roast, but is a detriment to the cup quality. A dull roasting coffee may be improved by revolving the green coffee in a cylinder without heat for twenty minutes, which has the effect of milling.
The use of a small amount of water upon roasts gives better control by checking the roast at the proper point--the crucial time of its greatest heat; also, it swells and brightens the coffee, and tends to close the outer pores. While the addition of water is open to abuse, few roasters have soaked their coffees enough to offset the natural shrinkage as much as three or four percent. Such practise would result greatly to the detriment of the cup quality.
There is no universal standard for the degree to which coffee should be roasted. In the United States, there are demands for all degrees; from the light roast, in favor in England, to the extremely dark roast in vogue in France, Italy, Brazil, Turkey, and in the producing countries.
The North American trade recognizes these different roasts: light, cinnamon, medium, high, city, full city, French, and Italian. The city roast is a dark bean, while full city is a few degrees darker. In the French roast, the bean is cooked until the natural oil appears on the surface; and in the Italian, it is roasted to the point of actual carbonization, so that it can be easily powdered. Germany likes a roast similar to the French type; while Scandinavia prefers the high Italian roast.
In the United States, the lighter roast is favored on the Pacific coast; the darkest, in the South; and a medium-colored roast, in the Eastern states. The cinnamon roast is most favored by the trade in Boston.
While coffee roasting in the United States usually takes from fifteen to thirty minutes, depending on the fuel and the machine employed, manufacturers of gas machines on the German market claim to roast it in superior fas.h.i.+on in from three and a half to ten minutes.[326] This subject is discussed more in detail in chapter x.x.xIV.
Coffee loses weight during the roasting process, the loss varying according to the degree of roasting and the nature of the bean. Coffee roasters figure, however, that the average loss is sixteen percent of the weight of the green bean. It has been estimated that one hundred pounds of coffee in the cherry produces twenty-five pounds in the parchment; that one hundred pounds in parchment produces eighty-four pounds of cleaned coffee; and that one hundred pounds of cleaned coffee produces eighty-four pounds roasted.
[Ill.u.s.tration: JUMBO COFFEE ROASTER, IN THE ARBUCKLE COFFEE-ROASTING PLANT, NEW YORK
There are four of these machines. The cylinders are twelve feet in diameter, six feet deep, and can roast 5,000 pounds of coffee every half-hour. The hard-coal brick furnace is seen at the left, from which a blower forces the heated air through a pipe into the revolving cylinder of coffee. The coffee is fed from above and is emptied into the cooling pans beneath]
[Ill.u.s.tration: AN EIGHT-CYLINDER GAS COFFEE-ROASTING PLANT
A view of Reid, Murdoch & Co.'s roasting room, Chicago, equipped with Monitor machines]
During the roasting process the coffee undergoes a great chemical change. After it has been in the cylinder a short time, the color of the bean becomes a yellowish brown, which gradually deepens as it cooks.
Likewise, as the beans become heated, they shrivel up until about half done, or at the "developing" point. At this stage, they begin to swell, and then "pop open", increasing fifty percent in bulk.[327] This is when the experienced roasterman turns on all the heat he can command to finish the roasting as quickly as possible.
_"Dry" and "Wet" Roasts_
At frequent intervals, he thrusts his "trier"--an instrument shaped somewhat like an elongated spoon--into the cylinder, and takes out a sample of coffee to compare with his type sample. When the coffee is done, he shuts off the heat and checks the cooking by reducing the temperature of the coffee and of the cylinder as quickly as can be done.