All About Coffee, William H. Ukers [short story to read .txt] 📗
- Author: William H. Ukers
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In the dry method, the husks are removed either by hand (threshing and pounding in a mortar, on the smaller plantations) or by specially constructed machinery, known as hulling machines.
The Wet Method—Pulping
The wet method of preparation is the more modern form, and is generally practised on the larger plantations that have a sufficient supply of water, and enough money to instal the quite extensive amount of machinery and equipment required. It is generally considered that washing results in a better grade of bean.
In this method the cherries are sometimes thrown into tanks full of water to soak about twenty-four hours, so as to soften the outer skins and underlying pulp to a condition that will make them easily removable by the pulping machine—the idea being to rub away the pulp by friction without crushing the beans.
On the larger plantations, however, the coffee cherries are dumped into large concrete receiving tanks, from which they are carried the same day by streams of running water directly into the hoppers of the pulping machines.
At least two score of different makes of pulping machines are in use in the various coffee-growing countries. Pulpers are made in various sizes, from the small hand-operated machine to the large type driven by power; and in two general styles—cylinder, and disk.
The cylinder pulper, the latest style—suggesting a huge nutmeg-grater—consists of a rotary cylinder surrounded with a copper or brass cover punched with bulbs. These bulbs differ in shape according to the species, or variety, of coffee to be treated—arabica, liberica, robusta, canephora, or what not. The cylinder rotates against a breast with pulping edges set at an angle. The pulping is effected by the rubbing action of the copper cover against the edges, or ribs, of the breast. The cherries are subjected to a rubbing and rolling motion, in the course of which the two parchment-covered beans contained in the majority of the cherries become loosened. The pulp itself is carried by the cover and is discharged through a pulp shoot, while the pulped coffee is delivered through holes on the breast. Cylinder machines vary in capacity from 400 pounds (hand power) to 4,800 pounds (motive power) per hour.
Some cylinder pulpers are double, being equipped with rotary screens or oscillating sieves, that segregate the imperfectly pulped cherries so that they may be put through again. Pulpers are also equipped with attachments that automatically move the imperfectly pulped material over into a repassing machine for another rubbing. Others have attachments partially to crush the cherries before pulping.
The breasts in cylinder machines are usually made with removable steel ribs; but in Brazil, Nicaragua, and other countries, where, owing to the short season and scarcity of labor, the planters have to pick, simultaneously, green, ripe, and over-ripe (dry) cherries, rubber breasts are used.
McKinnon's Guardiola Coffee Drier
The Squier-Guardiola Coffee Drier, With Direct-Fire Heater
The Squier-Guardiola Coffee Drier, With Direct-Fire Heater
BRITISH AND AMERICAN COFFEE DRIERS—GUARDIOLA SYSTEM
There are numerous makes of coffee driers based upon the original invention of José Guardiola of Chocola, Guatemala. In the two illustrated above both direct-fire heat and steam heat may be utilized
The disk pulper (the earliest type, having been in use more than seventy years) is the style most generally used in the Dutch East Indies and in some parts of Mexico. The results are the same as those obtained with the cylindrical pulper. The disk machine is made with one, two, three, or four vertical iron disks, according to the capacity desired. The disks are covered on both sides with a copper plate of the same shape, and punched with blind punches. The pulping operation takes place between the rubbing action of the blind punches, or bulbs, on the copper plates and the lateral pulping bars fitted to the side cheeks. As in the cylinder pulper, the distance between the surface of the bulbs and the pulping bar may be adjusted to allow of any clearance that may be required, according to the variety of coffee to be treated.
Disk pulpers vary in capacity from 1,200 pounds to 14,000 pounds of ripe cherry coffee per hour. They, too, are made in combinations employing cylindrical separators, shaking sieves, and repassing pulpers, for completing the pulping of all unpulped or partially pulped cherries.
Fermentation and Washing
The next step in the process consists in running the pulped cherries into cisterns, or fermentation tanks, filled with water, for the purpose of removing such pulp as was not removed in the pulping machine. The saccharine matter is loosened by fermentation in from twenty-four to thirty-two hours. The mass is kept stirred up for a short time; and, in general practise, the water is drawn off from above, the light pulp floating at the top being removed at the same time. The same tanks are often used for washing, but a better practise is to have separate tanks.
Some planters permit the pulped coffee to ferment in water. This is called the wet fermentation process. Others drain off the water from the tanks and conduct the fermenting operation in a semi-dry state, called the dry fermentation process.
The coffee bean, when introduced into the fermentation tanks, is enclosed in a parchment shell made slimy by its closely adhering saccharine coat. After fermentation, which not only loosens the remaining pulp but also softens the membranous covering, the beans are given a final washing, either in washing tanks or by being run through mechanical washers. The type of washing machine generally used consists of a cylindrical tub having a vertical spindle fitted with a number of stirrers, or arms, which, in rotating, stir and lift up the parchment coffee. In another type, the cylinder is horizontal; but the operation is similar.
Drying
The next step in preparation is drying. The coffee, which is still "in the parchment," but is now known as washed coffee, is spread out thinly on a drying ground, as in the dry method. However, if the weather is unsuitable or can not be depended upon to remain fair for the necessary length of time, there are machines which can be used to dry the coffee satisfactorily. On some plantations, the drying is started in the open and finished by machine. The machines dry the coffee in twenty-four hours, while ten days are required by the sun.
The object of the drying machine is to dry the parchment of the coffee so that it may be removed as readily as the skin on a peanut; and this object is achieved in the most approved machines by keeping a hot current of air stirring through the beans. One of the best-liked types, the Guardiola, resembles the cylinder of a coffee-roasting machine. It is made of perforated steel plates in cylinder form, and is carried on a hollow shaft through which the hot air is circulated by a pressure fan. The beans are rotated in the revolving cylinder; and as the hot air strikes the wet coffee, it creates a steam that passes out through the perforations of the cylinder. Within the cylinder are compartments equipped with winged plates, or ribs, that keep the coffee constantly stirred up to facilitate the drying process. Another favorite is the O'Krassa. It is constructed on the principle just described, but differs in detail of construction from the Guardiola, and is able to dry its contents a few hours quicker. Hot air, steam, and electric heat are all employed in the various makes of coffee driers. A temperature from 65° to 85° centigrade is maintained during the drying process.
When thoroughly dry, the parchment can be crumbled between the fingers, and the bean within is too hard to be dented by finger nail or teeth.
Hulling, Peeling, and Polishing
The last step in the preparation process is called hulling or peeling, both words accurately describing the purpose of the operation. Some husking machines for hulling or peeling parchment coffee are polishers as well. This work may be done on the plantation or at the port of shipment just before the coffee is shipped abroad. Sometimes the coffee is exported in parchment, and is cleaned in the country of consumption; but practically all coffee entering the United States arrives without its parchment.
Peeling machines, more accurately named hullers, work on the principle of rubbing the beans between a revolving inner cylinder and an outer covering of woven wire. Machines of this type vary in construction. Some have screw-like inner cylinders, or turbines, others having plain cone-shaped cores on which are knobs and ribs that rub the beans against one another and the outer shell. Practically all types have sieve or exhaust-fan attachments, which draw the loosened parchment and silver skin into one compartment, while the cleaned beans pass into another.
Polishers of various makes are sometimes used just to remove the silver skin and to give the beans a special polish. Some countries demand a highly polished coffee; and to supply this demand, the beans are sent through another huller having a phosphor-bronze cylinder and cone. Much Guadeloupe coffee is prepared in this way, and is known as café bonifieur from the fact that the polishing machine is called in Guadeloupe the bonifieur (improver). It is also called café de luxe. Coffee that has not received the extra polish is described as habitant; while coffee in the parchment is known as café en parché. Extra polished coffee is much in demand in the London, Hamburg, and other European markets. A favorite machine for producing this kind of coffee is the Smout combined peeler and polisher, the invention of Jules Smout, a Swiss. Don Roberto O'Krassa also has produced a highly satisfactory combined peeler and polisher.
For hulling dry cherry coffee there are several excellent makes of machines. In one style, the hulling takes place between a rotating disk and the casing of the machine. In another, it takes place between a rotary drum covered with a steel plate punched with vertical bulbs, and a chilled iron hulling-plate with pyramidal teeth cast on the plate. Both are adjustable to different varieties of coffee. In still another type of machine, the hulling takes place between steel ribs on an internal cylinder, and an adjustable knife, or hulling blade, in front of the machine.
Sizing or Grading
The coffee bean is now clean, the processes described in the foregoing having removed the outer skin, the saccharine pulp, the parchment, and the silver skin. This is the end of the cleaning operations; but there are two
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