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Roasting Coffee

( Originally Published 1900 )



AN old adage, familiar to many, yet quite changed, or rather, impossible to use now in its original sense, runs that " Good wine needs no bush." If we reverse and slightly alter the thought we may come to the conclusion that good coffee does need good roasting. Roasting is without doubt the most important part of the coffee dealer's business. You may buy the very best quality and yet sell most inferior coffee, though it must not be thought that good roasting can make inferior coffee into a fine quality. Still it is quite certain that some inferior coffee, if carefully and correctly roasted, will make a more palatable beverage than very fine coffee badly and incorrectly roasted. On the subject of to what extent coffee should be roasted there is a great difference of opinion. Even here in our own country there is by no means one standard, but in other countries, and those where far larger quantities are consumed, there is not so much diversity. One point, the most important point that decides how highly a coffee should be roasted, is its growth. And here we may say at once that, such being the case, namely that different growths require different degrees of roasting, those machines are of no real value which have been patented after so much labour, and in many respects are most excellent, but which are so constructed that just before the roast is finished a warning bell is rung. For unless the dealer is to confine himself to one quality and growth only, he will want constantly to alter the settings or to ignore the warning. Speaking generally, there is no question that we in this country roast to a much lighter degree than in any other, This is a curious fact, and some have argued that it is largely owing to this cause that our consumption is so much smaller than in those countries where the roasting is done to a higher, in fact much higher, degree. It must, however, be borne in mind that small though our consumption is, it is mostly made up of the finest growths with the most delicate flavour, and even in countries where high roasting is the rule, the finer grades are usually less done. If coffee is roasted highly this delicate flavour is destroyed and it would be needless to continue to use the fine qualities. Moreover, coffee that is highly roasted will lose its aroma quicker, in fact, will change its quality by developing a fresh flavour which is by no means palatable if kept any length of time ; and as it is generally the custom here for the housewife to purchase it once a week, or even at longer intervals, it is evident that on this account alone it should be only sufficiently done and on no account burnt. In France and Germany roasting is done to a considerable degree higher than here, while in Scandinavia it is-according to our own standards—quite burnt. In America it is mostly roasted higher than with us, and in addition a glaze is added of which we shall have to speak later. In Brazil coffee is roasted probably higher than in any other country, certainly than any country where the consumption is large, and it is very heavy indeed there. In nearly all these countries, however, certainly in Brazil, the coffee is consumed almost immediately after roasting. Climate and custom have perhaps much to do with the advantages or otherwise of highly-roasted coffee ; as an example, the writer was once spending a holiday in Switzerland, where he could not get a cup of good coffee, and indeed had not had one since he left home, in spite of all the supposed virtues of " coffee on the Continent." On the top of a high pass he and his party all agreed that they at last had found a good cup. On asking to be allowed to see from what it was made, he was shown an extremely badly roasted sample, some berries burnt and others pale, and the raw was a description which in this country is never used on account of its common and objectionable flavour.

The following account gives a scientific account of what takes place in the process of roasting ----

Coffee undergoes essential chemical changes in the process of roasting. In the raw or natural state the coffee-bean is tough and horny in structure, and entirely devoid of the appearance, character, and peculiar aroma that so distinguishes it in the roasted condition, and by which it is best known to the public. The testa or investing membrane of the raw bean has a layer of long cells with a peculiar pitted structure, containing a crystaline substance chemically termed caffeine, and another known as caffeic, or tannic acid, while the inner substance consists of an assemblage of vesicles of an angular form, the cavities of which include in the form of little drops a considerable quantity of a highly aromatic oil technically termed caffeone, on the presence and amount of which the fragrance and active principles of the coffee depends, and by which its commercial value in the roasted state is estimated. The existence of this " coffee oil " makes itself known in a striking manner by roasting ; being driven out of the beans by the intense heat, it is partially volatilized and, together with other products of the roasting, produces the characteristic aroma peculiar to roasted coffee, an odour possessed by no other known substance. In the operation of roasting, the beans swell up and open at the furrow by the liberation of the gases within their substance, their weight decreasing, but volume increasing in proportion to the extent to which the operation is carried, developing the aromatic oil and liberating at the same time a portion of the caffeine from its combination with the caffeic, or tannic acid. The amount of this aromatic oil contained in coffee varies from 8 to 13 per cent., at least one-half of which is lost by evaporation during the roasting process, so that it may prove a paying experiment to attempt to collect it, especially in large establishments where large quantities of coffee are roasted and several pounds of this valuable oil are dissipated daily, which would no doubt find a ready market at a good profit for the making of liqueurs, or medicinal use.

Before being roasted coffee also contains from 6 to 8 per cent. of sugar, which after roasting is reduced to as low as 1 per cent. and sometimes even to zero, from which it would appear that the description of sugar present in the raw coffee suffers destruction during roasting, which, however, is not the case, as in the process of roasting the saccharine matter in the raw bean is converted into caramel. A change in the fat of the raw coffee is also brought about by the roasting, for where ether extracts only some four to five parts of fat from the raw coffee beans, it readily extracts double that quantity from the roasted beans. So striking is this fact that Von Bibra has even credited the roasting process with the production of fat, whereas the action is only mechanical in bursting the fat-cells of the raw bean, thereby rendering the fat accessible to the solvent action of the ether.

The operation of roasting also tends to make coffee soluble in boiling water, as when raw coffee is perfectly exhausted by means of boiling water, it yields up only 25 per cent. which passes into solution, while roasted coffee, on the other hand, when completely exhausted by means of boiling water, yields readily upwards of 40 per cent. of soluble matter, proving that in actually using coffee as a beverage, we are not in the habit of making anything like a complete extraction, as only some 10 to 12 per cent. of the active principles of the coffee passes into the liquid.

Such being a few facts about what takes place during roasting, what is the best system to adopt ? What is the best fuel ? The great object to aim at is to obtain a berry which is equally roasted inside and outside. To this end electricity would give the most perfect roast, for it has a penetrating power unknown to any other. A machine has been invented and proved most excellent in operation, but the cost, not only of the electricity, but of " wear and tear," and consequently renewal of plant is at present prohibitive from a commercial point of view. Of the two other kinds, gas or coke, it has been demonstrated, times without number, that the latter gives much better results when roasting on a large scale. For roasting in this way there is nothing better than the old malleable iron cylinder, fitted with gauze ends—a most important item, as the liberated gases are thus allowed to escape. The cylinder revolves over a clear coke fire, and is internally fitted with an ingenious arrangement of eccentric bearings by which means the coffee is constantly kept moving, being thrown from side to side in order to secure a thorough roast of the whole contents and not a part properly roasted and a part not thoroughly done. By an arrangement in the handle a small scoopful can be withdrawn in order that the operator may know the exact moment at which to empty the cylinder. Too great haste in the roasting, or a few degrees of heat too much will char the berries and spoil its flavour. On he other hand, too little heat and consequently too much time taken in roasting will spoil the flavour in another way. It will thus be seen that coffee-roasting is an art, which cannot be learnt in a few hours, or even days, but one which requires not only time, but also care and attention. When, however, the roasting is completed there remains the cooling process, and this is almost as important as the roasting. Where there is sufficient room the cylinder is drawn back and opened, by means of the slide, directly over a tray, or box, with a woven wire bottom, through which air is forced either by a blast or a rotary fan. The importance of cooling rapidly is due to the fact that the moment having arrived when the coffee is roasted, if simply turned into a tray and allowed to cool gradually, the chemical changes would continue to be developed, and thus the correct flavour would be destroyed, whereas by rapid cooling (the quicker the better) this development is checked, and the coffee remains roasted to the exact point at which it was withdrawn from the cylinder. There are, of course, very few grocers who have accommodation sufficient for such machinery—and therefore have to be content with a small gas roaster. For this purpose a machine can be obtained either with the flame under, or within the cylinder. In either case the gas is mixed with a blast of air upon the principle of the bunsen burner. In some a sheet of talc is inserted by means of which the coffee can be watched as it is roasted ; this, however, is not really as satisfactory as the arrangement of a sampling rod in the handle, for the talc becomes blurred by steam and smoke. There is yet one other system, namely by roasting, in small 1/2 lb. or 1-lb. cylinders as can often be seen in shop windows. The latter is of course the most expensive, for not only has allowance to be made for the loss of room, but there is in addition the time taken up and the operator's wages. There comes in as well the difficulty of quick cooling, and if this can be overcome there is no question that not only a better roast, because a more perfect aroma, can be obtained from the small cylinder than from either of the large ones. Great care must, however, be taken that each roast is done to the same degree, otherwise if several roasts are bulked together a mottled appearance will result together with inferior infusion.

Without such quick cooling, a better roast can often be obtained from the large coke roaster, operated by an experienced workman, than from the small cylinders, especially where the operator has not been properly trained. The roasting in small cylinders, in full view of customers, was at one time a very excellent advertisement, but the novelty has largely worn off, the practice having been adopted by at least one grocer in nearly every town. The aroma of roasting is undoubtedly still a means of drawing attention to the article and often leads to sales being made. Alas, that such should be the case, for it would be much more satisfactory if coffee were looked upon as a necessity, in fact an article of daily consumption as bread and, certainly, as tea.

The above has referred exclusively to the ordinary roasting, namely that which produces a berry in colour varying from pale cinnamon to a dark chestnut and, as has been said, the finer the coffee the paler it should be roasted. There is also the " French " roast, which is obtained by simply adding a small quantity of soft sugar to the roast some little time before the operation is completed, say about three parts done. The limit of sugar allowed by the excise for this is 3 per cent. only, but that is quite sufficient for the required purpose. Coffee wanted for mixing with chicory is mostly so treated ; it is also largely done to produce " black " or " after-dinner " coffee ; in this case the coffee has also to be roasted to a much higher degree. Such treatment is not really necessary for the making of black coffee, but it is often adopted. Mention was made just now of excise regulations. It may not be generally known that public roasters are all under excise supervision. Indeed all roasters are liable to inspection, as it is illegal to add any substance (except sugar as above) while roasting. The reason is that the addition would add weight to the " returns " and thus defraud the revenue. Gases have been known in this country, and it is possible that it is still done to a small extent, but the penalty, if found out, is very heavy, and tends to check those who might otherwise act fraudulently. In some parts of the Continent and largely in America it is a common thing to coat coffee with a resinous or glutinous compound known as " glazing." This is done partly to hide light berries in the roast and partly to make a more handsome and showy appearance, an advantage where the sale is generally of the whole berry, and not as is mostly the case here, in the ground state. To conclude, we may say that fresh grinding is really more important than fresh roasting. A grocer should be prepared to grind freshly for each customer and mills attached to electric motors are now so prevalent that such can easily be the case. At the same time, it would be better to encourage the householder to grind it for himself. Coffee should not be coarsely ground ; if so, the infusion will take much longer to make and in fact will not give as good a result as when ground to a powder.



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