Coffee affords very little nourishment, and is apt to occasion heat, dryness, stimulation and tremors of the nerves, and for these reasons is thought to occasion palsies, watchfulness, and leanness. Hence it is very plain that it must be pernicious to hot, dry, and bilious constitutions. If moderately used it may be beneficial to phlegmatic persons, but, if drank very strong, or in great quantities, it will prove injurious even to them.
The following remarks on Coffee, were published in London, by a physician.
1st. The raw coffee should be round and small grained, free from dirt and of a light color. It should have no appearance of mouldiness, and be kept quite free from any strong smell. It should not be long kept in sacks with other provisions, as there is no substance more apt to obtain strong and disagreeable odors from the presence of its neighbors. Hum injures it; and Miller even goes so far as to state that a few bags of pepper on board a ship from India upon one occasion spoiled the whole cargo.
2nd. When the grains are large, flat, and of a green color, they should be kept on hand, in a dry situation, a long time before use. Every West India planter knows this fact, although his interest often induces him to send the article to market before it is old and dry enough.
3d. Roasting coffee is by far the most difficult operation of the housekeeper; when carried far enough, an aromatic oil is formed by the heat and forces itself out upon the surface of the grains, giving them a glossy appearance, and an odor which is considered their perfection; yet too little roasting prevents the aroma from appearing, and too much completely volatilizes it, leaving nothing but a flat bitter taste. The heat should be strong and the operation shortened as much as possible without burning the grains. The roaster should be close or well covered all the time, and in order to improve the looks and flavor, a small piece of butter may be added to the coffee, while parching.
4th. When thus prepared, coffee may be preserved for use in large quantities, without losing much of its freshness, provided the vessels containing it be well covered.
5th. An infusion of coffee is better than a decoction, simply because the heat, in the last case, being stronger and more lasting, drives off more of the aromatic oil. It is better, therefore, to grind the coffee very fine, and then to expose it, by means of a bag or strainer, to the action of boiling water, than to boil it any length of time. Heat, though unavoidable, injures the flavor, and the best coffee I remember to have tasted was made by exposing the powder to a pressure of cold water; a tea-spoonful of this extract, thrown into a cup of hot water, was sufficient. It is not a bad method to allow the ground coffee to lie in cold water between meals, and then prepare it by adding hot water. Just in proportion to the continuance of heat, in this and in the last operation, the fragrance disappears, and is replaced by a strong bitter taste, which, according to the experiments of Chenevix, depends upon the presence of tannin (resembling that in tan bark). Roasting, besides forming this bitter substance, deprives the coffee of its nutritious qualities.