As gluten is only very sparingly soluble in boiling water, in the usual way of making coffee the flesh-formers are thrown away with the dregs; the addition of a little soda to the water partly prevents this waste.
The various components in one pound of coffee will be—
| oz. | grs. | |
| Water | 1 | 407 |
| Caffeine, or theine | 122 | |
| Casein, or cheese | 2 | 35 |
| Aromatic oil | 1½ | |
| Gum | 1 | 192 |
| Sugar | 1 | 17 |
| Fat | 1 | 402 |
| Potash | 280 | |
| Woody fibre | 5 | 262 |
| Mineral matter | 1 | 31 |
The part roasted is the albumen, which is of a hard, horny consistence; and Lindley remarks that it is probable that the seeds of other plants of this or the stellate order, whose albumen is of the same texture, would serve as a substitute. This would not be the case with those with fleshy albumen.
Coffee loses in weight by roasting, but gains in bulk in proportion to the heat applied.
Payen found the following amount of nitrogen in 100 parts dried:
| nitrogen. | ash. | |
| Martinique | 2·46 | 5·00 |
| Bourbon | 2·54 | 4·66 |
| Mocha | 2·49 | 7·84 |
The coffee from Martinique lost 11·58 per cent. of its weight by drying. This description of coffee also afforded the following results:
| Unroasted. | Slightlyz reddened. | Chesnut brown. | Brown. | |
| Loss in roasting | — | 15 per cent. | 20 per cent. | 25 per cent. |
| Increase in bulk | — | 1·3 times | 1·53 times | — |
| Extract | 40 per cent. | 37 per cent. | 37·1 per ct. | 39·25 per ct. |
| Insoluble residue | 48·5 “ | — | — | — |