The adulterants commonly used are: chicory, peas, beans, peanuts, and pellets of roasted wheat flour, rye, corn, or barley.
Fat globules are always present in pure coffee; their presence may be shown by the fact that imitation coffee sinks in water, while pure coffee floats.
Chicory is the most frequently used adulterant; it is added for flavor and to produce a darker infusion, thus giving the impression of greater strength. It is perfectly harmless and as a drink is actually preferred by some people. Its detection is comparatively easy. Chicory grains are dark, gummy, soft, and bitter; coffee grains are hard and brittle; a small amount put in the mouth will demonstrate the difference. Chicory will often adhere to the wheels of a coffee grinder, clogging them on account of its gummy consistency.
When a sample of adulterated coffee is thrown in water the pure coffee floats and leaves the water unstained; chicory sinks almost instantly, coloring the water, while peas and beans sink more slowly but also color the water.
Peas and beans are also detected by the polished appearance of the broken or crushed grains in marked contrast to the dull surface of crushed coffee.
The presence of peas, beans, rye, wheat, bread crumbs, and allied substances may be shown by the fact that they all contain starch.
Make a ten per cent infusion of the suspected coffee; filter it, and decolorize the solution by boiling it with a piece of animal charcoal. Test the decolorized solution by slowly adding a few drops of the "potassium-iodide-iodine solution," directions for preparing which were given under heading of "Tea." A resulting blue color will indicate the presence of starch.
COCOA AND CHOCOLATE.—The adulterants of these substances are generally harmless, as they usually consist of flavoring extracts, sugar, starch, flour, and animal fats. No tests other than flavor, consistency, and smoothness need be considered. Good cocoa and chocolate should be slightly bitter, with a pleasant characteristic odor and taste; they should have a smooth, even consistency and be free from grit or harsh particles.
CANNED AND BOTTLED VEGETABLES AND FRUITS.—In general, acid substances, such as tomatoes and fruits, should not be canned in tin, as the action of the acid tends to dissolve the tin. It is better, therefore, to purchase these articles in glass.
After opening the can the odor and appearance of the contents should be noted. The odor should be clean and fresh, and the slightest trace of any sour, musty, or disagreeable smell should cause the rejection of the food. The appearance should be clean, with no mold; the consistency and color of the fruit or vegetables should be uniform throughout. If the color is brighter than that of a similar article when canned at home, the presence of artificial coloring matter must be suspected. The brilliant green of some brands of peas, beans, or Brussels sprouts is produced by the addition of the salts of copper. This may be proved by leaving the blade of a penknife in the contents of the can for a short time; if copper is present it will be deposited on, and discolor, the blade.