Brightly colored fruits should excite suspicion; this same dictum applies to all brightly colored jams and jellies, as the colors are usually produced by the addition of carmine or aniline red.
The presence of preservatives, salicylic and boric acids, the benzoates, etc., can only be proved by delicate chemical tests.
SUGAR.—Pure granulated or powdered sugar is white and clean. The presence of glucose should be suspected in sugar sold below the market price; it is perfectly harmless, but has a sweetening power of only about two-thirds that of sugar and is added on account of its cheapness and to increase the bulk.
If sand, dirt, or flour are present they may be detected by observation, or by washing the suspected sample in water; flour will not dissolve, sand will sink, and dirt will discolor the water.
SPICES.—Spices should be bought whole and ground in a spice mill as needed; if this is done, there need be little fear of their impurity, for whole spices are difficult to simulate or adulterate. Ground spices may be adulterated with bark, flour, starches, or arrowroot; these adulterants are harmless, but are fraudulent, as they increase the bulk and decrease the strength. Their actual presences can only be demonstrated by a microscopical or chemical examination.
Peppers.—Black pepper is made from the whole berry; white pepper is made from the same berry with the outer husk removed. The adulterants are usually inert and harmless substances, such as flour, mustard, or linseed oil; their presence is obviated by the use of the whole peppercorns, ground as needed.
Red Pepper.—This may be adulterated with red lead; when pure it will be entirely suspended in water; if a sediment falls it is probably red lead.
Mustard.—Practically all of the adulterants of mustard can only be detected by intricate chemical tests. The presence of turmeric may be detected by the appearance of an orange-red color when ammonia is added to a solution of the sample.
Tomato Catsup.—Artificial dyestuffs are common, giving a brilliant crimson or magenta color. Such catsup does not resemble the natural dull red or brown color of the homemade article.
Preservatives, such as boric, salicylic, or benzoic acids and their salts, are sometimes added. While their presence cannot be condoned, yet they are usually present in small amounts and therefore practically harmless.