FLAVORING EXTRACTS—Vanilla.—This may be wholly or in part the extract of the Tonka bean or may be made from a chemical substance known as vanillin. The best practical working tests as to its purity are the price, taste, and odor. The distinctive odor and taste of vanilla are characteristic and cannot be mistaken.[8]
Lemon.—This extract is often made from tartaric or citric acid. They may be tested for as follows: to a portion of the extract in a test tube add an equal volume of water to precipitate the oil; filter, and add one or two drops of the filtrate to a test tube full of cold, clear limewater; if tartaric acid is present a precipitate will fall to the bottom of the tube. Filter off this precipitate (if present) and heat the contents of the tube; if citric acid is present it will precipitate in the hot limewater.
Footnote.—Dr. Baker wishes to acknowledge her indebtedness to the following authorities and the volumes mentioned for many helpful suggestions. Pearman and Moore, "Aids to the Analysis of Foods and Drugs"; Albert E. Leach, "Food Inspection and Analysis"; Francis Vacher, "Food Inspector's Hand Book."
FOOTNOTES:
[4] The presence of aniline dyes may be detected by mixing a portion of the suspected sample with enough water to make a thin paste. Wet a piece of white wool cloth or yarn thoroughly with water and place it with the paste in an agate saucepan. Boil for ten minutes, stirring frequently. If a dye has been used the wool will be brightly colored; a brownish or pinkish color indicates the natural coloring matter of the fruit or vegetable.—Editor.
[5] A little vinegar added to heated cream or milk produces in the curd a distinct orange color if an aniline dye has been used to make the cream look "rich." The curd will be brown if annatto or caromel has been used. If pure, the curd will be white.—Editor.
[6] This acid must be used with great care; no portion of it should ever come in contact with the skin or clothing.
[7] These acids must be used with great care. They should never be allowed to come in contact with the skin or clothing.
[8] Add a little sugar-of-lead solution to the suspected extract; true vanilla extract will give a yellowish-brown precipitate and a pale, straw-colored liquid. If the extract is artificial, the addition of the lead solution will have little or no effect.—Editor.