Chapter III · CEREAL PRODUCTS
Reading edition
FLOUR
Sometimes a cheaper or inferior grade of flour is substituted for one of higher quality, and even a different kind of flour may be substituted, as corn meal in wheat flour, or wheat in rye flour. Alum may be added by millers to cover up traces of bad flour, and by bakers to make the bread white when a bad or cheap flour is being used. Copper sulfate also may be added to improve the appearance. Occasionally rye flour is made from rye upon which ergot has developed. Stannous chlorid and potassium carbonate are added to ginger cake to give the same color to the product made of molasses and a poor grade of flour as that made from good flour and honey.
ALUM
Wynther Blyth Method.—Add a little water to the sample and macerate. Soak pieces of gelatin in the solution and leave for a half day, remove the gelatin and dip the pieces in a mixture of equal volumes of a fresh tincture of logwood and a saturated solution of ammonium carbonate. The gelatin strips will turn blue if alum is present.
Bell & Carter Method.—Make a fresh 5 per cent tincture of logwood in methyl alcohol. Dampen about 10 grams of the flour with water and add 1 cc. of the logwood tincture and the same quantity of a saturated solution of ammonium carbonate. Pure flour gives a pinkish color which fades to buff or brown. The presence of alum produces a lavender or bluish tint which becomes more distinct as it dries.
COPPER SULFATE
This adulterant may be detected in either flour or bread, by soaking the flour or bread in a dilute solution of potassium ferrocyanid acidulated with acetic acid. If copper be present a purplish or reddish-brown coloration will be produced.
SUBSTITUTED FLOURS
Vogel’s Method.—Make a mixture of alcohol (70 per cent), 95 parts, hydrochloric acid 5 parts. Treat a sample of the flour in a test tube with this reagent. Shake well. Heat to boiling and allow to settle. A colorless fluid shows the flour to be pure, a straw-colored tint indicates the presence of gruffs with bran, an orange-yellow proves the presence of corn-cockle flour, a flesh-colored liquid indicates the presence of ergot, while a green color indicates buckwheat flour.
Corn Meal in Wheat Flour
Kraemer claims to be able to detect as small amount as 5 per cent of maize in wheat flour, by the following test.—Mix a gram of the flour with 15 cc. of good glycerin, and heat to boiling for a short time. If corn meal is present, there will be an odor like that of pop corn.
Wheat in Rye Flour
Kleeburg recommends the following test.—A little of the flour is mixed on a piece of common window glass or microscope slide, with sufficient water (at 45° C.) to float the flour particles. Spread the mixture out over the glass, and press another glass down upon it. When wheat flour is present, white spots will be seen, and if the glasses are slid upon each other the spots will pull out into threads, and the thicker and longer they are the more wheat flour there is present.
Ergot in Rye Flour
Boettger gives the following chemical test for ergot.—Heat 10 to 15 minutes with an equal quantity of ether, adding a few crystals of oxalic acid. When ergot is present a reddish color develops.
Another Method.—Bul. 51, Bureau of Chem.
Digest 20 grams of the suspected flour, with boiling alcohol, till no more color is extracted. Add 1 cc. of sulfuric acid (1 : 3), and if ergot is present the solution will be colored red.
BREAD
ALUM
Moisten a piece of the bread with water, and then with a logwood solution (5 grams logwood digested in 100 cc. of alcohol). If alum is present the bread will become lavender blue in two or three hours. Pure bread would have a red-brown tint. To prove the presence of alum, the blue color must be permanent at the temperature of boiling water. (The logwood used in this test must be pure.)
Blyth’s Test.—Macerate 150 grams of the sample for 45 or 50 hours in a couple liters of water; after straining through muslin, evaporate to a small volume over a low flame. Immerse a strip of gelatin in this liquid, and then in a logwood solution (same as in last test), and if alum is present it will acquire the lavender color.
If the bread in either of these tests is sour, the following modification (Vanderplanken) must be made. Reduce 15 grams of the sample to a paste with water and some pure chlorid of sodium, adding 10 drops of a fresh alcoholic solution of logwood, after which add 5 grams of pure potassium carbonate. Mix well, and after washing with 100 cc. of water into a vessel allow to settle. If alum is present the liquid will soon become reddish-violet, and if not present it will be blue.
COPPER SULFATE
See Test for Copper Sulfate in Flour
GINGER CAKE
Tin may be detected by the method for heavy metals under meat.