CEREAL PRODUCTS
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.