MEATS AND EGGS
Meats are preserved by treating them with potassium nitrate, boric acid,
sulfurous acid, salicylic acid, or benzoic acid. Cheap meat may be
substituted for the more expensive. A few cases of horse meat in mince
meat and sausages have been discovered. Diseased and stale meats have
been found on the market. Canned meats often contain zinc, tin, and
lead, and sometimes even arsenic. Aniline-red or cochineal-carmine may
be added to improve the color of chopped or ground meats. Starch is
sometimes added to sausage and similar meat. Fish and oysters may be
preserved with boric acid or borax.
FRESH AND SMOKED PRODUCTS--PRESERVATIVES
POTASSIUM NITRATE (SALTPETER)
Corned and smoked meats are usually preserved with saltpeter. Since
smoked and cured meats are used in making potted meats, saltpeter is
quite frequently found in the latter. It may be detected by the usual
test for nitrates since no other nitrate is apt to be present, though
one may identify the metal by the qualitative test for potassium.
To test for nitrates treat a little of the meat with 2 or 3 cc. of a 1
per cent solution of diphenylamine in strong sulfuric acid. If a
nitrate is present a deep blue color forms instantly, which is not
obscured by the charring effect of the acid.
BORIC ACID
Pick apart into fine pieces about 25 or 50 grams of the lean meat and
warm with a little water which has a few drops of hydrochloric acid in
it. Soak a piece of turmeric paper in the extract, and if boric acid is
present the paper will be colored rose-red when it is dry. A weak alkali
turns this colored paper olive.
Another method is to burn a piece of the meat to an ash, after being
treated with lime water. Make a solution of the ash and make slightly
acid with hydrochloric acid. Then test with the turmeric paper with the
same results as in the above method.
SULFUROUS ACID
U. S. Dep. Agr., Bureau Chem., Bul. 13, Part 10: Digest 40 or 50 grams
of the meat in hot water, treat with 10 cc. glacial phosphoric acid to
coagulate the proteids. Strain through a cotton bag and transfer the
filtrate to a short-necked flask and distil receiving the first part of
the distillate in a solution of iodin. Boil, and add barium chloride. If
sulfurous acid is present, it will be oxidized to sulfuric acid and
precipitated as barium sulfate by the barium chlorid. More than a mere
trace of the precipitate proves that some sulfite was used to preserve
the meat.
Another method suggested by Kämmerer is to place the meat on paper,
which has been saturated with potassium iodate moistened with dilute
sulfuric acid (1 : 8); nitric oxid must not be present. If sulfurous
acid is present a deep blue color forms at once. A trace of this color
may form after some time with meat that is not fresh, hence this method
cannot be used in examining canned meat.
SALICYLIC ACID
Heat 50 grams of the meat in 50 cc. of water. Add 10 cc. of a strong
solution of glacial phosphoric acid and strain through a cotton bag.
Extract the filtrate with a little ether (about 50 cc.) in a separatory
funnel. Let the ether evaporate spontaneously. Take up the residue with
3 cc. of water, and add one or two drops of a one-half per cent solution
of ferric chlorid. If salicylic acid is present the mixture will be
purple or violet.
Leach makes the same test by slightly acidifying a portion of the lean
meat, then extracting with ether, and evaporating to dryness and testing
the residue with a drop of ferric chlorid solution. A deep violet
coloration is produced if salicylic acid is present.
BENZOIC ACID
_Mohler’s Method._--Prepare a sample as in the test for salicylic acid
by heating 50 grams of the meat in 50 cc. of water. Add 10 cc. of a
concentrated solution of glacial phosphoric acid, and strain through a
cotton bag. Neutralize with sodium hydrate and evaporate to dryness or
to a small volume. After treating with 3 cc. of concentrated sulfuric
acid, heat till white fumes appear. Add 4 or 5 crystals of potassium
nitrate and continue heating until the solution is colorless or nearly
so. When cool dilute with water, add an excess of ammonia, and place in
a narrow vessel like a test tube. Add one or two drops of ammonium
sulfid carefully so that the liquids do not mix. If the surface of the
liquid immediately becomes red, benzoic acid is present.
If this test is not carefully performed, it is worthless, as other
substances give similar results.
Confirm its presence by neutralizing the aqueous solution of the
extracted benzoic acid with sodium hydroxid; concentrate to a very small
volume. Acidify with sulfuric acid. A white flocculent precipitate shows
the presence of considerable benzoic acid.
CANNED MEAT
If in preparing canned meat only fresh meat is used, there is little
need for the use of preservatives, but as considerable smoked and cured
meat is thus used, preservatives may find their way into canned meat.
The same preservatives should be looked for as in fresh and smoked meat
and the same test made for each.
HEAVY METALS
_A. H. Allen’s Method._--About 25 grams of the substance is mixed slowly
with enough strong, pure sulfuric acid to just moisten the mass,
avoiding an excess. Heat on a water-bath for a short time, then raise
the temperature gradually, and maintain till the chlorids seem to be
decomposed. It must not be hot enough, however, to volatilize the
sulfuric acid. Then add 1 cc. of strong nitric acid and heat till red
fumes are given off. Freshly ignited magnesia in the proportion of 0.5
gram for each cc. of sulfuric and nitric acid previously used is now
stirred into the mass and the whole ignited at a dull red heat. This is
best done in a gas-muffle. When cool, moisten the ash with nitric acid
and gently re-ignite, repeating this treatment till the carbon is
entirely consumed. Treat the residue with 8 or 10 drops of strong
sulfuric acid, heat till fumes are given off, cool, boil with water,
dilute to about 100 cc. and saturate with hydrogen sulfid, filter,
examine as follows:
==========================++===========================================
Zinc and iron may be in ||Lead, tin, copper, and calcium, if present,
solution. Add bromine ||will be in the precipitate and residue.
water to destroy hydrogen ||Fuse the mass in a porcelain crucible for
sulfid and to oxidize the ||at least ten minutes with 2 grams each of
iron, boil and add ammo- ||potassium and sodium carbonates and half
nium hydrate in excess, ||as much sulfur. After cooling, boil with
boil again and filter. ||water and filter.
---------------+----------++---------------------------+---------------
The precipitate|Filtrate, ||Residue. Add hydrochloric |The filtrate may
will contain |when blue,||acid and boil as long as |contain tin.
the iron and |proves the||hydrogen sulfid is given |Acidify with
the phosphates.|presence ||off. A few drops of bro- |acetic acid, and
|of nickel.||mine water will complete |if tin is pres-
| ||the oxidation of the |ent a yellow
| ||copper sulfid. Filter, and|precipitate of
| ||add ammonium hydroxid in |stannic sulfid
| ||excess to the filtrate. |will form.
| ||When the filtrate is blue,|
| ||it indicates the presence |
| ||of copper. Acidify the |
| ||filtrate with acetic acid |
| ||and test for lead by |
| ||adding potassium chromate,|
| ||a yellow precipitate being|
| ||formed when it is present.|
---------------+----------++--------------------------+----------------
|I. Heat to|| |
|boiling || |
|and add || |
|potassium || |
|ferrocya- || |
|nid. A || |
|white pre-|| |
|cipitate || |
|or turbi- || |
|dity in- || |
|dicates || |
|_zinc_. || |
===============+==========++==========================+================
FISH SALT DRIED AND OYSTERS
This kind of meat is often preserved with boric acid and borax. They may
be detected by the method given under fresh and smoked meat.
COLORING MATTER
Sausages and other chopped meat preparations, together with corned meat
that has been cured without saltpeter, are often treated with artificial
coloring matter.
Aniline red and cochineal carmine are usually employed for this purpose.
The former may be detected, according to Allen, by picking the meat
apart and treating it with methylated spirit, strain or filter the
extract and take up with water. Then a piece of white wool (nun’s
veiling will do) is immersed in the boiling liquid and, if it is dyed
red, rosaniline is present.
Cochineal-carmine may be detected by the method used by Klinger and
Bujard. Cut up fine about 20 grams of the meat and heat in a water-bath
with water and glycerine mixed in equal parts. If the above coloring
matter is present the liquid will become quite red in color, if not
present a slight yellow color results from this treatment. If a
spectroscope is available this dye is easily recognized.
STARCH
IN SAUSAGE, DEVILED MEAT, AND SIMILAR PRODUCTS
Cracker and bread crumbs are often added to these preparations and their
presence is best detected by examining the amount of starch present. Do
this by boiling some of the sample in water, and when cool adding a drop
or two of iodin reagent. The usual blue color is produced if much
starch is present. If there is only a little starch, it may be necessary
to examine it under the microscope to determine whether the starch is
from the pepper and other spices used or from some cereal.
DISEASED MEAT
_The following method is recommended by Ebers._--Hold a small piece of
the suspected meat over a mixture of 1 cc. hydrochloric acid, 3 cc.
alcohol, and 1 cc. of ether. The formation of ammonium chlorid fumes
shows that decomposition has begun. Do not mistake the fumes of the acid
for those of ammonium chlorid.
HORSE FLESH
IN SAUSAGE AND MINCE MEAT
This sophistication is not common in this country. Horse flesh is
detected by testing for glycogen, which is present in it in larger
quantities than in other meats.
_Courley & Coremon’s Test._--Boil 50 grams of the meat for a half hour
with water, strain, and to a portion of the filtrate add a few drops of
potassium iodid-iodin solution (potassium iodid 0.4 gram; iodin 0.1
gram; water 20 cc.). If considerable horse meat is present the glycogen
will color the liquid dark brown, which disappears on heating, but
returns on cooling.
EGGS
It sometimes happens that one wishes to know the age of eggs without
opening them.
_Delarne’s Test._--Place the egg in a 10 per cent solution of common
salt. Perfectly fresh eggs sink to the bottom. Those remaining
immersed, but suspended in the liquid, are at least three days old,
while those rising to the surface and floating are more than five days
old. The older the egg, the higher it floats and the more it will stand
on end. This test is not applicable to eggs that have been preserved.
Hold the egg between a bright light and the eye, and if the air chamber
is small, and no dark spots but instead a rather uniform rose-colored
tint is seen, the egg is fresh. If the contents appear cloudy and the
air chamber larger, the egg is not fresh. The darker the contents of the
egg the older it is.