DAIRY PRODUCTS 221
extensive there seems to be some evidence to the effect that lower
readings are obtained in this way.
Total solids, ash, total nitrogen and lactose are determined as
with whole milk. A somewhat smaller sample (2 to 3 gm) is
used for the total solids determination. The gravimetric
method for lactose is preferred.
ICE CREAM ;jp<j
Determination of Fat: Rose-Gottlieb Method.—Weigh 4 gm of ice cream || I
(melted by exposure to air, then thoroughly mixed) in a 50-cc beaker, add
3 cc of water and mix with a glass rod. Pour the mixture into a Rohrig
tube and wash the beaker and rod, using 3 cc of water and adding the wash-
ings to the tube. Add 2 cc of concentrated ammonium hydroxide and after
mixing thoroughly, heat in a water bath at 60° for 10 minutes. Add 10 cc
of 95-per cent alcohol and continue as directed on page 206 for the deter-
mination of fat in milk.
BUTTER AND SUBSTITUTES |!
Butter, according to the Federal standards, is the clean, non- |j
rancid product made by gathering, in any manner, the fat of
fresh or ripened milk or cream into a mass containing also a small
portion of other milk constituents, with or without salt, and
which contains not less than 82.5 per cent of milk fat.1 By acts
of Congress, approved Aug. 2, 1886 and May 9, 1902, butter
also may contain added coloring matter.
determine whether or not some foreign oil or fat has been partly
or wholly substituted for butter fat, (b) to determine whether an
excessive amount of milk or water has been incorporated or (c)
to identify "process" butter (butter which has been steamed to
correct rancidity). Adulteration with another fat or steaming
rancid butter changes the microscopical appearance of the
mixture from non-crystalline (as butter fat naturally exists) to
crystalline, the added fat usually having been previously melted.
Preparation of Sample.—Butter is not usually of a homogeneous com-
position but it can be made approximately so by melting and shaking during
solidification. If large quantities of butter are to be sampled, use a butter
sampler. Place 500 gm or more of the sample in a wide-mouth glass
stoppered bottle and warm gently until the entire mass is melted. Stopper
1 U. S. Dept. Agr. Chem. Bull, 64, 37 (1920).