222

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and shako vigorously and (continue, io shake during cooling, to prevent the
separation of fat and water. Preserve in a eool plan-.
Moisture.—This is a variable quantity i" but tor, the moisture
content ranging from 5 to 25 per cent, but it. averages about 16
per cent. Most of the states have laws regulating the maximum
amount allowed. For the determination, dry sand or jinbefttos
is used in the evaporating dish to increase the effective surface
and thus increase the rate of the drying, unless the dried butter
sample is to be used for the indirect determination of fat, in
which ease the sample is placed in the clean dish. There is
danger of oxidizing the fat if it is subjected to prolonged heating.
Determination of Moisture.—'Place about 2 gin of butter in a dish having
a flat bottom and containing asbestos fiber or sand, the dish and contents
having been dried at 100°, cooled and weighed. Weigh aeeurately, then
dry the fat for one hour at l(K)°t coed in the desireator and weigh. Itepaat
the drying, cooling and weighing hourly until the* weight, is eotmtant to the
third decimal. Calculate the per cent of water in the wimple, Preserve
the dried sample for the fat determination.
Fat.—The fat may be determined either directly, an in milk
analysis, or indirectly by weighing the nolidn left after extracting
the fat with ether or petroleum ether.
Determination of Fat: Direct Method.-—Tht* wimple of wat.er-frw* fat
obtained in the moisture determination in used, ttemove the asbestos
fiber or sand containing the fat front the aluminium dish to an alundum cup
or paper capsule for the extraction apparatus of Fig. 41, tilting anhydrous
ether to rinse out the last traces of fat. Place in the extraction apparatus
nnd thoroughly extract with ether, free from alcohol and water. (See
page 147 for details of the use. of the extractor.) Heeover the ether by dis-
tilling it on a steam bath or electric hot plate, cooling the vnpor by means of
a glass condenser. Dry the flask and fat ut 100", cool, and weigh. Repeat
the drying, weighing each hour until the weight is constant to the third
decimal. Calc.ulatc the per cent of fat in the butter.
lntlire,ct Method,-— Prepare a Oooch filter, dry At HX)* and weigh. Use the
sample of butter which was dried without aslxwtos or Hand in the? moisture
determination. Dissolve this in anhydrous, alcohol-free ether or anhydrous
petroleum ether and pass through the filter. Wash with the solvent until
free from fat. Dry at 100° and weigh, ('iiicuhite the fat by difference.
Casein or Curd.—The amount of curd in good butter varies
from 0.4 to 0.9 per cent. Any coxiHidornhitt amount of butter-
milk left in the butter causes a rapid d<*vdoprn<*nt of protein
decomposition products which impair the flavor of the butter.
The casein may be determined by the Kjeldahl or dunning