DAIRY PRODUCTS

217

(6) Prepare a test solution of methylene blue by mixing 5 cc of saturated
alcoholic solution with 5 cc of 40-per cent formaldehyde and 190 cc of water.
Add 1 cc of this solution to 20 cc of milk in a test-tube, and place the tube
in a water bath at 45°. Cover the liquid with a layer of paraffine oil to
exclude the air. Repeat the test on a heated sample of milk. It will take
about 20 minutes for the unheated milk to decolorize while the heated sample
will require considerably more time.

Condensed Milk.—" Condensed " milk is made by evaporating
either whole or skimmed milk under reduced pressure and adding
cane sugar. " Evaporated" milk does not contain cane sugar.
The Federal standard provides that in evaporated milk there
shall be not less than 34.3 per cent solids, including fat, that the
fat content must be at least 7.8 per cent and that it must not be
made up to this minimum by adding butter oil.1 The composi-
tion of three commercial brands of evaporated milk is given in the
following table:2

TABLE XVI.—COMPOSITION OF EVAPORATED MILK

1

Sample
Water
Fat
Lactose
Protein
Ash

1
70.75
9.42
9.75
8.44
1.54

2
70.90
8.35
10.37
7.86
1.62

3
72.11
8.69
9.66
7.52
1.54

1

The methods of analysis of condensed and evaporated milk
are similar to those described for raw milk, except in the
determination of cane sugar and of lactose.

Preparation of Sample: (a) Unsweetened.—Dilute 40 gm of the homo-
geneous sample with 60 gm of water and make the mixture uniform by
pouring from one beaker to another.

(6) Sweetened.—If the can is cold, place it in water at about 35° until
the temperature of the contents becomes uniform. Open, scrape out all the
milk adhering to the interior of the can and mix by transferring the contents
to a dish sufficiently large to permit stirring thoroughly to make the whole
mass homogeneous. Weigh 100 gm into a 500-cc volumetric flask and,
make up to the mark with water. If the milk will not dissolve completely,
weigh out each portion for analysis separately.

lFood Insp. Decision, 131 (1911).
*Ind. Exp. Sta. Bull, 134 (1909).

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