This section is from the book "Elements Of The Theory And Practice Of Cookery", by Mary E. Williams. Also available from Amazon: Elements Of The Theory And Practice Of Cookery; A Textbook Of Domestic Science For Use In Schools.
The amount of fat in milk is indicated by calling it a 4 % milk, or a 5 or 6 % milk, according to the percentage of fat it contains. Most babies cannot digest milk containing more than 4 % of fat. If a baby can digest richer milk, it is well to give it to him. For some babies 7 % milk may be used. In this there is about twice as much fat as protein, the same proportion as in mother's milk. Few cows give 7 % milk. It may be obtained by adding cream to poorer milk, or by using the top part of bottled milk. Formulas calling for such milk are called top-milk formulas.
7 % milk, 7 oz.
Lime-water, 1 oz.
Milk sugar, 3/4 oz.
Water, 12 oz.
This is to be divided into seven bottles, putting a scant three ounces into each bottle.
To obtain 7 % milk from milk containing less than 4 % of fat, you will have to use less than half the bottle. To obtain it from rich Jersey milk you will have to use more than half the bottle. If a doctor orders top-milk formulas, he will see that you have milk of a known fat content and will tell you exactly how much top milk to remove.
The use of skim milk. Lowering the proportion of fat. - Skim milk may be used as the basis of modified milk, or it may be used instead of water to dilute whole milk, when the object is to reduce the fat without reducing the protein and salts. To obtain 4 % milk from 5 % multiply 32 by 5, divide by 4, and subtract 32. This gives us 8, the number of ounces of skimmed milk which must be added to a bottle of whole milk to make 4 % milk.
Multiply the number of ounces in a quart, 32, by the figure representing the fat content. Divide the product by the figure representing the desired fat content, and subtract 32 from the quotient. The resulting figure will be the number of ounces of skimmed milk to be added to the richer whole milk to produce the milk desired.
If the milk comes in a pint bottle, what figure would you use instead of 32? Figure out the reduction of 1 pint of 5 % milk to 4 % milk. How many ounces of 4 % milk can you make out of 2 quart bottles of 5 % milk? How many out of 2 pint bottles? If the formula calls for 18 ounces of milk or less, will it be most economical to use quart or pint bottles? Why? An extra pitcher will be needed for mixing the skim milk and whole milk.
Milk (4 %), 16 1/2 oz.
Malt sugar, 2 tb.
Water (to boil sugar in), 3 oz.
Suppose you have only 5 % milk. To obtain 4 % milk, you must add 8 ounces of skimmed milk to a quart of whole milk, or 4 ounces of skimmed milk to a pint bottle of whole milk. To skim the milk, dip off all the cream with a cream-dipper. The milk should have stood in a cold place at least four hours, so that the cream line is distinct. Stir the skim milk and whole milk together in one pitcher. Measure 16 1/2 ounces and put into the other pitcher. Proceed as with other formulas. Stir the food after filling each bottle, or the barley jelly may settle at the bottom of the pitcher, and the last bottle filled will contain more barley jelly than the others. Do this wherever thick gruel is used.
For school-work it is not necessary to have actual 5 % milk. The method of obtaining 4 % milk from 5 % milk may be practiced with any milk, whatever its fat content.