In order to find the fuel value of foods, it is necessary to know their composition. For such data _United States Department of Agriculture_ Bulletin No. 28 is a valuable source.
_Flour_.--The fuel content of flour is (see _United States Department of Agriculture_, Bulletin No. 28, p. 58, All a.n.a.lyses Average):
10.6 per cent protein; 1.1 per cent fat; 76.3 per cent carbohydrates.
Then, 1 ounce of flour contains, 0.106 ounce of protein; 0.011 ounce of fat; 0.763 ounce carbohydrates.
The protein in one ounce of flour yields (113 x 0106 =) 11.97 Calories.
[Ill.u.s.tration: FIGURE 83.--COMPARATIVE WEIGHTS OF 100-CALORIE PORTIONS OF FOODS.]
The fat in one ounce of flour yields (255 x 0.011 =) 2.80 Calories. The carbohydrates in one ounce of flour yield (113 x 0.763 =) 86.21 Calories.
Total Calories furnished by 1 ounce of flour are (11.97 + 2.80 + 86.21 =) 100.98.
_b.u.t.ter_.--The fuel content of b.u.t.ter is (see _United States Department of Agriculture_, Bulletin No. 28, p. 54):
1 per cent protein; 85 per cent fat; no carbohydrates.
1 ounce of b.u.t.ter contains 0.01 ounce of protein, 0.85 ounce of fat, and no carbohydrates.
The protein in one ounce of b.u.t.ter yields (0.01 x 113 =) 1.13 Calories.
The fat in one ounce of b.u.t.ter yields (0.85 x 255 =) 216.75 Calories.
Number of total Calories furnished by one ounce of b.u.t.ter is (1.13+216.75=) 217.88.
_Sugar_.--The fuel content of sugar is (see _United States Department of Agriculture_, Bulletin No. 28, p. 65) no per cent protein; no per cent fat; 100 per cent carbohydrates.
1 ounce of sugar contains no protein, no fat, and 1 ounce carbohydrates. 1 ounce sugar yields (113 x 1 =) 113 Calories.
HOW THE WEIGHT OF FOOD MATERIALS PRODUCING 100 CALORIES IS MEASURED.--For practical work in computing the fuel value of foods, it has been found more convenient to reduce all data to terms which express equal fuel value instead of equal weight as in the foregoing paragraph. One hundred Calories is the unit chosen. The weight of a food which, when "burned" in the body, will produce one hundred Calories is the desired data. This weight is termed a _standard portion_ or a _100-Calorie portion_ (see Figures 83 and 84).
From the previous work, it is a simple matter to compute in ounces the quant.i.ty of food materials which will yield 100 Calories.
If 1 ounce of flour yields 100.98 Calories and _x_ represents the number of ounces of flour which will yield 100 Calories, then _x_/1=100/100.98 or _x_=0.99, the number of ounces of flour which yield 100 Calories, _i.e._ a 100-Calorie portion of flour.
If 1 ounce of b.u.t.ter yields 217.88 Calories and _x_ represents the number of ounces of b.u.t.ter which will yield 100 Calories, then _x_/1=100/217.88 or _x_=0.45, the number of ounces of b.u.t.ter which yield 100 Calories, _i.e._ a 100-Calorie portion of b.u.t.ter.
[Ill.u.s.tration: FIGURE 84--100-CALORIE PORTIONS OF FOODS. a, banana, b, b.u.t.ter, c, eggs d, meat; e, bread.]
If 1 ounce of sugar yields 113 Calories and x represents the number of ounces of sugar which will yield 100 Calories, then _x_/1=100/113 or _x_=0.88, the number of ounces of sugar which will yield 100 Calories, _i.e._ a 100-Calorie portion of sugar.
HOW THE FUEL VALUE OF A COMBINATION OF FOOD MATERIAL IS MEASURED.--It is possible to compute the fuel value of a food that is made up of several food materials. To do this one must know or find:
(_a_) Recipe for food.
(_b_) Weight and measure of combustible food materials.
(_c_) Number of Calories yielded by one ounce of each of the combustible foodstuffs.
The recipe for one loaf of bread is:
1 cupful water 1 teaspoonful salt 1 teaspoonful sugar 3 1/2 cupfuls flour 1/2 tablespoonful b.u.t.ter 1/4 cake compressed yeast 1/4 cupful water
By weighing and measuring one finds:
1 pound sugar measures 2 cupfuls 1 pound b.u.t.ter measures 2 cupfuls 1 pound flour measures 4 cupfuls
Then,
1 teaspoonful sugar weighs 0.16 ounce 1/3 tablespoonful b.u.t.ter weighs 0.25 ounce 3 1/2 cupfuls flour weigh 14.0 ounces
(From data of _How the Fuel Value of a Food Material is Measured_.)
1 teaspoonful sugar yields (113 x 0.16 =) 18.08 Calories 1/2 tablespoonful b.u.t.ter yields (217.88 x 0.25 =) 54.47 Calories 3 1/2 cupfuls flour yield (100.98 x 14 =) 1413.72 Calories 1 loaf of bread yields (18.08 + 54.47 + 1413.72 =) 1486.27 Calories
For the practical method of calculating diet (which is more fully treated in Lesson Cx.x.xI), it is convenient to have the 100-Calorie portion of a recipe, or a "made" food.
The 100-Calorie portion of bread is estimated from the result above in the following manner:
Since 1486.27 Calories are yielded by one loaf of homemade bread, then 100 Calories are yielded by (100/1486.27 =) .06 or 6 per cent of a loaf of homemade bread; hence, 1/16 (6 ) or 1 slice of homemade bread yields 100 Calories.
QUESTIONS
Find the number of Calories produced by one ounce of milk.
Find the number of Calories produced by one ounce of egg.
Weigh out 100-Calorie portions of flour, b.u.t.ter, and sugar.
Measure these quant.i.ties, using a cup for the flour, a tablespoon for the b.u.t.ter, and a teaspoon for the sugar.
Compute 100-Calorie portions of milk and the edible portion of eggs, then weigh these portions.
Measure this portion of milk in a cup. How many eggs make a standard portion?
Why are water, salt, and yeast not considered when the fuel value is computed?
Compute the fuel value of 1 pint of Soft Custard.
Find the 100-Calorie portion of Soft Custard.
NOTE.--Forms A and B given on the following pages will be found convenient in recording the results of these calculations.
LESSON CXVII
PLANNING, COOKING, AND SERVING A DINNER