How Heat or Fuel Value is Measured. — It was stated (pp. 28 and 86) that the human body could be compared 366 THE FUEL VALUE OP FOODS 357 with a steam engine, i.e. the burning of the fuel foods in the body produced the ability to do work. The quantity of heat that fuel food is capable of giving off is termed the fuel value of that food. Energy has been defined as the ability to do work. Since heat is energy, the fuel value of foods shows, in part, their nutritive value. If the quantity of heat that is produced by burning a food is measured, the meas- urement indicates the quantity of energy that the food is capa- ble of giving to the body. Heat cannot be measured by weight or length, but by the change in temperature which it produces in a given weight of a certain material. The heat unit is not a pound or yard, but a Calorie, or a definite quantity of heat, which, when applied to materials, will produce change of tem- perature in those materials. If the temperature of one pound 1 of water: is 70° Fahrenheit, 1 and it is desired to increase the temperature of that water to 74° Fahrenheit, a certain quantity of heat will have to be applied. It has been found that the quantity of heat required to raise the temperature of one pound of water through any four de- grees of the Fahrenheit scale is practically the same, i.e. the quantity of heat required to raise the temperature of one pound of water from 32° to 36° F. is about the same as the quantity of heat that must be applied to raise the temperature of one pound of water from 60° to 64° F. The unit of meas- urement of heat is taken as the quantity of heat required to raise the temperature of one pound of water through about 4°F. i Note to the Teacher. — The avoirdupois system of measurement and the Fahrenheit scale of temperature are used in this text. It is be- lieved by the author that less than ten per cent of all pupils taking this course will enter college. Hence, the use of the measurements that are more in keeping with the pupils' practical needs. For the small minority who will enter college, a thorough drill in the metric system is urged. The following formula gives the necessary information for changing from the Fahrenheit to the Centigrade scale : Subtract 32 and multiply by f . - 358 THE PLANNING AND SERVING OP MEALS The Calorie, 1 used for food calculation, is approximately the quantity of heat required to raise the temperature of one pound (pint) of water through 4° F. If one pint of water were placed Fig. 86. — Illustrating the amount of heat represented by one Calorie. * over a lighted burner and heated until it increased four de- grees in temperature, approximately one Calorie of heat would have been applied to the water. (See Fig. 86.) How the Fuel Value of a Food Material is Measured. — Scientists have worked with care to obtain accurate data for the measurement of the heat produced by foods burning in the body. The data accepted to-day differ from those given by Eubner some years ago. 2 1 gram protein yields 4 Calories 1 gram fat yields 9 Calories 1 gram carbohydrate yields 4 Calories Expressing grams approximately in ounces, these data become : 1 ounce of protein yields 113 Calories 1 ounce of fat yields 255 Calories 1 ounce of carbohydrate yields 113 Calories 1 I.e. greater Calorie, distinguished from the lesser calorie by the capi- tal C 2 See " Chemistry of Foods and Nutrition," by Henry C. Sherman, Ph. D., p. 125, Physiological Fuel Values. THE FUEL VALUE OF FOODS 359 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 used. Flour. — The fuel content of flour is (see United States Department of Agriculture Bulletin No. 28, p. 58, All Analyses Average) :

AI-modernized reading of the original text

How Heat or Fuel Value is Measured. — It was stated (pp. 28 and 86) that the human body could be compared THE FUEL VALUE OF FOODS 357 with a steam engine, i.e. the burning of the fuel foods in the body produced the ability to do work. The quantity of heat that fuel food is capable of giving off is termed the fuel value of that food. Energy has been defined as the ability to do work. Since heat is energy, the fuel value of foods shows, in part, their nutritive value. If the quantity of heat that is produced by burning a food is measured, the measurement indicates the quantity of energy that the food is capable of giving to the body. Heat cannot be measured by weight or length, but by the change in temperature which it produces in a given weight of a certain material. The heat unit is not a pound or yard, but a Calorie, or a definite quantity of heat, which, when applied to materials, will produce change of temperature in those materials. If the temperature of one pound 1 of water: is 70° Fahrenheit, 1 and it is desired to increase the temperature of that water to 74° Fahrenheit, a certain quantity of heat will have to be applied. It has been found that the quantity of heat required to raise the temperature of one pound of water through any four degrees of the Fahrenheit scale is practically the same, i.e. the quantity of heat required to raise the temperature of one pound of water from 32° to 36° F. is about the same as the quantity of heat that must be applied to raise the temperature of one pound of water from 60° to 64° F. The unit of measurement of heat is taken as the quantity of heat required to raise the temperature of one pound of water through about 4°F. i Note to the Teacher. — The avoirdupois system of measurement and the Fahrenheit scale of temperature are used in this text. It is believed by the author that less than ten per cent of all pupils taking this course will enter college. Hence, the use of the measurements that are more in keeping with the pupils' practical needs. For the small minority who will enter college, a thorough drill in the metric system is urged. The following formula gives the necessary information for changing from the Fahrenheit to the Centigrade scale : Subtract 32 and multiply by f . - The Calorie, 1 used for food calculation, is approximately the quantity of heat required to raise the temperature of one pound (pint) of water through 4° F. If one pint of water were placed [illustration: Fig. 86. — Illustrating the amount of heat represented by one Calorie.] * over a lighted burner and heated until it increased four degrees in temperature, approximately one Calorie of heat would have been applied to the water. (See Fig. 86.) How the Fuel Value of a Food Material is Measured. — Scientists have worked with care to obtain accurate data for the measurement of the heat produced by foods burning in the body. The data accepted to-day differ from those given by Rubner some years ago. 2 1 gram protein yields 4 Calories 1 gram fat yields 9 Calories 1 gram carbohydrate yields 4 Calories Expressing grams approximately in ounces, these data become : 1 ounce of protein yields 113 Calories 1 ounce of fat yields 255 Calories 1 ounce of carbohydrate yields 113 Calories 1 I.e. greater Calorie, distinguished from the lesser calorie by the capital C 2 See " Chemistry of Foods and Nutrition," by Henry C. Sherman, Ph. D., p. 125, Physiological Fuel Values. THE FUEL VALUE OF FOODS 359 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 used. Flour. — The fuel content of flour is (see United States Department of Agriculture Bulletin No. 28, p. 58, All Analyses Average) :

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