668 ■h)}iriit(l of Afjriciilture, Victorin. [10 Nov., 1916. 



COMPARATIVE FOOD VALUES OF DAIRY PRODUCE. 



By R. T. Archer, Senior Dairy Inspector. 



Food is necessary to all organisms for their development and 

 growth, to supply them with heat and energy, to make good the losses 

 resulting from Avear and tear of their mechanism, and to keep them in 

 a state of efficiency. 



The elements of all our animal and vegetable foods are derived from 

 the inorganic earth, air, and water. It is obvious that animals could 

 not live upon inorganic substances or derive nutriment from them, 

 important as such inorganic materials are for many vital processes. 

 The essential parts of animal structui'es are derived from previously 

 organized materials. Most of these organic compounds arise in the 

 vegetable kingdom as comparatively simple substances, and become 

 elaborated into more complex bodies in the vegetable or animal 

 organism. Therefore, it may be said that the constituents of human 

 food, the elements of the human body are derived from the denizens of 

 the earth, air, and water. 



The materials which compose the structures of the man's body are 

 derived from his food, and are in turn composed of inorganic substances 

 to which they can be reduced. The most important of these elements 

 are carbon, hydrogen, oxygen, and nitrogen, which form twenty-nine 

 thirtieths of the entire weight of the body and enter into the construc- 

 tion of every cell. There are other elements which, even though they 

 form but a small portion of the weight of the body, are of prime 

 importance to the proper construction of the various parts of the body, 

 e.g., iron for the blood, phosphorus for brain and nerves. 



The value of a food is estimated by the amount of heat (which is 

 the equivalent of energy) that is generated by a given quantity when 

 oxidized or burnt or consumed, which amounts to the same thing. This 

 is expressed in heat units or calories. A calorie is the amount of heat 

 required to rai.se a kilogram of Avater 1° CVntigrade or 1 lb. of water 

 4° Fahrenheit. 



The purpose for which food is required in the body is — 



1. To build up the body tissue. 



2. To develop heat and energy. 



3. To repair the waste of tissue. 



The principal kinds of nutritiA^e ingredients are protein, fat, carbo- 

 hydrates, and mineral matter or ash. 



There are also present in most kinds of food, Avater, indigestible 



fibre. &^c., AAdiich are called non-nutriments. In comparing the values 



of different food materials for nourishment, they are left out of account. 



The digestible nutrients are divided into four princiiial classes as 



follows : — 



Protein, e.g., albumen fAA^hite of eggs and milk), casein fcurd) 

 of milk; muscle (lean meat) ; gluten of wheat, &c. These 

 are so called nitrogenous foods. Their particiilar function 

 is to build up the cell system and repair Avaste of tissue. 

 They will also produce fat and Avill generate heat or 

 enerffv. 

 Feds, e.a., fat of meat; fat (butter) of milk; oliA'e oil, S:c. 

 These form fatty tissue, not muscle, and generate heal 

 and energy. 



