IMPORTANCE OF BALANCED DIET 



81 



What is left after the ether evaporates? Foods that are 

 abundant in fat usually will leave a clear spot on thin paper 

 when the food is applied to it. 



Try this test on several fatty foods. 



Record the results in your notebook 1 . 



Experiment 57. How is milk pasteurized? 



Secure two bottles of equal size. Place the two bottles in 

 a dish of water and boil for at least twenty minutes. This 

 will kill all bacteria present in the bottles. Plug the mouths 

 of the bottles with absorbent cotton and stand them aside 

 to cool. Put some raw milk into a vessel and heat to about 

 145 F. Keep stirring the milk with a thermometer and 

 keep the milk at this temperature about thirty minutes. 

 Pour the pasteurized milk into one of the sterilized bottles 

 and plug it with fresh absorbent cotton. Cool it with running 

 water. Put an equal amount of raw milk into the other 

 sterilized bottle and plug with fresh absorbent cotton. Put 

 them aside and examine them from time to time. 



\Yhich milk turns sour first? Why is milk pasteurized? 

 Record the results in your notebook. 2 



OTHER INVESTIGATIONS WHICH YOU CAN MAKE 



1. Keep a record of the foods you eat each meal for 

 three days. Check your diet for the following: 



proportions of the various food nutrients 

 vitamin content 

 mineral content 

 amount of water 

 entire amount of food 

 What improvements can you make in your diet ? 



2. Prepare lists of common foods rich in 

 carbohydrates 



proteins 

 vitamins 

 minerals 



3. Make a study of the relative costs of the foods in 

 the lists compiled in the preceding problem. 



4. Examine a drop of milk under the microscope. 



5. Study the methods used in caring for milk in your 

 community. 



READINGS WHICH WILL HELP ANSWER THE 

 PROBLEM QUESTIONS 



Chemists have analyzed matter, both living and 

 lifeless, and they tell us that there are ninety-two 

 different elements which combine in various ways to 

 form all the different kinds of materials in the uni- 

 verse. The bodies of living things, with few excep- 

 tions, are composed of combinations of about twelve 

 of these ninety-two elements. The composition of the 

 human body is approximately as follows: 



ELEMENT 



Potassium 



Sulphur 



Sodium 



Chlorine 



Magnesium 



Iron 



PER CENT 

 IN BODY 

 0.35 



0.2S 

 0.15 

 0.15 

 0.05 

 0.004 



Thus we see that the body of man is composed of 

 common elements of the earth. 



How many classes of food substances are there? 

 The foods we eat are composed of six classes of food 

 substances, namely, carbohydrates, fats and oils, pro- 

 teins, mineral matter, water, and vitamins. 



Carbohydrates are chemical compounds made from 

 three elements : carbon, oxygen, and hydrogen. Sugars 

 and starch are carbohydrates and are found in the 

 bodies of plants and animals. We obtain these food 

 nutrients chiefly from potatoes, bread, rice, and ripe 

 fruits. 



Fats and oils are made of the same chemical elements 

 as carbohydrates. They differ from carbohydrates in 



CARBO- 

 HYDRATES'. U.N 

 FftT:O.I 



WATER.; 



RROTEIN.J.l 

 : 1.0 



WATER. 35.3 

 PROTFin: 9.3. 

 FAT: 1.3 

 CARBO- 

 HYDRATES: 5 J.I 



ASH= I.I 



BREAD 



ASM: 1,0 



PROTON: 11-9 



-WATER: sa.o 



WATER: 82. fc 



PROTEIN: IT.* 

 FAT: 0.4 



ASH: i. a 



CHOP 



FISH 



WATER: 8M.4 



--PROTEIN -.an 



FAT: 0.5 

 ABO- 



HYDRATES: m.a 



FAT; 33.0 



WATER'. 13.0 



PROTfiN: |.o 



APPLE 



BUTTER 



FIG. 122. WHAT OUR FOODS ARE MADE OF 



that the elements are present in different proportions. 

 They are our best energy-giving foods because they 

 combine with oxygen more easily than carbohydrates 

 and proteins do. Butter, milk, lard, oleomargarine, 

 nuts, and food preparations made from nuts are our 

 principal sources of fats and oils. 



Proteins are always made of the elements carbon, 

 oxygen, hydrogen, and nitrogen and ofttimes have in 

 them smaller quantities of sulphur, phosphorus, or 

 iron. Lean meat, fish, eggs, milk, beans, peas, and 

 bread are our principal sources of proteins. 



In addition to the nutrients (carbohydrates, fats, 

 and proteins) our bodies must be supplied with ade- 

 quate amounts of minerals and water. Minerals are 

 especially needed in the making of bones, teeth, and 



