36 



EXPERIMENT 25. EFFECT OF HEAT ON PROTEIDS 



Put the white of a fresh un- 

 cooked egg into a test tube and 

 place the test tube in a beaker of 

 water as shown in Figure 26. 

 Heat the water in the beaker and 

 notice the effect of the heating on 

 the egg. At what temperature 

 does the white thicken and harden 

 or coagulate ? 



Can you explain why boiled 

 milk is less digestible than cold 

 or slightly warmed milk ? 



Are hard boiled eggs digest- 

 ible ? 



FIG. 26. The effect of heat on 

 white of egg. 



EXPERIMENT 26. THE PRESENCE OF WATER IN SOME 

 COMMON FOODS 



Wash an apple and a potato until they are clean, then 

 dry them with a cloth. Weigh each, and place them in an 

 almost cold oven, allowing them to dry out, but not to cook. 

 When they have dried out sufficiently, weigh them again 

 and determine what percentage of their original weight has 

 been lost. Make this experiment with a loaf of bread. 



The loss of weight is due to the evaporation of their 

 water content. 



