5 8 THE CORNELL READING-COURSES 



of the flour, so they raise the whole mass. When the bread is baked the 

 gas is dissipated, the gluten walls of these bubbles are hardened, and 

 little holes remain, filled with air only. The alcohol, too, is driven off 

 by the heat. 



It is very difficult to keep weeds out of the vegetable garden because 

 their seeds are carried to the soil in many ways. When the weeds have 

 sprouted or grown a little, they may be pulled up easily. In the bread- 

 garden we want only yeast to grow, but it is very difficult to insure its 

 growth alone since in the bread garden neither the good plants nor the 

 weeds ever become visible. In no other way does household bacteriology 

 interest the housekeeper so much as when connected with the baking 

 of her bread. 



Compressed yeast-cakes and dry yeast-cakes consist of a mass of yeast 

 plants mixed with some form of starch and pressed into cakes. One yeast- 

 cake may contain one half -billion yeast plants. It should contain only 

 one species of yeast, but oftentimes other plants gain access to the mixture. 

 If a compressed yeast-cake has been kept over a day or two it begins 

 to turn dark and to soften. That is an indication that the yeast plants 

 are dying and that bacteria have gained access to the cake, thus causing 

 decay. The cake should then be discarded, for it will not make good 

 bread. If dough is left too long or if it is kept too warm, the yeast plants 

 become weakened; then the bacteria that may be present grow and pro- 

 duce an acid, making the bread sour. We scald the milk used in making 

 bread in order to destroy the bacteria present. We bake bread for a full 

 hour, or longer if the loaf is very large, in order to kill bacteria, yeasts, 

 and molds, as all three may be present in a poorly baked loaf of bread 

 and interfere not only with the keeping quality of the bread, but also 

 with the health of the consumer. The careful housekeeper will have 

 clean dishes in which to measure her ingredients and to mix her bread. 

 She will not sweep nor cause a dust to rise in the room where she makes 

 her bread, because bacteria are in that way raised into the air and may 

 settle on her dough. She will cover the dough in order to keep out 

 dust. With all her care there will always be some bacteria present, but 

 they do not thrive in the sugar solution so well as healthy yeast plants 

 do and at the temperature used for bread-making they do not grow so 

 rapidly as do the yeast plants. They like the alcohol that the yeast 

 makes from the sugar, however, so dough is kept at summer heat only 

 long enough for the yeast to produce sufficient gas to raise the bread but 

 not long enough for bacteria to get a start. It is better not to wrap 

 cloth around hot bread just taken from the oven, because moisture and 

 warmth favor the growth of bacteria and bread that is cooled slowly may 

 not keep so well as if cooled more rapidly. 



