BUTTER 99 



but much of the vinegar which we purchase is artificially pre- 

 pared from wood. When fruit juices, such as juices of apples 

 and grapes, are exposed to the air for a long time, they ferment ; 

 that is to say, yeast plants from the air make their way into 

 the fruit juices and change the sugar of the fruit into alcohol. 

 The results of yeast fermentation are alcoholic drinks known 

 as cider or wine. When these alcoholic drinks are continuously 

 exposed to the air, further fermentation occurs, bacteria develop 

 in the cider and wine and change the alcohol to acetic acid. As 

 a result of the bacterial fermentation or the change of alcohol 

 to acetic acid, vinegar is formed. Masses of vinegar-producing 

 bacteria collect at the bottom of vinegar 

 bottles and barrels and are known to the 

 housewife as " mother of vinegar." 



Acetic acid may be made commercially by 

 pouring dilute alcohol into kegs full of beech 

 wood shavings over which some mother of 

 vinegar has been placed (Fig. 42). As the 

 alcohol flows over the shavings the bacteria 



act upon it and change it to acetic acid. PIG - 42. Making 

 rp, . . . . , - . . . vinegar. 



Inis is a quick method or making vinegar. 



Much of the acid used for pickling and for salads is not vinegar 

 but dilute acetic acid so colored and flavored as to give the 

 impression of real cider or wine vinegar. Burnt sugar or caramel 

 gives a good coloring to the dilute acid, and a small amount of 

 strong apple juice is sufficient to give taste to a large amount 

 of vinegar. So numerous are the attempts to replace genuine 

 material by cheap, artificial substitutes that Pure Food Laws 

 are essential to safeguard the public. 



Butter. Butter is eaten for the sake of the fat which it 

 contains. Milk fat from which butter is made is more easily 

 digested and assimilated than animal fats such as are found in 

 meats, or vegetable fats such as are found in olive or cottonseed 



CLARK INTRO. TO SC. 7 



