VINEGAR 



61 



is only very slightly acid, but if allowed to stand for 

 a while it becomes sharply acid. This acetic acid 

 is the result of bacterial growth and finally turns the 

 sweet, pleasant drink into hard cider or cider vinegar. 



Fig- 37- 



The process of change is a complex one, due to 

 both chemical and bacteriological agencies. When the 



Sugar to 

 Acetic Acid 



FIG. 37. BACTERIA WHICH MAKE ACETIC ACID AND VINEGAR. 

 (After Conn.) 



wild yeasts have brought about the alcoholic fermenta- 

 tion of the sweet apple juice certain bacteria take up 

 the work and produce acetic acid in a weak solution 

 which we know as vinegar. There are different spe- 

 cies capable of producing acetic acid of different 

 strengths and under different conditions. What is 

 known as the mother-of-vinegar is a dense mass of 

 bacteria a true zooglcea form. Fig. 38. 



