44 MICROBIOLOGY OF SPECIAL INDUSTRIES. 



develop most commonly during the secondary fermentation or in the 

 bottle. Some may produce a disagreeable bitterness (S. pasteurianus I) 

 or other unpleasant flavor (S. fcetidus) ; many produce a persistent cloudi- 

 ness (S. ellipsoideus, S. apiculatus, S. exiguus, S. anomalus.} They are to 

 be combated by preventing contamination, by proper attenuation and 

 by pasteurizing. 



Bacterial diseases were more common before effective methods of 

 purifying yeasts were known. 



Many forms of lactic bacteria may affect the beer, rendering it acid 

 and cloudy. They occur principally where the temperature is allowed 

 to become too high and where proper care in the cleaning and sterilization 

 of utensils is not exercised. 



Acetic bacteria may occur under the same conditions and give a taste 

 of vinegar to the beer. They are more common in top fermented beers. 



Various forms of Sarcina may cause persistent cloudiness, acid, un- 

 pleasant flavors or both. This contamination may be from the air or 

 water and is relatively common. The source of infection is to be looked 

 for in the air or water. Their growth is most rapid at 16 to 20 and is 

 retarded by the antiseptic properties of hops. 



Several kinds of bacteria, bacilli, cocci and sarcinas may cause the 

 beer to become slimy or viscid and injure the flavor. This trouble is 

 particularly common, in spontaneously fermented beer. 



Wort and beer, being organic solutions containing very little acidity, 

 are favorable media for the growth of bacteria, many forms of which 

 may cause trouble. With modern methods of using pure yeast, cleanli- 

 ness and the pasteurization of bottle beer, diseases can be controlled. 



MISCELLANEOUS ALCOHOLIC BEVERAGES. 

 CIDER AND PERRY. 



These beverages are made by the alcoholic fermentation of the juices 

 of apples and pears respectively and come next to wine and beer in the 

 quantities produced. 



The composition of the fruit varies very much according to the variety, 

 especially in the matters of acidity, tannin and pectic substances. The 

 following analysis is that of a good cider apple: 



Sugar 167 . o g. per liter. 



Tannin 2 . 4 g. per liter. 



Acidity (as sulphuric) : . i . 6 g. per liter. 



