72 MAINE AGRICULTURAL EXPERIMENT STATION. I915. 



One should be able to produce about 50 to 55 parts by weight 

 of acetic acid from each 100 parts of sugar. To make a vinegai 

 carrying 4 per cent acetic acid requires about 8 per cent of sugar 

 in the apple juice. 

 . There are five different conditions under which apple juice 

 may contain less than the amount of sugar indicated : The fruit 

 rnay 'be unripe; the apple juice, normal at the start, may be 

 watered; the juice may 'be made by treating the pomace with 

 water, allowing to stand and pressing a second time ; the apples 

 may be badly decayed ; apples may be used which normally con- 

 tain, even when ripe, an insufficient amount of sugar. Analysis 

 of apple juice shows that certain varieties of apples such as the 

 Ben Davis and Gano may never contain, even when fully ripe, 

 sugar enough to make lawful vinegar. 



Among the conditions that are unfavorable to the necessary 

 fermentation process are: dirty and decayed fruit; unclean 

 barrels ; too low temperature ; lack of air, due to filling the barrel 

 too full or stopping the bung-hole. 



Far too often the apples used for vinegar-making are left 

 lying on the ground until they become covered with soil and 

 more or less decayed. Under such conditions, there is seriouL', 

 danger of getting into the apple juice organisms that will inter- 

 fere with the regular alcoholic and acetic fermentations, par- 

 ticularly the latter, either by lessening the amount of those 

 products or by iproducing undesirable flavors. 



Barrels or casks are frequently used for vinegar-making 

 which are not previously cleaned, no matter what their previous 

 condition or use. Undesirable organisms may be brought into 

 contact with the apple juice in this way. 



Many, if not most, farmers place their barrels of apple juice 

 a1 once in the cool temperature of a cellar, where it will usually 

 require 6 months or more to complete the alcoholic fermenta- 

 tion. The material is left at the same temperature for the acetic 

 fermentation which takes place with extreme slowness. Under 

 such conditions it may require three years or more before the 

 acetic fermentation is completed, and ordinarily the time is 

 two years or more. 



The acetic fermentation requires the presence of air, and this 

 may be excluded by filling the barrel too full or by putting the 

 bung in tight or by doing both at once. When the barrel is 



