508 STATE BOARD (3F AGRICULTURE. 



Length of fermentation periods: The lower the temperature, the 

 greater the length of time necessary for each of the two stages of vinegar 

 fermentation. In ordinary cellar storage it takes from one to six months 

 for all the sugar to become converted into alcohol. By adding a pure 

 culture of yeast to the fresh fruit juice and keeping it at 65 degrees to 

 75 degrees Fahrenheit, the period of alcoholic fermentation can be re- 

 duced one-half or more. 



The acetic fermentation under ordinary cellar storage takes much 

 longer for completion than the alcoholic; the time required may be all 

 11) e way from a year to two or even three years. Sucli an extensive period 

 of time is wholly unnecessary! If the acetic fermentation be controlled 

 by the addition of a pure culture of vinegar bacteria and the temperature 

 is favorable, market standard vinegar may be formed in a few months. 

 Just recently several home vinegar makers have shortened the time of 

 the acetic fermentation to about three months just by paying attention 

 to these two things, inoculation with pure cultures and temperature. 

 In the "quick vinegar process," the common commercial method of 

 vinegar-making, the time for the acetic fermentation is shortened to a 

 few days instead of taking weeks and months for completion. This 

 quick process is described briefly on pages 509 and 510. 



fitorage of the finished product: When the acetic fermentation is 

 complete, that is, when all the alcohol but 1 to 2 per cent has been con- 

 verted into acetic acid, all bacterial and other fermentative action should 

 be stopped ; then it should be stored so as to prevent a decrease in acid- 

 ity. As the germs which may destroy the acid need air for their develop- 

 ment, it follows that a good method of storing the finished product is 

 to fill the barrel or cask fuU of the vinegar, bung it tightly to keep out 

 the air, and store in a cool cellar. 



Better still, "rack" or siphon off the vinegar and store in a clean, 

 freshly scalded barrel or cask, filling, bunging, and storing it as above. 

 This vinegar if drawm off carefully should be perfectly clear and of a 

 more or less amber color and will keep better than if left in contact 

 with the dregs of the old barrel which consists of enormous numbers 

 of living and dead yeast and bacterial cells. Racking off the "hard" 

 cider into a clean barrel at the close of the alcoholic fermentation will 

 eliminate these dregs to a large extent and insure a better acetic fer- 

 mentation. 



Clarification of vinegar: Vinegar as it is drawn off from the barrel 

 or cask will be nearly clear if it has been made from a clear wine. If 

 vinegar of extraordinary clarity is desired for bottling purposes, how- 

 ever, it Avill be necessary to clarify it by a special ])rocess known as 

 "fining." The principle of "fining" is the same as that of using an egg 

 to clear coffee. According to Bioletti* the best results are obtained by 

 using isinglass. One-half to tliree-fourths of an ounce is employed for 

 eacli one hundred gallons of vinegar. 



"The isinglass is cut into small pieces and soaked for twelve to twenty- 

 four hours in a little water containing acetic or tartaric acid equal in 

 weight to the isinglass used. When thoroughly soft it is then rubbed 

 several times fhrougli a fine sieve, gradually adding a litfle more water 

 until a perfectly fiuid liquid is obtained. This fluid is then well-mixed 



* Bioletti, Fredericlc I., Grape Vinesar, Bui. 227, Calif. Expt. Sta., 1912. 



