vinegar is bottled, canned or packed in another way. U.S. Pat. No. 4,076,844 refers to a process in which vinegar of lower acidity is subjected to freezing. The ice so formed contains very little acid and is removed by centrifugation, leaving the desired higher acidity vinegar, having an acetic acid concentration of 20 percent weight by volume or more. However, this process is expensive because it requires a large investment in machinery and entails high operating costs in the form of electrical energy and man power. In view thereof according to U.S. Pat. No. 4,076,844 a two-stage fermentation process has been developed, according to which vinegar with an acetic acid concentration between 16 and 17 percent weight by volume was obtained. In this process a mixture containing alcohol, acetic acid and Acetobacter is subjected to fermentation. When in this mixture the total concentration, that is the concentration of alcohol plus the concentration of acetic acid, is between 12 and 15% and the alcohol concentration is 1-5% and the acetic acid concentration is 7-10%, a 30-100 percent solution of alcohol in water is added. During the further fermentation the acetic acid concentration increases to 13-15%, whereas the alcohol concentration is kept substantially constant by the controlled addition of alcohol. If the acetic acid concentration has reached a value of 13-15%, the addition of alcohol is stopped and 20-50% of the fermentation liquid is introduced into a second fermentation stage without interrupting the fermentation in the first stage. The acetic acid concentration of the first fermentation stage is brought back to the starting level thereof after the withdrawal of a portion of the liquid from this stage, for example by the addition of liquid containing little acetic acid (e.g. 0-2% or 1-6% respectively), a greater amount of alcohol (e.g. more than 11% or 2.5-10% respectively) and moreover nutrient for the bacteria, whereafter the fermentation is continued. In the second fermentation stage the total concentration of alcohol and acetic acid is kept substantially constant during the continued fermentation, but the acetic acid concentration increases to above 15% and the alcohol concentration decreases to substantially zero, whereby a vinegar having an acetic acid concentration of 16-17% and an alcohol content of e.g. at most 0.2% is obtained. (In the above description the concentration of alcohol is expressed in volume by volume and the concentration of acetic acid in weight by volume.)
Answered by anil kumar
at
5:11 PM on April 07, 2008