WINE, CIDER AND VINEGAR 



185 



air. This surface is usually supplied by use of 

 shavings, blocks of wood, cobs, strips of rattan, 

 coal and the like. 



The generator must first be charged or infected 

 with the proper kind of bacteria. This is generally 

 done by pouring through it a culture of some 

 desirable species. The organisms are deposited 

 on the surfaces of the substratum employed and 

 devolpe their zooglcea masses, so that the whole 

 is covered with a layer of the slimy mother. 



In the perforated disk or false head are a large 

 number of small holes, each generally provided 

 with a piece of wicking or string, down 

 which the alcoholic solution can trickle and 

 thus be brought, in a thin layer, in con- 

 tact with the bacteria. The alcoholic solu- 

 tion IS introduced into the space above the 

 false head, either by a spout, tilting trough 

 or "sparger," a set of revolving arms per- 

 forated -with holes from which the alco- 

 holic solution is forced into the top of the 

 generator. 



Below the false bottom is a row of holes 

 through which air is admitted, and at the 

 bottom a receptacle for the liquid which has 

 passed through the generator. The oxidation 

 of the alcohol within produces heat, and there is a 

 constant updraught of air inside the generator 

 from the holes below. Thus the solution which has 

 been added is constantly coming in contact with 

 fresh organisms and fresh air and oxidation is 

 rapid. It is found practically that it requires about 

 1,000 liters of air to oxidize each 100 grams of 

 alcohol. 



Great care has to be taken with the heating as 

 well as the ventilation of a vinegar factory. 

 Since so much heat of oxidation is produced within 

 the generators where the action is taking place, it 

 is necessary to regulate the surrounding tempera- 

 ture so as not to get too high heat for the best 

 bacterial activity. As the oxidation is usually 

 not complete in a single generator, a vinegar 

 factory is generally so arranged that the solution 

 has to be pumped but once, and then flows by 

 gravity from one generator to another until all 

 the alcohol has been oxidized. 



It is manifest that any substance which can be 

 fermented to alcohol may be used as a starting 

 point in vinegar-making. Thus, sugar, starch, and 

 the like, may be used, but in such cases a prelimi- 

 nary alcoholic fermentation, by means of yeast, is 

 necessary. 



The product of the fermentation by the acetic 

 bacteria, while mainly acetic acid and water, also 

 contains acetal, aldehyde, and acetic and formic 

 ethers, all of which combine to give the typical 

 fruity refreshing odor and the characteristic taste. 



The yield based on theory. 



Knowing the alcoholic strength of the solution 

 fermented, the chemist can easily calculate what 

 the theoretical yield should be from the equation 

 given. In practice it is found that the yield is 

 about 80 to 90 per cent of the amount theoretically 

 possible, and may even fall to 70 per cent. 



The character of the organisms may be of 

 importance here in addition to the other fac- 

 tors which have been indirectly suggested above 

 (evaporation and insufficient oxidation). Some 

 forms of acetic bacteria are so powerful in their 

 oxidizing abilities that they even attack the 

 acetic acid itself, oxidizing it to carbon dioxid 

 and -water. 



Special vinegars. 



Special kinds of vinegars are sometimes pre- 

 pared, having peculiar or characteristic tastes and 



Fig. 270. Kvaporator. 

 For continuous cider- and jelly-making and the like. 



odors. These are generally due to the addition of 

 essential oils of certain plants, or maceration of 

 the plants themselves with some of the vinegar. 

 Tarragon, anise or herb vinegar may be cited as 

 belonging to this class. 



Home-making of cider vinegar. 



The following instructions for making cider 

 vinegar at home are from Bulletin No. 258 of 

 the New York Agricultural Experiment Station 

 (1904): 



"Among the conditions which may produce vine- 

 gar below standard are these: (1) The juice may 

 be poor to start with because made from varieties 

 of apples low in sugar, from green apples or from 

 overripe or decayed apples; or the juice may be 

 watered either directly or by watering the pomace 

 and pressing a second time. (2) The fermentation 

 processes may be delayed or disturbed by using 

 dirty fruit or unclean barrels, thus affording 

 entrance to undesirable organisms and causing the 

 wrong kind of fermentation; the temperature may 

 be too low to insure the necessary activity of 

 favorable organisms; or air may be excluded by 

 filling the barrel? too full or putting the bung in 

 too tight so that the bacteria can not live and 

 work. (3) The acetic acid may disappear after its 

 formation, destructive fermentation being encour- 

 aged by leaving the bung-hole of the barrel open 

 or the barrel only partially full. 



" Briefly summarized, the method to be employed 

 for the manufacture of good vinegar at home, 

 without the use of generators, is this : Use sound, 

 ripe apples, picked or picked up before they have 

 become dirty, if possible, otherwise washed. Observe 

 the ordinary precautions to secure cleanliness in 

 grinding and pressing, and discard all juice from 

 second pressings. If possible, let the juice stand 

 in some large receptacle for a few days to settle, 



