ACETIC FERMENTATION 215 



though vinegar of good quality may be secured from beer- 

 wort or malt extract. Much vinegar, however, is manu- 

 factured by the alcoholic fermentation of molasses or cheap 

 syrups. In some cases a mixture of acetic acid secured 

 from the destructive distillation of wood diluted with water 

 and colored with caramel is sold as vinegar. This is gen- 

 erally prohibited by law as fraudulent. 



One of the chief aims in commercial manufacture of vine- 

 gar is the quickening of the process. One of the earlier 

 methods, and one still practiced, is the so-called Orleans 

 method, resembling in many respects the method of vinegar 

 manufacture already described as suitable for the home and 

 farm. A cask is partly filled with a mixture of wine and 

 good vinegar. It is allowed ''to stand until a satisfactory 

 scum or membrane has formed over the surface and until 

 the' entire contents have been converted into vinegar. A 

 definite amount of the vinegar, usually a gallon or more, is 

 withdrawn and an equal amount of wine added, care being 

 taken not to break the membrane covering the surface of the 

 liquid. After the process is well started a portion of the 

 contents of the barrel may be withdrawn daily or at other 

 suitable intervals and equal amounts of wine added. The 

 method has certain disadvantages. The membrane is apt to 

 be broken and portions will settle to the bottom where the 

 organisms composing it cease growing and decompose, add- 

 ing to sediment and producing undesirable flavors. 



Pasteur and his collaborators developed a so-called vat 

 method of vinegar manufacture in which a suitable mixture 

 of wine and good vinegar was poured into a relatively 

 shallow vat and a light wooden lattice floated upon the sur- 

 face. The membrane, consisting of acetic bacteria, soon 

 developed and remained supported by the wooden frame. 

 As soon as the material had been converted into vinegar a 

 portion was withdrawn and an equal amount of unfer- 

 mented material added. This withdrawal can be made 



