514 STATE BOARD OF AGRICULTURE. 



It may also be caused by placing tbe vinegar in insufficiently cleaned 

 new casks from which it extracts tannic substances which blacken on 

 contact with the air. Contact with iron has the same efifect. Th-e acetic 

 acid attacks the iron, and forms colorless iron salts which change to 

 dark-colored iron salts on exposure to the air. 



The tannins may be removed by treatment with gelatin (1 to II/2 oz. 

 soaked up in warm water and added to 100 gallons of vinegar). This 

 process is called fining and is merely a means of clarification, an applica- 

 tion of the same jDrinciple as that of adding egg to make coffee clear. 

 When the coagulum settles the clear vinegar may be poured off, casked 

 and stored as usual. 



In case of the iron salts, the vinegar should be well aerated in order 

 to change all of the colorless iron salts to the colored one, then followed 

 up by the fining process. The addition of a minute quantity of citric 

 acid will prevent the recurrence of the trouble. 



Animal parasites: One of the commonest and most -troublesome dis- 

 eases of vinegar is caused by a nematode worm, the "vinegar eel." These 

 are minute worm-like animals which can be seen easily with an ordinary 

 reading glass, and even with the unaided eye by holding the vinegar 

 before a bright light in a small glass. 



They may be found in the vinegar barrel at almost any stage of the 

 vinegar fermentation, sometimes even when the acidity is very high. 

 They collect most numerously around the edges of the liquid and on the 

 surface film and interfere with the acetic fermentation by destroying 

 this film and causing it to sink. When numerous they are not only 

 disgusting in themselves but their dead bodies undergo a putrid fer- 

 mentation that may completely spoil the vinegar. 



They are easily removed from the finished vinegar by filtration followed 

 by pasteurization or fining, or by the addition of potassium metabisul- 

 fite. They are hard to control in the barrel. An infected barrel or 

 cask should be emptied as soon as discovered, washed with boiling water 

 and heavily sulfured. The source from which vinegar eels first come 

 is generally river or surface water. 



Vinegar mites are tiny animals belonging to the spider family. They 

 often accumulate in moist places around the vinegar barrels and may 

 even enter them, spoiling the vinegar if they are numerous. They can 

 be destroyed easily with hot water and prevented from entering the 

 casks by painting a ring of turpentine or kerosene oil around the 

 openings. 



Vinegar flies are also often troublesome, especially in warm weather. 

 They breed around the openings of vinegar containers and wherever they 

 find vinegar exposed to the air. If numerous, the maggots they produce 

 may get into the vinegar and deteriorate its quality considerably. Cleanli- 

 ness, and avoiding the spilling of vinegar and the leaking of casks are 

 the methods of control. The openings of casks should be covered by 

 tacking a thin cloth over them. This keeps out dust and dirt with their 

 attendant micro-organisms, as well as insects. 



FRUIT VINEGARS. 



Apple or cider vinegar made from apple wine, popularly known as 

 'Tiard" cider, needs no introduction nor further discussion as this is 



