516 STATE BOARD OF AGRICULTURE. 



Pear vinegar containing 8.89 per cent acetic acid has been made 

 (Oregon Expt. Sta.) within four months from the time the fruit was 

 pressed by the use of pure cultures for controlling the successive stages 

 of vinegar fermentation. 



Prune vinegar of excellent quality has been made (also at the Oregon 

 Sta.) containing 6.89 per cent, acetic acid. The only objection to it 

 was its dark color. Undersized and otherwise unsalable prunes were 

 used for the purpose. The prunes were first washed and then run 

 through a home-made machine with spike-rollers which lacerated 

 them. The pulpy mass Avas then inoculated with a pure culture 

 of yeast which by causing a strong and rapid fermentation broke down 

 the cell walls of the prunes, thus liberating the clear juice, which flowed 

 into a receptacle below the vat. This method of securing the clear 

 liquid was inexpensive and very satisfactory. A little more than 3 gal- 

 lons of juice was secured in this way per bushel of fruit. Ten per cent 

 of alcohol was formed in ten days, then the fermented prune juice was 

 inoculated with acetic bacteria. 



Other fruit vinegars: No extensive work has been done in the U. S. 

 Government Experiment Stations on fruit vinegars other than those 

 mentioned in this bulletin, with the exception of oranges. There is good 

 reason for believing, however, that all fruits which contain sufficient 

 fermentable sugars may be made into vinegar. 



GRAIN VINEGARS. 



Malt or grain vinegars require much labor and knowledge for their 

 preparation because of the nature of the raw material. With this type 

 of vinegars the raw material is starchy instead of sugary as is the case 

 with fruits, and before it can be fermented to alcohol and later to acetic 

 acid, the starch has first to be changed into sugar by diastase, an enzyme, 

 which carries out this process during the germination of the grain, or by 

 hydrolysis using steam under pressure. 



Briefly the enzymic process preliminary to the acetic fermentation is 

 accomplished as follows : first, a portion or all of the grain, is soaked in 

 water, allowed to germinate and then dried. This resulting substance 

 is malt. During this time the diastase develops. Then the malt is 

 crushed, mixed with unmalted cereals or sugar usually, and heated with 

 water during which time the diastase changes the starches into sugar. 



This sugary solution can then be fermented successively with yeasts 

 and with acetic bacteria to produce grain vinegar. 



Malt vinegar is of a brown color and its odor is suggestive of sour 

 beer. It is used largely in Great Britain. 



Honey vinegar: Next to wine and malt vinegars in quality comes 

 that made from honey. It is quite evident that honey has to be diluted 

 to quite an extent before fermentation can take place. This dilution 

 besides reducing the percentage of sugar in solution reduces also the 



