STUDIES ON" FERMENTATION. 353 



S^ II. — Method of Estimating the Oxygen held in Solution 



IN "Wort. 



The use of carbonic acid gas and the cooling of the wort, 

 in contact with that gas or in contact with very limited quan- 

 tities of pure air, are by no means necessary to the application 

 of the new process. There is only one thing that is absolutely 

 essential — which is, the purity of the gases in the presence 

 of which the wort is cooled and treated. If, therefore, it is 

 well to aerate our wort, either before or during fermentation, 

 this may be done, on the sole condition that the air employed 

 does not introduce any germs of disease that are likely to 

 develop in the beer during fermentation or afterwards. The 

 question of aerating the wort is not, however, so simple a 

 matter as it seems at first sight. A very simple observation 

 will show that wort cannot be safely oxygenated by exposure, 

 without precaution, to the air, even leaving out of account 

 the germs of disease which that air may contain. It is easy 

 to show that finished wort has a decided flavour and aroma 

 of hops, as well as a sweet taste, and that it leaves a certain 

 pleasant, bitter after-taste on the palate. When we taste it 

 in this condition we cannot help thinking that a liquor 

 of the kind, after fermentation, ought to constitute a very 

 valuable beverage, as wholesome as it is pleasant. Now all 

 this pleasant and refreshing sensation that the wort leaves on 

 the palate, which is due as much to the aroma as to the bitter- 

 ness of the hop, disappears absolutely, we may say, if the wort 

 is left exposed to contact with air for a sufiicient time, and that 

 whether the air be warm or cold. We may easily perform the 

 experiment in one of our two-necked flasks, in which we can 

 preserve the wort, in contact with pure air, without any fear of 

 change. The oxygen of the air enters into combination with 

 the substances that the hop introduces into the wort, and the 

 wort, in conseqiience of this oxidation, gradually becomes 

 transformed into a saccharine decoction, without odour, in which 

 even the bitter flavour is destroyed or hidden. In other words, 

 the wort grows weak and flat, in just the same way that beer 



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