From THE BREWER’S JOURNAL July 1917
It is probable that it is almost impossible to overestimate the importance of the air question in a finished beer. This is one of those scientific problems which ought to afford a fruitful field for the investigations of the chemist. The practical man has a great number of questions which he requires to be answered.
In the first place, why is it that air in the finished beer constitutes a danger? Is it because of the bacterial or wild-yeast infection, which accompanies such aeration, or is it owing to some degradation, or change, in the nitrogenous matter, caused by the presence of the air itself? It is obviously important that the brewer should be told as to what is the scientific truth about these two propositions, as his brewing practice will depend largely upon what is told him. If, for instance, the first is the truth, that is that the air itself does not constitute a menace, but only the fact that it carries infection along with it, then he can go ahead and purify his air supply and feel that he is taking those steps which the best modern practice would indicate.
On the other hand, if he is told that the air itself constitutes the danger, then the money spent on the purification of the air will have been largely thrown away. Considerable experience and a fairly deep practical research into the question of air contamination in beers intended for bottling, have led us to form some general conclusions at any rate. Air in bottled beers is certainly objectionable. That is to say, if careful estimates are made of the air contents of bottled beers, and those bottled beers which contain comparatively large quantities of air are compared with those samples which contain comparatively small quantities, it will be found that the presence of over 2 percent of air, in the total gas content, has a decidedly prejudicial effect on the palate. There is a certain harshness and fatness of palate, which always accompanies air infection, and which is most characteristic and can always be recognized by an investigator who is used to this sort of research.
The question as to whether this high air content affects the keeping quality is harder to answer, because the investigator is liable to be baffled by other factors, which may have a stronger bearing on the keeping qualities than the question of air content. But investigations which we have under taken in order to satisfy ourselves whether or not the keeping qualities are affected have, on the whole, satisfied us that the keeping qualities of a bottled beer are dependent, to quite a large extent, upon the amount of air which it contains .— ( London “Brewers’ Journal”)