THE BROWNING OF WINES. 401 



and A. BOUFFARD (I.) in 1894 had denied, the probability of 

 bacterial activity in this phenomenon, it was shown by G. 

 GOUIRAND (I.) that we have here to do with the action of an 

 enzyme which plays the part of a carrier of oxygen. He isolated 

 the same (though not in a pure state) from browned (white and 

 red) wines, and produced therewith the same malady in previously 

 sterilised sound wines. This enzyme must probably be regarded 

 as acting by the absorption of atmospheric oxygen, which it then 

 gives up again, not only to the colouring matter in the wine, but 

 also to the tannin, and thus converting them into insoluble dark- 

 coloured compounds. It is to be hoped that, ere long, this matter 

 will have been made clear by further investigation. 



It is found by experience that the wines obtained in wet 

 autumns from rotten grapes, as also those affected with " sweet- 

 rot " (Edelfdule ; pourriture noble), and such as are poor in acid, 

 are subject to this malady with comparative frequency. Nessler 

 made searching investigations into the means of combating this 

 complaint in practical viticulture. The most important result 

 obtained was the discovery that the browning of wine can be pre- 

 vented by thoroughly fumigating the casks with 1-2 grams of 

 sulphur per hectolitre 22 galls, or 3.53 cubic feet of cask-room 

 before use, the malady being found, in Nessler's experiments, not 

 to ensue when the wine contained a minimum quantity of 0.003 

 per mil. of S0 2 . According to the researches of Gouirand, this 

 enzyme is destroyed by a temperature of 80 C., 60 C. being 

 apparently insufficiently reliable for this purpose. MULLER- 

 THURGAU (VI.) made the discovery, important in cellar manage- 

 ment, that the tendency of wine to turn brown could be prevented 

 by Pasteurisation, i.e. keeping it for some time at a temperature 

 of 6o-62 C., which it will endure without acquiring the so-called 

 "boiled" taste. 



The acquisition of a more accurate characterisation of the 

 enzyme, and the consequent possibility of distinguishing it from 

 other oxydases, is desirable, this being a necessary preliminary to 

 the elucidation of its origin. Possibly the enzyme is not formed 

 anterior to fermentation, but, on the other hand, its presence in 

 the grapes themselves and in the must is not absolutely precluded, 

 V. MARTINAND (I.) has actually found oxidising enzymes in wine- 

 must on many occasions. The elucidation of the conditions under 

 which browning may be caused in wines is a subject requiring 

 further investigation, the question whether the presence of special 

 metabolic products is essential, or whether the oxydase here con- 

 cerned differs from those observed by Martinand, being still un- 

 solved. Moreover, it appears from the discoveries of this observer 

 that, in the maturing of wine, the alterations of flavour occurring 

 and which may be accelerated by the influence of oxidising 

 agents (ozone, the electric current) are, under natural conditions, 

 brought about by the agency of oxydases which still require closer 

 identification. The same applies to the darkening of the colour 



VOL. I. 20 



