LACTIC ACIDIFICATION OF WINE. 



253 



The production of the two last-named acids was ascribed by 

 PASTEUR (XII.) in 1866 to the action of fission fungi. Experi- 

 ence shows that vintages poor in acid, e.g. 1893 wines, are par- 

 ticularly liable to the malady. MULLER-THURGAU (I.) found such 

 wines were always infected with a bacillus 1.2-2.0 p, long and 

 0.3 ju broad, capable of forming lactic acid, not merely from sugar 

 alone, but also from tannic acid and another (unidentified) con- 

 stituent of wine. When inoculated in must, this bacillus set up- 

 lactic fermentation. 



Musts that from any accidental cause have been deprived of 

 the whole or a great part of their acid content are therefore very 

 susceptible to this kind of infection. Thus, MACH and PORTE LE 

 (II.) report on a considerable occurrence of lactic acidity in South 

 Tyrol, where, in the autumn of 1882 and 1883, the vineyards in 

 the lowlands of Etsch were flooded, and the grapes became in- 

 crusted with the carbonates of lime and magnesia. Consequently 

 a considerable portion of the acid in the must became neutralised 

 in the process of crushing, the immediate result being complaints 

 of the appearance of lactic acidity. On the other hand, those 

 grapes that had been freed from the incrustation of carbonates, by 

 treatment with dilute sulphuric acid before crushing, escaped the 

 malady. 



Here, as also in most other maladies of wine, the true cause of 

 the evil is to be sought in the defective constitution of the liquid. 

 If the presence of disease-producing germs were the sole essential 

 factor, there would be hardly ever any good wine at all, because 

 all grapes and therefore all fresh must are infested with a 

 variety of species of fission fungi, both harmless and injurious. 

 The researches of MULLER-THURGAU (II. -IV.), MACH and PORTELE, 

 and MARTINAND and KIETSCH (I.), conclusively proved this in 

 many instances ; and yet, notwithstanding the (often considerable) 

 infection thus produced, the must under normal conditions resists 

 its foes so effectually that the matured and bottled sound wine is 

 free from bacteria. This fact, demonstrated by SCHAFFER and 

 FREUDENREICH (II.), is so decisive that it was regarded by both 

 these workers as an indication of purity, since the made wines 

 examined by them invariably exhibited a larger or smaller content 

 of bacteria. In future investigations on the subject of the diseases 

 of wine, more attention will have to be paid than has hitherto been 



