194 LACTIC ACID BACTERIA IN DISTILLING, ETC. 



acid, e.y. 1893 wines, are particularly liable to the malady. MliLLEu-TnuiiGAU 

 (I.) found such wines were always infected with a bacillus 1.2-2.0 /i long and 

 0.3 /i broad, capable of forming lactic acid, not merely from sugar alone, but 

 also from tannic acid and another (unidentified) constituent of wine. When 

 inoculated in must, this bacillus sets 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 PORTELE (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 RIETSCH (I.), conclusively proved this in many instances ; and yet, not- 

 withstanding 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 the case to the natural susceptibility of the wine to infection. 

 No known remedy exists for the lactic taint in wine, but Pasteurisation may be 

 recommended as a preventive measure. 



152. The " Turning: " of Beer. 



Although the term " turning," as applied to wine, is not yet clearly defined, 

 still, in the case of beer, only a single malady is understood by this definition, 

 viz., the undesirable appearance of lactic fermentation. PASTEUR (III.) made 

 several observations on " biere tournee," and traced the cause to certain fission 

 fungi, which he described as long rods i p. broad and of variable length, fre- 

 quently joined together in chains. For a closer investigation of these we are 

 indebted to H. VAN LAER (I.), who in 1892 obtained pure cultures of this 

 ferment, and named it Saccharobacillus pastorianus. 



The commencement of this malady in beer is evidenced by a gradual decrease 

 in the brightness of the (previously clear) liquid, which finally becomes quite 

 turbid, and gradually assumes an unpleasant smell and taste. If the sample be 

 shaken, delicate waves of a fine thread-like character appear in the liquid, 

 resembling in appearance the fine films produced at the plane of contact between 

 two liquids of unequal densities. This appearance is so remarkable that it 

 suffices of itself to characterise the malady. After a time there separates out a 

 deposit, which Pasteur reproduced in Plate II. of his above-mentioned work, 

 and which consists apart from the yeast-cells, which may be disregarded of a 

 nitrogenous precipitate thrown down by the lactic acid, and of single cells and 



