252 LACTIC ACID BACTERIA IN DISTILLING, ETC. 



hydrofluoric acid for this purpose, the distiller will naturally avoid 

 employing more than is absolutely necessary. 



Although hydrofluoric acid undoubtedly affords a reliable means 

 for combating bacteria, and can be used with advantage to keep 

 yeast free from these objectionable organisms, the case is different 

 when the purification of a yeast from contaminating wild yeasts is 

 in question. EFFRONT (V.) prescribed a method which he thought 

 could effect this latter purpose, but the same was shown by A. 

 JORGENSEN and J. CH. HOLM to be unreliable. Some further 

 particulars on this point will be given in a suitable place in the 

 second volume. At present we will merely state that the hydro- 

 fluoric acid process in nowise supersedes the employment of pure 

 culture yeast; on the contrary, the value of such yeast has here 

 been revealed in a new light. 



151. The Lactic Acidification ("Ziekendwerden") 

 of Wine. 



The souring of wine and beer is by no means a uniform phe- 

 nomenon, but may, on the contrary, appear in many forms. The 

 most frequent is the vinegar taint, i.e. a partial conversion of the 

 alcohol into acetic acid by acetic acid bacteria. Fuller particulars 

 of this evil will be given in Chapter xxxvii. The subject of the 

 present paragraph is the lactic acid taint, i.e. the production of 

 acidity by lactic acid bacteria, and which is generally known in 

 Germany as " Zicke?id'iverden." This is a not infrequent malady, 

 and usually makes its appearance in company with other injurious 

 changes. Even Pasteur classed it along with the so-called turning 

 or breaking of wine, and the expression "Yin tourne" is still 

 applied in France to both phenomena, other terms being "Vin 

 monte " and "Yin qui a la pousse." The course and characteristics 

 of the malady are as follow : It mostly attacks young vintages, 

 occasionally appearing even in the first year. The wine turns 

 turbid, and the odour and flavour gradually become irritating like 

 rancid butter. The turbidity increases by degrees to such an 

 extent that the wine has the appearance of diluted milk, this 

 white break passing over finally, in many instances, into the 

 stage of black break, the wine then being in the condition of a 

 brown to inky black liquid. Concurrently with this change of 

 colour occurs a gradually increasing precipitation of dark slimy 

 masses a phenomenon characteristic of this malady. The pre- 

 sence of lactic acid in "Yins tourneV' was detected by A. 

 BALLARD (I.) in 1861. J. BERSCH (I.) examined four samples of 

 broken ("zickender") wine for their acid content, and obtained 

 the subjoined results : 



