250 LACTIC ACID BACTERIA IN DISTILLING, ETC. 



the fermentative organisms, to sulphuretted hydrogen, which spoils 

 the odour of the alcohol. An addition of artificially prepared 

 lactic acid to the mash is too expensive, and its substitution by 

 mineral acids is, with a single exception, impracticable, owing to 

 their injurious action on the yeast. Up to the present only a 

 single reagent has proved useful, viz., hydrofluoric acid, which 

 was introduced into distillery practice by J. EFFRONT (II.). 



This so-called hydrofluoric process i.e. the use of this acid, 

 either in a free state or in the form of salts, especially as am- 

 monium fluoride has already passed through two stages of de- 

 velopment and given rise to a number of investigations and 

 treatises, which will be found epitomised in an essay by H. 

 CHATBLINEAU and A. LEBRASSEUR (I.). EFFRONT (I.) commenced 

 his publications on the subject in 1890. His initial proposition 

 was to add between 4 and 8 grams of HF per hectolitre (22 

 galls.) to the mash (treated in the usual manner) before pitch- 

 ing with the yeast, this quantity being sufficient to prevent the 

 development of injurious bacteria. 



Hydrofluoric acid surpasses all other mineral acids in its anti- 

 bacterial powers, since, according to Effront, 25 m.grms. of this 

 acid per 100 c.c. of wort will prevent the appearance of lactic 

 or butyric fermentation, whereas 200 m.grms. of hydrochloric acid 

 or 300 m.grms. of sulphuric acid are necessary to produce the same 

 results. The butyric acid bacteria, being more susceptible to the 

 influence of acids, can be repressed by as little as 10 m.grms. of 

 HF per 100 c.c. 



This original hydrofluoric acid process entailed no alteration 

 in the customary method of preparing the yeast, and in particular 

 the souring of the mash remained unchanged. Effront, how- 

 ever, endeavoured to render this preliminary treatment super- 

 fluous by modifying his method into the so-called new hydrofluoric 

 process by adding a sufficient quantity of hydrofluoric acid or 

 fluorides to the sweet mash instead of leaving it to sour spon- 

 taneously. 



Here naturally follows the question of the action of hydrofluoric 

 acid on the vital activity of yeast. It has been proved that the 

 susceptibility of the various races of yeast to the influence of this 

 acid differs, a circumstance which explains the irregular (sometimes 

 good, sometimes bad) results yielded by the old process. In dis- 

 tilleries using very susceptible yeast the prescribed addition of 

 HF to the mash might not only be without any good result, but 

 probably even give rise to unfavourable symptoms, such as sluggish 

 or imperfect fermentation. 



The discovery that cell-reproduction on the one hand and 

 fermentative activity on the other are affected in different degree 

 is an important one. According to EFFRONT (III.), the former is 

 completely arrested by the addition of 300 m.grms. of NH 4 F per 

 100 c.c,, whereas the fermentative energy is merely reduced, not 



