192 LACTIC ACID BACTERIA IN DISTILLING, ETC. 



of hydrochloric acid or 300 mgrms. 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 mgrms. 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, however, endeavoured to render this preliminary 

 treatment superfluous by modifying his method into the so-called new hydro- 

 fluoric process by adding a sufficient quantity of hydrofluoric acid or fluorides to 

 the sweet mash instead of leaving it to sour spontaneously. 



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 distilleries 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 te EFFRONT (III.), the former is completely arrested by the addition 

 of 300 mgrms. of NH 4 F per 100 c.c., whereas the fermentative energy is merely 

 reduced, not stopped, by this quantity. The same authority has also showed 

 (IV.) that yeast can be gradually accustomed to large additions of fluorine. In 

 this manner a given yeast can be brought to withstand an addition of 300 

 mgrms. of HF per 100 c.c. without losing its reproductive power. Doses below 

 this limit up to about 200 mgrms. per 100 c.c. retard reproduction, but 

 stimulate the decomposing energy of the organism, and therefore lead to a larger 

 production of alcohol. The yeast becomes so much accustomed to this stimulant 

 that it is subsequently rendered incapable of unfolding its energies except when 

 pitched in a mash also containing fluorine, the yield of alcohol being otherwise 

 far below the normal standard. 



In practice the new hydrofluoric process is, in the main, carried out as 

 follows : For the preparation of the yeast-mash 4 parts iper cent, (by volume) 

 are taken from the principal mash (previously saccharified and cooled down to 

 30 C.), and a sufficient amount of hydrofluoric acid (or fluoride) added, this 

 being followed by i volume of mother-yeast to each 4 volumes of mash taken. 

 Of course, at the commencement of the season a sufficiency of pure culture 

 yeast must be used instead. The amount of added acid is regulated by the kind 

 of yeast in use, i.e. by its susceptibility; but 10 grams (say oz.) of HF per 

 hectolitre (22 galls.) of yeast-mash will generally suffice. After the addition of 

 the mother-yeast the mash, which was pitched at 26 C., quickly warms up to 

 about 31 C., at which temperature it is maintained. In this procedure the 

 older process described in the preceding paragraph is somewhat modified : the 

 heating of the saccharified yeast-mash up to 70 C., which was there found 

 advantageous, being, in the present instance, abandoned (since the injurious 

 organisms are suppressed by the HF), as is also the separate addition of malt to 

 the mash. In addition to the properties already mentioned, hydrofluoric acid 

 is also credited with exercising a favourable influence on the diastatic action, in 

 that in presence of this acid a much smaller amount of the said enzyme suffices 

 tojhydrolise a given amount of starch in a given time. The ratio of maltose and 

 dextrin is also modified in favour of the former, as much as 96 parts of maltose 

 being sometimes obtained per 100 parts of starch, whereas in presence of HC1 (or 

 HjSOJ the highest percentage of maltose amounts to 75 (or 76) per cent., and in 

 the absence of mineral acids to 74 per cent. When the yeast-mash is matured 

 (in about twenty hours time), one-fifth is set aside to serve as mother-yeast for 



