254 ®^ FERMEifTATIOW. 



Fermenta- Fermetitatton still appears to me however one of the most 



tion still mysterious of chemical processes; jarticularly because it 



operates only gradually, and we cannot conceive why, when 



the ferment and the sugar are intimately mixed together, 



they do not act on one another with greater rapidity. We 



might be tempted to believe, that it is partly owing to a 



galvanic process, and that it has some analogy to the mutual 



precipitation of metals. 



Theory of Mr. Be this as it may, it seems to me, that we may clearly 



Appert's mode ^Qjjggjyg jjQ,^, animal and vegetable substances are preserved 



oi preserving 



animal and by the process of Mr. Appert. These substances, by their 



vegetable contact with air, readily acquire a disposition to putrefy or 

 substances. . . . 



ferment : but on exposing them to the heat of boiling water 



in vessels well closed, the oxigen absorbed produces a new 

 combination, which is. no longer capable of exciting fermen- 

 tation or putrefaction, or which is rendered concrete by 

 heat, in the same manner as albumen*. In fact it is ob- 

 served, that a juice disposed to ferment, and perfectly clear, 

 becomes turbid at the heat of boiling water, and then is no 

 longer susceptible of fermentation, unless it be placed in 

 contact with oxigen gas. In this case, if it be made to boil 

 as soon as fermentation begins to take place, the fermenta- 

 tion is quickly stopped, and a deposition, of an animal 

 Heat destroys nature, takes place. It may farther be observed, that beer 

 the lermenting ^,gj^g^^ which has been exposed to the heat of boiling water, 

 yeistl likewise loses the property of exciting the fermentation of 



sugar. Now since must of grapes that has been boiled still 

 retains ferment in solution, which, to produce fermentation, 

 requires only the contact of air; we must conclude, that 

 only the part which has absorbed oxigen, and which is pro- 

 bably in the same state as beer yeast, is capable of coagu- 

 lating by heat. 



This is the idea I have formed of the preservation of ani- 

 mal and vegetable substances : and if, as the experiments I 

 have related seem to prove, oxigen be necessary to the 

 developement of fermentation and putrefaction, it is evi- 

 Requisites to dent, not only that the heat must be continued long enough 



♦ SegHin has supposed albumen to be the true principle of fermenta- 

 tion. See Journ. vol. XV, pp. 332, 833. C 



to 



