340 FERMENTATION 



absorbed, the nitrogenous body begins to putrefy, and the sugar passes into fermen- 

 tative activity. The necessity for oxygon is at tho commencement of the decomposition ; 

 when the putrefaction of the albumen or gluten has once begun, it extends throughout 

 the mass without requiring any farther action of the air. These may bo regarded as 

 natural ferments. Yeast is an artificial one. This body will bo more particularly 

 described. See YEAST. 



To produce a vinous liquid, it is necessary that there shall be present sugar, or 

 some body, as starch or gum, capable of conversion into sugar, a certain portion of 

 water, and some ferment for all practical purposes, yeast; and the temperature 

 should bo steadily maintained at about 80 Fahr. Both cane and grapo sugar yield 

 alcohol by fermentation ; but Liobig considered that cane sugar, before it undergoes 

 vinous fermentation, is converted into grapo sugar by contact with the ferment, 

 and that, consequently, it is grapo sugar alone which yields alcohol and carbonic acid. 



Grapo sugar, as dried at 212, contains exactly the elements of two atoms of alcohol 

 and four of carbonic acid ; as 2(C 4 H 6 2 ) and 4C0 2 arise from C^EW. 



Cane sugar takes an atom of water to form grape sugar. It follows therefore that 

 cane sugar should in fermenting yield more than its own weight of carbonic acid and 

 alcohol; and ic has been ascertained by experiment that 100 parts actually give 104, 

 whilst by theory 105 should bo produced, consisting of 5T3 of carbonic acid, and 637 

 of alcohol. (Kane.) Dr. Pereira has given the following very intelligible arrange- 

 ment to exhibit these changes : 



These facts will sufficiently prove that vinous or alcoholic fermentation is but a meta- 

 morphosis of sugar into alcohol and carbonic acid. 



Such are the generally-received views. "We find, however, some other views pro- 

 mulgated which it is important to notice. 



The following remarks on the Fermentation of Worts, as coming from the hands of a 

 practical brewer, are of considerable value : 



As to the theories respecting the causes of fermentation that have for some timo 

 past engaged the attention of the highest scientific talent of the present day, it would 

 be premature, and, perhaps, somewhat to be deprecated, to attempt in an article of 

 this kind to establish either the one theory or the other ; it is sufficient to the pur- 

 poses of the brewer's art to know the general principles that affect fermentation, moro 

 particularly the alcoholic fermentation of beer-wort, and a long-past experience has 

 taught us that these can be reckoned up and controlled with all the precision attainable 

 in ordinary chemical manipulations. 



The ferment, under the names of Yeast, Barm, Store, or Must, when examined under 

 a tolerably powerful microscope, in physical appearance seems to be composed of in- 

 numerable spherical forms, semi-opaque, and somewhat of a cream colour, varying 

 according to the shade imparted to the malt in the process of drying. Perhaps the 

 best way to conduct tho examination is as follows : Select a well-distended bubble 

 of yeast, just touch it with a glass plate, immediately transfer it to the microscope 

 and commence the examination, directing the light from the reflector underneath, so 

 that it shall pass upward through tho glass plate. The thin film of yeast adhering 

 to it will then be in a very convenient form for careful examination ; it will then :it 

 once bo seen that the spherules are agglomerated together with just the same accident 

 that would occur with ordinary soap-bubbles, no appearance of any regular or 

 arrangement being evinced. As the yeast dries, these individual spheres or spherules 

 burst in like manner to the soap-bubble alluded to, and the substance of which it 

 was composed falls on the spot to which it had become fixed ; it would appear to have 

 contained gas only, for neither internal structure nor evon liquid is discoverable. 

 Now take a drop of the beer-wort in a state of active fermentation, place it on the 

 glass plate support of a microscope, and hold it up to tho eye, allowing a sufficiently 

 strong light to pass through it. If tho microscope be now rolled round after the 

 manner of an ordinary kaleidoscope, the ^phrrulc.s will be seen to roll about the fluid 

 in exactly the same manner that shut wouM in tho lattor instrument ; but of murM! 

 allowance must bo made for the difference in their specific gravities respect i\ 

 tho density of the medium enveloping each. If eomo of the bottom yeast bo now 

 examined in the like manner, it will appear to havo amongst it quantit 

 spherules in a ragged condition. In addition to tho spherical forms just described, 



