Are these invisible germs which cause fermentation always present in the atmosphere?
By Ewart; Reynolds Green, Introduction to Vegetable Physiology; The Soluble Ferments and Fermentation; Detmer, Practical Plant Physiology, trans.
Von Liebig attacked the doctrine that fermentation was caused by micro-organisms, and enunciated his theory of mechanical decomposition.
The phenomenon is, in fact, very like that of the fermentation of palm wine and pulque, where the juices are obtained from artificial cuts.
About this time Hansen, who had long been engaged in researches on the biology of the fungi of fermentation, demonstrated that yeast free from bacteria could nevertheless occasion diseases in beer.
"The chemical act of fermentation," writes Pasteur, "is essentially a correlative phenomenon of a vital act beginning and ending with it."
I think that there is never any alcoholic fermentation without there being at the same time organization, development and multiplication of globules, or the continued consecutive life of globules already formed."
There are two distinct types of fermentation: (1) those brought about by living organisms (organized ferments), and (2) those brought about by non-living or unorganized ferments (enzymes).
He determined the percentages of carbon, hydrogen and oxygen in the sugar and in the products of fermentation, and concluded that sugar in fermenting breaks up into alcohol, carbonic acid and acetic acid.
It also yields, by the so-called mucous fermentation, a mucous, gummy mass, mixed with mannitol and lactic acid.
The process of fermentation in the preparation of wine, vinegar, beer and bread was known and practised in prehistoric times.
Flux.A common event in the exudation of turbid, frothing liquids from wounds in the bark of trees, and the odours of putrefaction and even alcoholic fermentation in these are sufficiently explained by the coexistence of albuminous and saccharine matters with fungi, yeasts and bacteria in such fluxes.
Up to this time the phenomenon of fermentation was considered strange and obscure.
Calcium citrate must be manufactured with care to avoid an excess of chalk or lime, which would precipitate constituents of the juice that cause the fermentation of the citrate and the production of calcium acetate and butyrate.
Besides orthodox Moslems there are also Shi`ite sects, as well as a number of religious communities whose doctrine is the outcome of the process of fermentation that characterized the first centuries of Islam.
As an outcome of this alchemical doctrine the process of fermentation was supposed to have a purifying and elevating effect on the bodies which had been submitted to its influence.
Johann Becher, in 1669, first found that alcohol was formed during the fermentation of solutions of sugar; he distinguished also between fermentation and putrefaction.
In 1697 Georg Stahl admitted that fermentation and putrefaction were analogous processes, but that the former was a particular case of the latter.
Thenard stated that yeast was the cause of fermentation, and held it to be of an animal nature, since it contained nitrogen and yielded ammonia on distillation, nor was it conclusively proved that the yeast cell was the originator of fermentation until the researches of C. Cagniard de la Tour, T.
He held that every fermentation consisted of molecular motion which is transmitted from a substance in a state of chemical motion - that is, of decomposition - to other substances, the elements of which are loosely held together.
In 1857 Pasteur decisively proved that fermentation was a physiological process, for he showed that the yeast which produced fermentation was no dead mass, as assumed by Liebig, but consisted of living organisms capable of growth and multiplication.
In other words "fermentation is life without air, or life without oxygen."
This theory of fermentation was materially modified in 1892 and 1894 by A.
Liebig and Pasteur were in agreement on the point that fermentation is intimately connected with the presence of yeast in the fermenting liquid, but their explanations concerning the mechanism of fermentation were quite opposed.
Traube (1858), the active cause of fermentation is due to the action of different enzymes contained in yeast and not to the yeast cell itself.
It is only necessary to bear in mind the great part played by sterilization in the laboratory, and pasteurization on the fermentation industries and in the preservation of food materials.
Fermentation now includes all changes in organic compounds brought about by ferments elaborated in the living animal or vegetable cell.
This formula substantially holds good to the present day, although a number of definite bodies other than carbon dioxide and alcohol occur in small and varying quantities, according to the conditions of the fermentation and the medium fermented.
Duclaux found that acetic acid is formed in small quantities during fermentation; aldehyde has also been detected.
Another fact of considerable technical importance is, that the various races of yeast show considerable differences in the amount and proportion of fermentation products other than ethyl alcohol and carbonic acid which they produce.
In a top fermentation - typical of English breweries - the yeast rises, in a bottom fermentation, as the phrase implies, it settles in the vessel.
Of the greatest importance is the alcoholic fermentation brought about by yeast cells (Saccharomyces cerevisiae seu vini); this follows the equation CH120 6 =2C 2 H 6 0+2CO 2, Pasteur considering 94 to 95% of the sugar to be so changed.
Glucose also undergoes fermentation into lactic acid in the presence of the lactic acid bacillus, and into butyric acid if the action of the preceding ferment be continued, or by other bacilli.