Chapter 1 : The Cause of Fermentation: Work by Chemists and Biologists, 1789 to 1850

Abstract:

This chapter describes (i) the first major chemical analyses of ethanolic (wine) fermentation, (ii) the conclusive demonstration in the early 19th century that yeasts are microbes and cause the fermentation of beer and wine, and (iii) a remarkable attack on these microbiological findings by some of the most influential scientists of the time. Indeed, the first scientific research on yeast was done not by biologists but almost exclusively by chemists, who were investigating alcoholic fermentation. One of these—the great French chemist Antoine Lavoisier— described the phenomenon of alcoholic fermentation as "one of the most extraordinary in chemistry." In order to investigate, during fermentation, the conversion of sugar into carbon dioxide and alcohol, Lavoisier carried out a number of analyses, estimating the proportions of the chemical elements in sugar, water, and yeast paste. Schwann held that yeast cells caused fermentation, because fermentation was constantly associated with yeast propagation and failed when the yeast was destroyed by heat. He also commented that the yeast itself also increased in quantity during fermentation as Jean Jacques Colin had already observed and that this kind of phenomenon was displayed only by living organisms. In 1839, Jöns Jacob Berzelius stated that evidence from microscopy was of no value and that yeast was no more an organism than was precipitate of alumina; he also claimed that fermentation occurred by means of catalysis.