Page:Popular Science Monthly Volume 82.djvu/49

Rh are minute fungi invisible to the naked eye which attack the sugar of the bread and transform it into carbonic-acid gas and alcohol. The course of this fermentation is controlled by the presence of lactic bacteria which prevent the growth of putrefactive organisms. But here again there are lactic bacteria and lactic bacteria, yeasts and yeasts. These yeasts are again populations, mixtures of different races from which the microbiologist can select pure lines. Here Vilmorin's method must be used, i. e., filiation from a single isolated germ. Thanks to this process, Hansen and others have selected a large number of strains of yeasts, each with its particular character. For science of to-day beer yeast no longer exists, but in its place there are many distinct and constant species just as there are many distinct and constant species of lactic bacteria. The problem of the future will be, then, to regulate bread fermentation by means of these selected microorganisms.

But certain flours do not rise well. Suitable ferments must be found for them. Others, like maize flour, do not rise at all. It is therefore impossible to make bread from maize alone. In 1900, at the time of the World's Exposition at Paris, I was asked this question: "How can we find a ferment to raise dough made from maize?" No yeast tried up to that time had been able to accomplish this. I then thought of using ferment from India which I had procured through Colonel Prain, director of the Kew Botanic Garden. In applying these selection methods the late Mr. A. Netchich and I obtained from these ferments, which are employed in Sikkim and the Khasia Mountains for the alcoholic fermentation of rice and Eleusine, a leaven, which alone or associated with other yeast causes maize dough to rise and thus allows bread to be made from it. We dedicated this species to Dr. Prain (Amylomyces Prainii = Mucor Prainii). I take this opportunity of announcing this discovery and putting it in reach of all those who wish to profit by it.