Today in 1893, US Patent 491939 A was issued, an invention of Charles A. Hansson, for his “Process of Producing Pure Cultivated Pressed Yeast.” There’s no Abstract, but the application begins by stating that he’s “invented certain new and useful Improvements in Processes of Producing Pure Cultivated, Pressed Yeast, of which the following is a specification.”
For the production of a pure cultivated pressed yeast it is necessary to have the fluid out of which the yeast is to receive its nourishment free as far as possible from foreign ferments and bacteria, that is sterilized.
According to methods heretofore used in the manufacture of yeast the sterilizing of this fluid could not have been effected to any advantage because, as the theories now existing indicate, the pepsin and not the lactic acid (the latter serving merely as a mediator) acts as a converter of the albumin into peptones, and as the pepsin contained in the grain is insufficient to transform all albuminoids in the mash into peptones, a comparatively small part of it was so transformed, and the greater part would, consequently, during the process of sterilizing, coagulate and thus be rendered insoluble, that is useless as nourishment for the yeast plant. To overcome this difliculty I make use of an additional increment of pepsin, by adding to the mash, a reinforcing quantity of pepsin and by leaving the mash under the influence thereof, together with some inorganic acid, (when necessary) and at a temperature most favorable for the pepsin, whereby much more of the albumin contained in the raw material is transformed into peptones, and I acquire a fluid which may be submitted to heating sufficiently for sterilizing with but little or no detrimental coagulation of albumin. Through the heating process I am enabled to procure a fluid sufficiently sterilized and thereby practically prepared for a pure cultivated yeast.
Having the fermenting tub covered and introducing into the fluid by mechanical means, sterilized air favorable for the development of the yeast, I avoid its infection which would take place should the fermentation be carried out in the usual way.