Yeast

Appears in
top 1000The Boston Cooking-School Cook Book
The Boston Cooking-School Cook Book

By Fannie Merritt Farmer

Published 1896

  • About
Yeast is a microscopic plant of fungous growth, and is the lowest form of vegetable life. It consists of spores, or germs, found floating in air, and belongs to a family of which there are many species. These spores grow by budding and division, and multiply very rapidly under favorable conditions, and produce fermentation.

Fermentation is the process by which, under influence of air, warmth, moisture, and some ferment, sugar (or dextrose, starch converted into sugar) is changed into alcohol (C2H5HO) and carbon-dioxide (CO2). The product of all fermentation is the same. Three kinds are considered, — alcoholic, acetic, and lactic. Where bread dough is allowed to ferment by addition of yeast, the fermentation is alcoholic; where alcoholic fermentation continues too long, acetic fermentation sets in, which is a continuation of alcoholic. Lactic fermentation is fermentation which takes place when milk sours.