Manufacturing of Commercial Yeast

Manufacturing yeast is like farming. Manufacturing involves preparation, seeding, cultivations and harvesting. As mentioned yeast loves sugar. In commercial production molasses is provides as the sugar source. Molasses is a byproduct of refined sugar beets and sugar cane.  Quality assurance is also another important aspect of manufacturing.  Samples are checked by labs to make sure results are consistent and pure. Preparing the molasses before it is used in conjunction with yeast is the first step.  The molasses is clarified and sterilized. This prevents bacterium and other organisms to be introduced. The molasses is diluted with water, adjusted for acidity and heated. The molasses is brought to just below boiling and filtered through heavy cloths. If it is brought above a boiling temperature, the molasses will cook, harden and can even burn. After the molasses is clarified, yeast can be propagated. Seed yeast is laboratory controlled and cultivated. It is in a controlled environment so as not to allow wild yeast and cross contaminate samples. The yeast seeds are taken cared for by their strain characteristics. Some strains may need to cooled at different temperatures, or kept in the dark, depending on their biological make up. All types of cultures are transferred into small flasks so the strains grown. In the transfer process, all the vessels are sterilized and made transition is made with special care.  Once the yeast out grows its small task hundreds of flasks are moved into tanks that can hold 1,000 gallons in volume. Here a new term is used. “Stock yeast” is separated from baker’s yeast and alcohol yeast. They are stored in refrigerated tanks until further use. Once yeast is ready to be fermented, the yeast is measured in quantities of molasses and air. The temperature, and acidity is controlled and adjusted by the addition of ammonium salts. The vessels in which stock yeast is fermented can be large as to 40,000 gallons. The sterilization of this yeast should be considered. Cleaning with steam is one way to keep chemicals out. The harvesting of yeast can occur once after nutrients, gasses and sugar is added.  Harvesting yeast is done by machines called “separators.”  Separators allow concentrations of the yeast by passing through fermented liquid. The yeast cells are pumped by large pumps. In the instance of bread yeast, an off-white liquid is called “cream yeast”. This yeast is further processed/dried depending on its use.