What is yeast?
Yeast is a living microscopic organism which alters sugar or starch into alcohol and carbon dioxide. It is a single-celled organism that reproduces asexually and has been used in baking and brewing for thousands of years. There are at least 1,500 species of yeast, all of which are technically living organisms. Yeast occurs naturally in the environment and is in the same biological family as fungi such as mushrooms.
Yeast is commonly used in bread, alcoholic drinks, non-alcoholic drinks (soft drinks) and other things. Baker's yeast is what we use most often for leavening when cooking. The yeast reacts with oxygen and helps leaven bread, or make it rise. Baker's yeast is either active dry yeast or compressed fresh yeast. Brewer's yeast is a non-leavening yeast used in brewing beer and can be eaten as a food supplement for its healthful properties. Different kinds of yeast are used to make ale, lager, spirits and wine. It makes alcohol by reacting with the sugars that naturally occur in these drinks.
Brewer's yeast has a bitter flavor. Nutritional yeast is similar to brewer's yeast, but not as bitter because it is grown on molasses. In non-alcoholic drinks such as root beers and other soft drinks, the yeast is used to add flavor, but the process is stopped before the drink becomes alcoholic. This means the drinks are much sweeter than their alcoholic counterparts and contain more carbon dioxide. They also normally have very low alcohol content, although this is usually around 0.1 percent.