Deactivated yeast is any yeast that is no longer living and cannot produce the effects of a living, or active, yeast because of its relaxing properties. Many recipes call for some form of deactivated yeast, or dead yeast, often as a flavoring. Some people also use dead yeast such as nutritional yeast and brewer’s yeast — both of which are derived from the same one-celled fungus, Saccharomyces cerevisiae — as nutritional supplements.
Because of the relaxing properties dead yeast cells provide, deactivated yeast is often used as a reducing agent to make it easier to shape certain foods such as pizza dough and pan bread. Many other foods call for dead yeast, too. For example, one type of yeast, nutritional yeast, acts as a nutritional supplement and provides a source of protein and B-complex vitamins. Nutritional yeast is popular among vegetarians and vegans; its cheese-like flavor means it can be used for sauces, cheese substitutes, casseroles, soups, and stews, and as toppings for eggs, popcorn, pasta dishes, and salads.
Other kinds of dead yeast are favored for having nutritional value. For example, deactivated brewer’s yeast is used mostly as a nutritional supplement. Like nutritional yeast, deactivated brewer’s yeast is a source of protein and B-complex vitamins, as well as selenium and chromium.
Brewer’s yeast can be used with many of the same foods as nutritional yeast. Some studies even suggest brewer’s yeast can help people treat diabetes and high cholesterol, and may aid in weight loss. Keep in mind that deactivated brewer’s yeast should not be confused with beer yeast. Brewer’s yeast is typically a by-product of making beer, not the beer-making yeast itself, and is deactivated through pasteurization.
Many kinds of deactivated yeast are available in grocery stores, health food and wellness stores, and similar retail locations. Depending on the exact type, this type of yeast is often available in the form of power, tablets, liquid, and flakes. It is important in trying to achieve the best results to thoroughly read and follow the instructions for any recipe that calls for a type of dead yeast. It's also a good idea to read the packaging label for information on proper storage and, if using the yeast as a nutritional supplement, dosage. Although using this type of yeast in cooking is a simple process, any use of deactivated yeast as a nutritional supplement or for any other health purpose should be discussed with a doctor.