Not available. Yeast powder is a common compound additive, often used in making pasta and cakes. Expired yeast powder cannot be used because expired yeast powder cannot react with baking soda to produce enough carbon dioxide. If you use expired yeast powder, The dough will not ferment sufficiently, and the final baked goods may be flat, hard, or taste bad. Moreover, expired yeast powder may become moldy or produce harmful substances. When ingested into the human body, it may cause irritation to the gastrointestinal mucosa. In severe cases, food poisoning may occur, which is detrimental to human health. Therefore, Yeast powder cannot be used after it has expired.