Why does yeast make bread rise?
Show answer & explanation
Answer: Fermentation produces CO₂ gas
Air bubbles expand when baking — Wrong. Air expands when baking, but yeast creates CO₂ bubbles through fermentation before baking—that's what leavens dough.
Fermentation produces CO₂ gas ✓ — Correct! Fermentation! Yeast makes bread rise through: (1) Yeast (Saccharomyces cerevisiae)—single-celled fungus. (2) Consumes sugars in dough: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂↑. (3) Fermentation—produces ethanol + carbon dioxide gas. (4) CO₂ trapped in gluten network—dough expands. (5) Baking: alcohol evaporates, bubbles set. Living organism! Needs warmth, moisture, food. Also produces flavor compounds. Proofing time: 1-2 hours (doubling). Ancient leavening method—Egyptians!
Chemical leavening agent — Wrong. Yeast is biological leavening (fermentation). Chemical leavening: baking powder/soda (acid-base reaction), different process.