Signs that yeast is alive and working
Confirming yeast activity avoids stalled rises and wasted ingredients. For active dry yeast or instant yeast, a simple proofing test or observation during mixing can tell you whether the yeast is viable. Fresh yeast (cake) should also be tested if its age is uncertain.
Proofing method for active dry yeast:
- Warm water: use 100–110°F (38–43°C) water—too hot will kill yeast, too cool slows it down.
- Add a pinch of sugar: this gives the yeast a quick food source to wake it up.
- Sprinkle yeast into the water and wait 5–10 minutes.
- Look for foam or a frothy layer on the surface—this indicates active fermentation.
Instant yeast differs slightly:
- Instant (rapid-rise) yeast often doesn’t require proofing and can be mixed directly with dry ingredients. If in doubt, proof a small test sample as above.
Signs of active yeast during dough making:
- Quick bubbling in preferments or starter activity within hours.
- Dough becomes puffy and shows small gas bubbles during bulk fermentation.
When yeast is likely dead:
- No foam in the proof test after 10–15 minutes.
- Dough shows minimal rise after extended time in a warm spot.
- Yeast that smells sharply off or looks discolored should be discarded.
Practical tips:
- Store yeast in a cool, dry place or refrigerate/freeze for long-term freshness.
- Use water at the right temperature; household tap can be too hot—test with a thermometer.
- If baking with long cold ferments (refrigeration), smaller quantities of yeast suffice and proofing tests aren’t necessary.
A quick foam test is inexpensive and reliable—always proof older yeast to avoid failed batches.