How to Test That Yeast Is Alive

Yeast is responsbile for the haunting aroma of homemade bread.

Nothing can ruin a bread recipe quite like dead yeast. Even if the expiration date on your yeast hasn't yet passed, it could still be kaput. In order to ensure your bread bakes up light and fluffy, rather than turning into a brick, you'll need to "proof" your yeast. However, improper proofing carries its own pitfalls. A little knowledge will enable to do it right.

Things You'll Need

• Active dry yeast
• 1/4 tsp. sugar or honey
• Instant-read thermometer
• Timer

Instructions

1. Fill a small bowl with half to three-quarters of a cup of warm, not hot, water. Mix in a quarter tsp. of sugar or honey. Author Beth Hensperger states in her book "Bread" that yeast requires a small amount of sugar to react properly.

2. Place the bowl in your microwave and microwave it on high for 10 seconds. Remove the bowl from the microwave and check the water's temperature using an instant-read thermometer. "Cook's Illustrated" magazine recommends a temperature of 110 degrees F. If the water is too cool, the yeast will not react. Temperatures above 130 will kill yeast.

3. Sprinkle the yeast called for by your bread recipe over the surface of the water. You need to make sure all the yeast gets wet and none of it sits on top of other yeast; if necessary, gently swirl the bowl.

4. Set a kitchen timer for 10 minutes. After 10 minutes, the surface of the water should look like the head on a freshly-poured beer; covered in foam. If after 10 minutes your yeast has not foamed, it is dead. Start over with new yeast.

Tips & Warnings

• Despite the name, "instant-read" thermometers do not read instantly. Some take as long as 10 seconds to provide an accurate reading. Leave the thermometer in the water long enough for the temperature to stop climbing.

References

• "Bread"; Beth Hensperger; 1988
• "Cook's Illustrated"; How Yeast Works; June 2003

Resources

• Country Living : Easy Bread Recipes