To test the strength of baking powder -
Mix 1 teaspoon baking powder with 1/3 cup hot water.
If it bubbles it's still active and it will still make your baked goods rise.
To test the strength of baking soda -
To test the rising ability of of dry yeast -
Add 1 teaspoon sugar to one cup of water. The expiration date on a packet of yeast is the date past which the activity may have diminished.
Sprinkle a small amount of dry yeast on top of the water.
If it bubbles in 5 to 10 minutes, the yeast is still fresh and active.
You can still safely use it after the expiration date, but the time required for rising will be longer.
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