Is nine year old baking powder harmful if used?

You're asking a very important question! It's crucial to understand that baking powder has a shelf life.

Here's why using expired baking powder is a concern:

* Reduced Leavening Power: The chemical reaction that makes baking powder work weakens over time. This means your baked goods won't rise properly, resulting in dense and disappointing results.

* Off-Flavors: Expired baking powder can leave a bitter or metallic taste in your baked goods.

* Potential Safety Concerns: While generally safe, expired baking powder can be less effective and cause inconsistent results, which could lead to undercooked food.

So, to answer your question directly: Nine-year-old baking powder is likely not harmful, but it will be much less effective at leavening your baked goods.

Here's what you should do:

1. Check the Expiration Date: If you have a can of baking powder, check the expiration date. If it's expired, it's best to discard it.

2. The "Float Test": You can do a simple test to check for freshness. Add a teaspoon of baking powder to a cup of hot water. If it fizzes and foams, it's still good. If it just sinks to the bottom, it's likely expired.

For the best results, use fresh baking powder, and always follow the recipe instructions.