1) Baking Soda is said to have an infinite shelf life, but after a few years we would recommend a test.
2) Baking Powder has a shelf life of about 9-12 months. Things come out of the oven flat when baking power expires.
3) Flour has expiry dates on the bags, about a year. If you store flour in a food safe container it will last years. Shelf life greatly improves when flour is kept in sealed containers.
4) Yeast is one to keep an eye on the expiry date. We always recommend our customers store it in the fridge. If kept cold it should last about 6-8 months.
Test if it’s Fresh
1) Baking Soda – Add half a teaspoon of vinegar to a cup of hot water, then stir half a teaspoon of baking soda. Bubbles prove it deserves it’s place in the cupboard.
2) Baking Powder - To check the freshness of baking powder, pour boiling water over a small quantity—if it bubbles, it's still fresh.
3) Flour – It should smell fresh and feel light, not chalky.
4) Yeast – When dissolved in warm water, it will bubble and foam after a few minutes