Always Use Fresh Products
Most ingredients used in baked goods like baking soda, baking powder, yeast and flour have a relatively short shelf life. It is advisable to purchase them in small quantities. To check the freshness of baking powder, pour boiling water over a small quantity—if it bubbles, it is still fresh. Flour should smell fresh and feel light, not chalky; and fresh yeast dissolved in warm (110-115˚) water will bubble and foam after a few minutes.