Quick bread leavening agents include a weak base, such as baking soda (sodium bicarbonate) plus a weak acid, such as cream of tartar, lemon juice, or cultured buttermilk, to create an acid–base reaction that releases carbon dioxide. (Quick bread leavened specifically with baking soda is often called "soda bread".) Baking powder contains both an acid and a base in dry powdered form, and simply needs a liquid medium in which to react. Other alternative leavening agents are egg whites mechanically beaten to form stiff peaks, as in the case of many waffle recipes, or steam, in the case of cream puffs. Nevertheless,
Buttermilk as "cultured buttermilk", is produced from cow's milk and has a characteristically intense sour taste caused by lactic acid bacteria. This variant is made using one of two species of bacteria—either "Lactococcus lactis" or "Lactobacillus bulgaricus", which creates more tartness. A quick version of buttermilk, known as "acidified buttermilk", is used to make paneer. This version is simply cow's milk with a food-grade acid like lemon juice or vinegar added and left to sit for at least 10 minutes. That is when the milk has curdled. The tartness of buttermilk is due to acid in the milk. The increased acidity