Buttermilk is primarily due to lactic acid produced by lactic acid bacteria while fermenting lactose, the primary sugar in milk. As the bacteria produce lactic acid, the pH of the milk decreases and casein, the primary milk protein, precipitates, causing the curdling or clabbering of milk. This process makes buttermilk thicker than plain milk. While both traditional and cultured buttermilk contain lactic acid, traditional buttermilk tends to be less viscous, whereas cultured buttermilk is more viscous. Buttermilk can be drunk straight, and it can also be used in cooking. Soda bread is a bread in which the acid in buttermilk reacts
Old-fashioned doughnut invented, but this very likely occurred "after" the cake doughnut was invented. Prior to circa 1829, doughnuts were typically the yeast-risen variety in the U.S. Circa the 1830s, the leaveners baking soda and baking powder began to be available to U.S. consumers, which is around the same time that cake doughnut recipes first appeared in U.S. cookbooks. Primary ingredients in an old-fashioned doughnut include flour, sugar, eggs, sour cream or buttermilk, and leavening agents such as baking powder or baking soda. Additional ingredients may include milk, butter, vanilla extract and salt. The use of buttermilk or sour cream may impart