Does sour milk ruin a recipe?

Whether sour milk ruins a recipe depends on the recipe and the purpose of the milk in the recipe. Milk can turn sour due to bacterial fermentation, converting the lactose sugar in the milk into lactic acid. This results in a tangy or acidic taste and a thicker consistency.

In general, if a recipe relies on the rising action of baking powder or baking soda, such as in cakes, biscuits, or pancakes, sour milk can be a good substitute for fresh milk. The acidity in the sour milk reacts with baking soda or baking powder, releasing carbon dioxide gas that helps the batter or dough to rise. In these cases, sour milk can actually improve the texture and flavor of the baked goods.

However, if a recipe calls for fresh milk and does not rely on baking powder or baking soda for rising, sour milk may alter the intended flavor and texture of the dish. For example, in custards, puddings, sauces, or beverages, the sour taste can be undesirable and make the dish unappealing. Additionally, sour milk may cause dairy-based products like yogurt, cheese, or ice cream to curdle or spoil if used as a substitute for fresh milk.

Therefore, it is essential to carefully consider the role of milk in a recipe and understand its function before substituting sour milk. If uncertain, it is best to use fresh milk to ensure the intended flavor and texture of the dish.