How to Create Sour Milk When You Don't Have Buttermilk on Hand

Two Methods for Making Sour Milk

You can make sour milk at home in two ways: through acidification or fermentation.

Acidification is the simplest and most cost-effective method, requiring just regular milk, an acidic ingredient like vinegar or lemon juice, and a bit of patience.

Fermenting sour milk takes longer and is more complex, as it needs a starter culture and several hours of incubation in a warm, controlled setting.

Buttermilk is the most popular type of cultured sour milk, produced through fermentation. You can buy ready-to-use buttermilk starter cultures or make your own by adding a small amount of store-bought buttermilk to fresh milk.

If you're looking to quickly make sour milk as a buttermilk substitute, acidification is the fastest and easiest method.

How to Create Sour Milk

Ingredients
1 cup of milk
1 tablespoon of white vinegar or freshly squeezed lemon juice

1. In a small jar or bowl, combine milk with vinegar or lemon juice. Stir the mixture and let it sit for about 15 minutes, or a bit longer, until it thickens or curdles.
   
2. Once the sour milk has reached the desired texture, use it immediately, or cover and refrigerate. It should be used within a few days. Be sure to stir or shake before using.

Yields 1 cup

Helpful Hints

• You can make sour milk with fat-free, reduced-fat, or whole milk.
• Use lemon juice or white distilled vinegar with 5% acidity, which has a neutral in taste and is colorless. In a pinch, you can use white wine vinegar. Any other vinegar is not suitable because it will give off its taste and color to the sour milk.
• The lemon juice can be freshly squeezed or bottled. When using fresh, strain it to remove pulp and seeds.
• Some recipes for sour milk list cream of tartar as an acidifier. While it does the job as a leavening agent, cream of tartar does not have the typical tanginess that you want from sour milk.
• It is best to start with milk at room temperature. If the milk is straight from the fridge, it will need extra time. The amount of time depends on the ambient temperature, and the milk will thicken and curdle further if you give it more time. But it is not a good idea to let the milk sit on the counter for hours on end or overnight to sour, like it was done in the old days. The milk may go from sour to spoiled.
• The acidification of the milk prevents the growth of harmful bacteria. But even if you turn milk into sour milk, the sell-by date on the bottle is still an indicator of when to use it. As a rule of thumb, any soured milk product should be consumed within one week after the sell-by date.