Homemade Sour Cream

You can make your own homemade sour cream. This is a process that relies on the probiotic culture in buttermilk or sour cream, so you will need those as well as heavy cream for making it yourself. Plan ahead to give the sour cream 24 hours to thicken up, develop that tart flavor, and chill.

Buttermilk and sour cream are made with the same cultures, so either could be used. You could start with light cream, half-and-half or whole milk instead of heavy cream, but the end result will be much thinner. To increase the firmness of the sour cream, a thickening agent, such as dry milk powder, is sometimes added before the inoculation of starter cultures.

Always use clean pots, jars, and utensils when making homemade sour cream. Since you are encouraging bacterial growth during the process, it's important to only have the desired, beneficial bacterial strains present. Contamination of "bad" bacteria will outcompete the desirable bacterial cultures, which can cause bad flavors or even bubbling gasses in your fermenting cream.

Many recipes online suggest using edible acids such as lemon juice or vinegar to make sour cream, but a starter culture will produce better, more reliable results. A starter culture is a small quantity of microorganisms that are added directly into food to bring about desired changes. Sour cream starter contains several varieties of Lactococcus bacteria strains. The culture is added to the cream, and the bacteria go to work producing lactic acid. The lactic acid coagulates the protein, which thickens the cream and produces sour cream's distinctly tangy flavor.

It can be tempting to go overboard with the starter culture thinking it will set the sour cream more quickly or more firmly. After all, these are beneficial bacteria, so more can only be better, right? Sadly, no. Adding excessive amounts of starter culture means those little bacteria produce more lactic acid. This can cause high acidity in your sour cream. The result is a sharp flavor (it gets too sour) or, in extreme cases, separation of the whey. If you're using cultured sour cream as a starter, you only need a couple of tablespoons per quart of cream per quart of milk.

After adding the culture, cover it to protect and leave it unrefrigerated for 12 to 24 hours. If you refrigerate your cultured cream after adding your culture, your beneficial bacteria will stop working and your sour cream won't thicken or get sour. The setting temperature is also a significant factor in developing the final flavor. Higher temperatures during setting can lead to more acidity and a more sour flavor in the finished sour cream.

The shelf life of opened commercially-made sour cream is seven to 10 days in the refrigerator. Your homemade version will probably be good for that long. Signs to look for that it should be discarded are a moldy or foul smell, mold growing on the surface, and turning yellow or other colors.

These problems occur when mold and bacteria are introduced to the sour cream other than the desired probiotic bacteria. These can come from your fingers, used spoons, or simply waft in from the air when it is uncovered. If you see these signs, don't use the remaining homemade sour cream as a starter for the next batch or you will simply multiply the problem.

1 cup heavy cream (not ultra pasterized)
1/4 cup sour cream (or buttermilk), with live cultures (2 Tbsp.?)

Gather the ingredients.

Note: To thicken homemade sour cream, add a bit of dry milk powder or heat the cream to 180ºF and hold for 30 minutes. Cool completely before adding the starter culture. If you add the sour cream or buttermilk while the cream is too hot, you will kill the precious bacteria you need in your culture.

Some recipes suggest heating the cream to 77 degrees Fahrenheit, but others suggest 86 or even 145 degrees Fahrenheit. Heating the cream denatures the proteins, which makes the sour cream thicken, so heating to a higher temperature produces a thicker sour cream. Depending on how thick you want it, determine how hot you will choose to heat it in the first step and how long you choose to keep it hot before adding your culture.

Sour cream is made using mesophilic culture. Mesophilic cultures work best between 62 and 102 degrees Fahrenheit and die quickly at temperatures above 102 degrees Fahrenheit, so it's imperative to hold your cream in that temperature range while the cultures work. If you heated the cream above 102 degrees to thicken it, you must let your cream cool back down before adding the cultures in. Between 77 and 86 degrees Fahrenheit is the most optimal temperature range.

Mix heavy cream and sour cream or buttermilk in a clean screw-top jar.

Cover it with the lid and let stand at room temperature about 24 hours until it is very thick.

Sour cream can take a full day to set, but it can also set in as little as 12 hours, which is a pretty broad range. After the first 12 hours, check your sour cream to see how firm it's getting and how sour it tastes. If it's not thick enough or sour enough, leave it longer. If your sour cream is too sour for your taste, try a shorter set time to get a sweeter flavor. The longer it sets, the more sour flavor it will acquire, so check it several times as the flavor develops.

Chill the homemade sour cream well before using and keep it refrigerated.

You may want to stir it before using. Some separation is normal and shouldn't be taken as a sign of concern.