Sour cream is a cultured dairy product. This means that it is cream that has been treated with microorganisms to turn it sour. This thickens the cream and gives it a new flavor profile.
This was originally discovered before the invention of refrigerators as storage at room temperature would have caused the milk to sour and go off. The microorganisms in milk naturally include bacteria and yeast which can cause mould growth.
This has obviously been refined with the advances of technology, but the basic principle is the same. A bacteria known as diacetyl grows and turns the pH of the milk more acidic. This changes the flavour.
The bacteria in the milk feed on the lactose (the milk sugars) and produce lactic acid. The lower pH causes the casein proteins in the milk to change shape (denature) and coagulate. This is what makes the milk thicken and turn to cream. The acidity also causes starches in the flour to gelatinize during baking.
The high fat content of the sour cream adds moisture to the cake and coats the gluten proteins. This reduces the amount of gluten networks that form during baking, making the cake less doughy and more light in texture.
Milk has a relatively neutral pH and contains around 9g fat per cup. Sour cream has an acidity content of rouhgly 0.8%, but a whopping 40g fat per cup. This is one of the highest fat contents of all dairy products.
So why would you use sour cream in cakes?
As mentioned above, sour cream is very acidic in taste.
This means that using it in your cake will help to cut through some of the sweetness.
When the proteins in the milk denature and turn it to sour cream, the mixture will thicken. One main reason that bakers opt to use sour cream in cakes is that it changes the texture of the cake batter.
Sour cream has a natural consistency similar to the ideal cake batter consistency. If your cake is lacking moisture, but you don’t want to alter the texture, sour cream is the perfect solution.
The golden-brown colour indicating cakes are perfectly baked is not always easy to achieve. This browning is caused by proteins and sugars interacting with the heat. More sugars mean the browning will occur faster, and sour cream has more lactose (milk sugar) than butter.
This means that if you substitute sour cream for butter, your cake will be likely to brown faster in the oven.
Activating Baking Soda
Baking soda is used as a leavening agent in cakes, meaning that it helps them to rise in the oven. This process is caused by the release of gases in the presence of heat.
Baking soda needs to be activated by acid, therefore sour cream works well. This is not a common reason people use sour cream, but is an added benefit.
Sour cream has a high fat content, which will make your cake taste more rich and indulgent. The sour notes also complement flavours such as vanilla and chocolate well.
The slight tang in the sour cream enhances the sweet notes in the cake, making it taste out of this world!
It is hard to find suitable substitutes for sour cream due to its balance of richness and acidity.
Buttermilk mixed with lemon juice will give you an equivalent acidity level, but this will not have the same high fat content. The closest overall substitute is a thick yogurt, such as a Greek-style product.
Sour cream contains less of the casein protein than yogurt, and these work to make the cake light and fluffy. If you substitute Greek yogurt for sour cream, you will end up with a fluffier textured cake.
Frequently Asked Questions
What does sour cream replace in a cake?
Sour cream can be used to replace the oil, butter or milk in a cake, but can also be added alongside these ingredients for a richer result. It can also be used as a substitute for yogurt, cream and buttermilk.
As sour cream has a higher fat content than most of these options, you can choose to use a light or fat-free sour cream. This will give you a slightly different flavor and texture, but will work in a pinch.
Does a cake with sour cream need refrigeration?
As it is cooked, there is no danger in leaving the cake out on the work surface. Cover with aluminum foil, plastic wrap or place in a cake container. It will last 3-4 days on the worktop.
If you want the cake to last a little longer, place it in the refrigerator and it should last for up to 1 week.
Sour cream cakes are suitable for home freezing, provided it is covered tightly with aluminum foil to prevent freezer burn. Unfrosted sour cream cakes will last for 6 months in the freezer, and frosted cakes will last 2 months. To thaw, leave it on the work surface overnight.
If there is sour cream used in the cake frosting, place it in a cake container and store in the refrigerator until it is time to serve. Return to the fridge when not being eaten to extend the shelf life. These cakes should last 3-4 days if they are stored correctly.
Can I use mayo instead of sour cream?
If you do not have sour cream on hand, there is a simple way to make your own substitute.
Measure out equal volumes of heavy cream, mayonnaise and plain yogurt into a blender. Blend until well combined, or whisk in a large bowl if you do not have a blender. The consistency should be creamy and light and evocative of sour cream.
This can be used in a 1:1 ratio as a sour cream substitute. Store in a lidded jar in the fridge for up to 3 days.