Why & how sour cream is used in cakes – Sour cream science

We’ve discussed why you would use zucchini or carrots (even purple ones!) in a cake as well as how you can use corn starch powder instead of eggs. Of course there’s plenty more interesting variations to make, what about using sour cream for instance?

We recently made a new recipe from Sweet, Ottolenghi’s sweet cookbook that also called for using sour cream in the cake batter, it even required us to mix the baking soda with the sour cream (and yogurt) on forehand. As always with recipes from Sweet, it turned out fabulous again (Sweet is probably the favorite sweet cookbook by far here) with surprising flavour combinations. But it was especially that mixing of sour cream and yogurt with baking soda that got our brains working.

What is sour cream?

Sour cream truly is what the name says it is: a sour cream. In other words, cream that has become acidic, thus the pH-value has dropped.

Back in the day, when people made their own butter and other dairy products at home they would leave fresh milk to sit overnight for the cream to float to the top. (Cream has a lighter density so rises up, the opposite of sedimentation, but same physics.) Since the milk would be stored at room temperature, micro organisms would start growing in it. These micro organisms would produce various flavour components, which would slightly change the flavour of the dairy products made with it. Sour cream, but also creme fraiche for instance, originate from this natural process.

Making sour cream – Role of bacteria

Nowadays though, manufacturers precisely control what happens and when it happen. Instead of letting micro organisms grow spontaneously, manufacturers add them on purpose and within tight control. Sour cream follows the same first few steps as regular cream. Manufacturers pasteurize the cream and homogenize it, which makes all fat particles smaller and of the same size.

The cream is then cooled back down to around room temperature. At this point micro organisms will be added. These are mostly bacteria, generally species of Leuconostoc and Lactococcus. The bacteria are then left to grow in the cream for 12-18 hours. During this time the micro organisms will produce acids (lactic acid) and this is what causes the cream to turn sour. At the end of this process, the pH of the sour cream will be around 4,5.

There also exists such a thing as acidified sour cream. It’s also sour, however, in this case no bacteria were added. Instead, an acid is added during manufacturing which makes the cream sour. It does result in a different flavour profile and texture.

Sour cream characteristics

The growth of bacteria is what gives sour cream its specific properties. For instance, the bacteria will produce several components that will give sour cream its characteristic taste. One of the main components here is diacetyl. Diacetyl is a molecule that by itself will help in making something taste buttery.

Then there’s the consistency. Sour cream clearly is a lot thicker than regular cream. One of the ways it has become thicker is due to the lower pH-value. The cream has become more acidic and this causes proteins (caseins) to thicken the cream, it is somewhat similar to what happens when making paneer cheese. Also, in some cases some rennet is added. Rennet can also be added when making cheese and also helps to thicken the sour cream.

Sour cream contains quite a lot of fat, which also helps in thickening. However, you may have seen non-fat sour cream in stores. In these sour creams you will see that other ingredients have been added for thickening (e.g. starches) or it will be pretty runny and liquid.

slice of hazelnut crumble bundt cake with sour cream
A delicious soft, fluffy cake, using sour cream as part of the batter.

Why sour cream is used in cakes

There are actually a lot of reasons sour cream may be used in cakes! We’ll tick of the most important reasons. Understanding all these nuances and differences between ingredients is what will make you a better cook/chef in the long term and help you to develop new delicious recipes!

Thickness

The first, most commonly mentioned reasons for using sour cream is its thickness. If you’re baking a cake you are looking for a certain consistency of your batter. If it’s too runny it most likely won’t hold on to itself. However, if it’s too firm it won’t rise as well because it won’t be flexible enough.

Since sour cream itself has a consistency which is not too fat off from that of a cake batter, it can be added quite easily without really affecting the consistency that much! This can be very beneficial if you’d like to add some more moisture to your batter, but already have quite a liquid batter.

Sour cream vs (Greek) yogurt

If you’re using sour cream to add some extra moisture, while keep the consistency the same a good alternative would be yogurt. It’s also somewhat thicker, but contains a lot of moisture as well. However, there’s an interesting difference here. Apparently, sour cream contains less casein proteins than yogurt. Casein can improve the fluffiness of a cake, so using sour cream will make a less fluffy cake than using Greek yogurt (source, but we haven’t found any other source stating this as well, if you have another source, let us know!).

Browning of your cake & sour cream

When making a cake your recipe has to be sufficiently balanced so that it bakes on the inside, without burning on the outside. Of course temperature plays a big role here, but so does the composition of your cake batter. The main players in browning of your cake are proteins and sugars. More proteins and sugars will speed up the reaction.

Let’s compare butter and sour cream here. Butter contains very little lactose (a sugar) whereas sour cream tends to contain 3-4w% of lactose. This will make a recipe with sour cream instead of butter brown a little faster in the oven! That said, the low acidity of sour cream will slow down the browning reaction again! What the final effect will be will depend on whether there are other sour ingredients as well (in which case the extra acidity of sour cream might be less important) or how much sugar is there in total.

Sour cream cake recipe

Overall, you will find that sour cream is often used to improve the texture of a cake and maybe to cut through some of the sweetness, thanks to its acidity. The photos in this post are of one such recipe that uses sour cream, it’s the hazelnut crumble cake from Yotam Ottolenghi. The original recipe also contains a glaze and crumble, but since we’re focusing on sour cream here, I’ll focus on the cake element.

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hazelnut crumble bundt cake

Why & how sour cream is used in cakes – Sour cream science

  • Author: Science Chef
  • Prep Time: 20 mins
  • Cook Time: 50 mins
  • Total Time: 1 hour 10 mins
  • Yield: 15 portions
  • Category: cake

Ingredients

  • 380g sour cream:full fat yogurt (as you’ve read, you can use both, we’d recommend a ratio of 2:1, but feel free to experiment!
  • 1,5 tsp baking soda
  • 3 eggs
  • 280g sugar
  • 250g butter
  • 1 tbsp brandy
  • 2 tsp vanilla extract
  • 460g flour
  • 2 tsp baking powder
  • 1/4 tsp salt

Instructions

  1. Mix the sour cream, yogurt and baking soda and leave on the side for approx. 15 minutes.
  2. Mix the eggs, sugar and butter. Ideally the butter is room temperature so it mixes in easily.
  3. Add the brandy and vanilla extract to the egg mixture.
  4. Carefully mix the sour cream mixture with the egg mixture. You can use a stand mixer at a low speed.
  5. Gently fold in the flour, baking powder and salt into the mixture. Do not mix for too long or you will start developing gluten which will make it less airy.
  6. Pour the batter in a Bundt cake pan.
  7. Bake in a pre-heated oven at 180C for 40-50 min.

Read the complete review of Yotam Ottolenghi’s book Sweet here. We’d definitely recommend it!

Sources

Dairy science and technology 2nd edition, P. Walstra et. al., 2005, link, p. 368 (Table 13.4) & 552

On Food and Cooking, Harold McGee

USDA national nutrient database, link

Maximizing food flavour by optimizing the Maillard reaction, Khymos blog, link

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