Why zucchini makes a moist chocolate cake

We are facing a zucchini overload. Our two courgette plants have been giving us a new courgette at least twice a week. As a result, we’ve been eating a lot of courgette. So much so that we just didn’t feel like them anymore. After giving some away, preparing to make some into a soup that can be frozen, a great new solution came our way. A sweet snack with zucchini (or courgette as we call it). It sounded like the perfect solution we needed after days of pasta with zucchini, zucchini from the oven and plenty of other zucchini applications.

Even better, that sweet recipe was a chocolate pie (yes, it’s the cake at the top of this post, can’t see any zucchini anymore can you?). Never thought of zucchini and chocolate as a good combination? Think again. This zucchini chocolate cake was super moist and jummy.

Introducing: zucchini

Zucchini is a close relative of pumpkin and squash and grows on short plants with huge leaves. If you plan on growing zucchini (which isn’t the hardest  vegetable to grow), make sure you’ve got at least 1,5×1,5m of space for them. Once the plant starts growing zucchini you will first see a yellow/orange flower. After flowering most fall off quite quickly. These flowers can be used in cooking (thanks Masterchef Australia for that insight), but won’t keep long. At the bottom of this flower is where the zucchini grows, within a couple of days it’ll be ready for harvest.

A zucchini, as do most vegetables, mostly consists of water. Well over 90% of a zucchini is water. The remainder of a zucchini are some sugars and other carbohydrates, a little protein and several vitamins and minerals (source).

Vegetables and fruit can hold on to their water quite well, as long as the original structure is still intact. The cells and the concept of turgor will keep a vegetable firm and fresh. At this point, water might evaporate, but it will take a while. However, once you start cutting, grating, or otherwise breaking down those cells, the structure of a vegetable can change quite rapidly, especially for a vegetable like a zucchini which doesn’t have a very strong structure (as opposed to carrots for instance).

Baking with zucchini

The moisture loss also occurs for zucchini, when it’s grated, sliced or cooked. Once zucchini is grated, it can lose quite a lot of moisture easily. If you’d store grated zucchini in a bowl you can end up with a layer of moisture and some dry zucchini strands on top. By cooking/heating the zucchini you will accelerate that even further, breaking down cell walls and helping water leave the vegetable more easily.

When baking with zucchini you should keep that in the back of your mind. Do you want that water to come out of the zucchini during baking? If not, is there a way you can get rid of it on forehand? In other cases (such as this chocolate zucchini cake) you do want the moisture in your cake, it makes it even more moist.

Just like carrots and pumpkins, zucchini can be found in both savoury and sweet recipes. Carrots and pumpkin tend to be used in a cake to increase sweetness and flavour of the cake. Pumpkin will also thicken a pie filling. Zucchini on the other hand is quite bland in flavour, it thus isn’t so much used for its flavour, although it can certainly be highlighted by a proper use of herbs and spices.

flowering courgette zucchini plant
A flowering zucchini flower, at the bottom of the flower is where a zucchini has started growing.

Zucchini and moist cakes

Some like their cakes a little crumbly and slightly dry, others prefer a moist cake. There are tons of ways to make cakes and pies and also tons of ways to make them moist. It all start with properly baking and storing a cake to keep moisture inside. However, the other ingredients also play an important role.

As we discussed for a brioche bread, butter and eggs surely help to make a bread more moist. The same goes up for a cake. A cake without any fats, whether it’s oil or butter, will make more of a bread like product, and will be less moist.

In the case of this zucchini chocolate cake the amount of fat and eggs is also quite high, contributing to a nice moist structure. However, the zucchini surely contributes as well. Since a zucchini contains so much water it essentially contributes moisture to a cake. The batter itself might not look as fluid, but once the zucchini is heated, all moisture is released. Apart from that moisture, the fibers and carbohydrates in the zucchini, even though the content is low, will most likely help bind some water and keep the cake moist.

Zucchini disappears in the cake

After baking a cake with shredded zucchini you won’t be able to find the zucchini back in the cake, nor will it taste like it. The main reason for this is again that high moisture content. Most of a zucchini is water, so it will disappear into the cake and be soaked up by the flour and cocoa powder. Just like most vegetables, the structure of a zucchini breaks down because of the heat. The structures keeping up the cells will break down and soften. It literally disappears.

If you use thicker zucchini slices in a cake you might be able to find these back since they cannot dissolve as easily in their surroundings.

chocolate frosting on top of moist chocolate courgette zucchinie cake

Zucchini chocolate cake recipe

This recipe is strongly inspired by Sally’s baking addiction, it probably does contain a bit more zucchini. What’s interesting about the cake is that it is super moist, but pretty bland (since zucchini doesn’t really contribute a lot of flavour). Therefore it truly is best with a sweet frosting. If you like you cake fully covered in a thick layer of frosting, double the recipe, this recipe makes enough for a thin layer, just enough sweetness without it becoming overly sweet.

Why zucchini makes a moist chocolate cake
 
Prep time
Cook time
Total time
 
Recipe type: Cake
Serves: 1 large cake
Ingredients
Cake
  • 250g flour
  • 65g cocoa powder
  • 2 tsp baking soda
  • ½ tsp baking powder
  • ⅛ tsp salt (feel free to leave this out even)
  • 200g regular sugar
  • 190g butter
  • 50g vegetable oil (e.g. olive or sunflower oil, you can also substitute this for more butter)
  • 4 eggs
  • 80g plain yoghurt (skimmed or full fat will all work)
  • 2 tsp vanilla extract
  • 600g shredded zucchini (best to shred it very thinly, just 1 or 2 mm strands, it mixes in better)
Frosting
  • 140g butter (unsalted)
  • 210g icing sugar
  • 35g cocoa powder
  • pinch of salt
  • 1 tsp vanilla extract
  • 25g cream (or milk)
Instructions
Cake
  1. Mix together the flour, cocoa powder, baking soda & powder, salt and sugar.
  2. Melt the butter and add to the dry mix with the oil and eggs. Mix through, if you don't melt the butter it might form clumps in the dough, you'll need a little more patience before everything is mixed in.
  3. Add the yoghurt, vanilla extract and zucchini shreds, mix through.
  4. Take a round cake pan of 26 cm, line the bottom with baking paper and pour about half the batter into the cake pan.
  5. Bake in a pre-heated oven at 180C for approx. 25 minutes, test the cake with a toothpick, it should come out clean.
  6. Bake the second half of the batter if you have only one cake pan of the same size.
Frosting
  1. Mix the butter and icing sugar by hand using a spatula until the icing sugar doesn't dust any more. Than continue mixing with an electric mixer.
  2. Add the cocoa powder, salt, vanilla extract and cream and continue mixing until it has a smooth even consistency.
  3. Once the two cake halves have cooled down (really wait for them to cool, else the butter in the frosting will melt). Coat the bottom layer with a thin layer of frosting (if the cake has a dome on the top, cut of part of the dome to give a flat top layer). Place the second half on top and coat with the second layer of frosting. Best to give the top layer a bit more frosting than the bottom one, it will look nicer.

 

 

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