Caramel science – What happens when making a caramel?

Runny caramel sauce, chewy caramel bites, a caramel layer in an ice cream or an oozy layer of caramel in some Millionaire’s shortbread. All caramel, but all look different. Nevertheless, the basics of caramel making are the same for all. The same chemical reactions take place (Maillard reaction a/o caramelization for the experts) and the same types of ingredients are used.

It’s a fascinating and delicious product to make, so it’s time to discuss some caramel science!

What is a caramel?

The most simple caramel is nothing more than caramelized sugar. In other words, sugar that has been heated enough for it to brown and form all sorts of nice flavours and aromas. The most simple caramel starts with only sugar (and water, but even water can be left out). Caramels can also be a lot more complex, they might contain fats (butter for instance) or proteins (what about milk?).

Caramels are brown and have a lot of flavour. If a caramel has been heated to much it will not only turn black, it will also become more bitter.

The Caramel Making Process

There are a lot of different ways to make a caramel. Here we’ll stick with one process, not necessarily saying it’s the one and only, but it for sure has some good science behind it:

Step 1: Boiling/heating sugar – Using either the dry or wet method
Step 2: Sugar caramellization – Here’s where the sugar becomes brown
Step 3: Stopping the caramelization
Step 4: Adding other ingredients

Even though these four siple steps aren’t hard to do. Making caramel is actually pretty complex from a scientific perspective! Scientists still don’t completely understand what happens during this process. Luckily, you don’t need all that for making a good caramel.

Step 1: Boiling/heating sugar

The first step  when making a caramel is heating the sugar. A caramel can only be formed when the temperatures are high enough (that is, well above 100°C).

Heating pure sugar isn’t always easy at home with your tools, so there are two methods to do this:

  1. The dry method: using only sugar, nothing else
  2. The wet method: using sugar and water, this one is a little more fool proof and my go to method

The dry method

In this method you place sugar in a pot and heat it gently until it starts to melt and reaches the next stage: caramellization. However, if you don’t have good pots or an even heating stove this can proof more tricky. There’s a chance part of your sugar heats up faster than the other, causing part of it to burn whereas the rest is still far from browning.

Nevertheless, it is surely a way to do it.

The wet method

This more fool-proof way uses sugar and water. Take the same amount of sugar you needed for the dry method and add water. It doesn’t even matter how much water you add, however, the more you add, the longer it takes. A good guideline is to add enough to dissolve at least half the sugar at room temperature. The rest will dissolve once the water is heated up further. If for some reason you found out you’ve added too little (that is, not all sugar dissolves during the process as described further on), just add some more. It won’t do any harm at all.

So what happens during this process?

First of all, the sugar will dissolve in the water. The warmer the water, the most sugar can be dissolved in the water. By dissolving the sugar you make it easier for all the liquid to be heated evenly.

Once the sugar has dissolved you want to heat up the sugar further and get rid of the water. To do so, the sugar solution simply has to be boiled for long enough. The longer you boil it, the more water evaporates, the higher the concentration of sugar becomes and the hotter it gets.

At a point, the concentration of sugar will become very high. Because it is so high it will become very sensitive to crystallization. Stirring it can start this. You want to prevent that, so no stirring in your sugar solution here! Afraid of burning? Make sure you place your pan on a not too high heat and heat it evenly, swirl it if really necessary.

Step 2: Sugar caramellization

While heating your sugar solution, you are making it warmer and warm. Until it reaches the point that it starts to brown. This is the caramelization temperature. If you use pure regular sugar (sucrose), this will be at around 180°C. From this temperature onwards a lot of different chemical reactions will take place, making both aromatic compounds as well as brown colours.

This caramellization reaction is different from the Maillard reaction since it only involves sugar, nothing else. In a separate post I’ve written extensively about caramelization and the reactions occuring in this process.


Step 3: Stopping caramelization

Once your sugar is hot enough to caramellize, chances are it will burn if you don’t stop the process. It is so hot, that even just turning down the heat will not stop all reactions going on immediately. This can make the caramel just a little too dark or bitter.

Another thing to keep in mind here is that your caramel contains only a very little bit of water at this stage. No matter whether you used the dry or the wet method, the caramel will have <1% moisture. If you just leave this in a pot it will become a hard glassy structure. It’ll be impossible to eat.

An easy solution to solve both these problems is to add something to the caramel. You can add water, but also a fat (such as butter) or an ingredient like cream or milk. This extra ingredient (or several) does two things:

  1. It cools down the mass, stopping caramelization and preventing possible burns.
  2. It increases moisture content and makes the caramel softer at a lower temperature, instead of this rock hard bit.

caramel bars, millionaire shortbread, shortbread, caramel & chocolate

Step 4: Adding other ingredients

When adding other ingredients to the caramel once it has turn a nice golden brown (whether it be for cooling down or just the texture) keep in mind that the sugar is hot. Therefore, it is best to add in things that disperse easily throughout the caramel. For instance, for add your cream, than the butter. The cream will be easy to mix in, whereas the butter takes a little longer.

Also, there is a good reason for adding these ingredients after caramelization has taken place and not before.

There is another good reason that you shouldn’t add the cream and butter at the start when making caramel (so with the sugar & water). Since the sugar gets so hot, a lot of ingredients will simply burn during caramelization, that won’t taste great. Also, ingredients which have proteins in them (such as butter and cream) can initiate Maillard reactions. These will also lead to a brown product, but it has a different chemistry than that of a pure sugar caramel. Also, the product will burn at a lower temperature, things can prevent you from lowering the water content sufficiently.

Fixing a crystallized caramel

Sometimes, the sugar just crystallizes in the pot while heating it. The can be caused by just a few crystals on the side of the pan. You will notice the mixture starts to thicken and you might see lumps, these are sugar crystals. No worries though, this can be fixed quite easily. Just finish making your caramel until you’ve got the right colour.

Add all your ingredients for your recipe and add quite a bit of extra water. You will now have too much water, creating a runny caramel. Slowly heat the caramel back up and make sure all the sugar dissolves in the extra moisture. Once all the sugar is dissolved heat the caramel up to the desired temperature. This temperature will determine the find structure of the caramel (runny, gooey or brittle).

Making caramel – Recipes

After all that theory I can imagine you’re craving for some caramel now (or a pie with caramel). Here’s two for your to try!

Caramel recipes
Prep time
Cook time
Total time
Two recipes, both make a good caramel.
Recipe 1
  • 200g regular sugar
  • 60 ml water
  • 80 ml cream - high fat content
  • 4 drops of vanilla
  • 50g unsalted butter
  • ⅛ tsp salt
Recipe 2
  • 200g cream
  • 280g sugar
  • 120g butter
Recipe 1
  1. Put the sugar and water in a pan, place on a medium/high heat. Take it from the fire once it has turned a nice brown colour. Do not stir, read below why.
  2. Add the cream immediately, take care, it will bubble a lot and it will be very hot.
  3. At the vanilla, salt and butter. Stir until all the butter has melted.
Recipe 2
  1. Mix the cream, sugar and 80g of butter in a pan. Take quite a large pan, when the cream starts boiling it will rise quite a bit.
  2. Place on a medium/high heat and keep on heating until the caramel has turned the right colour. Stir regularly to prevent the cream from sticking on the bottom.
  3. Once you've reached your desired colour, turn off the heat and add the remaining butter. Stir until all the butter has melted.
  4. The reason for keeping back some butter here is to cool down the mixture and prevent further browning. You could add all at the start but then there's no way to stop it if it's just gone a little too far.



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