An almost golden brown colour, sweet, oozy or chewy, runny or firm, caramel can be found in all shapes and sizes. You can make a runny caramel sauce to poor over an ice cream, make some chewy caramel bites or swirled some into ice cream. Caramel can upgrade your creation to something even more special.
All made with just a few basic ingredients and a pretty similar preparation method. That said, caramel can be finicky, crystallizing when you don’t want it to do. Or it turns out too thick or thin. About time to dive into the science of caramel in order to help you make a perfect caramel and fix one when it all goes haywire. Caramel is super flexibly, hard to mess up completely, but it helps knowing what goes on to fix it up again.
What is caramel?
Even though there are a lot of caramel types, the basis is always sugar.* Caramel is brown, but it can vary from a light brown/orange colour to a very dark brown, closer to being black. This brown colour is formed during caramelization of the sugar. This caramelization also contributes to the flavour of caramel. Therefore, even though caramel is sweet, it has more depth of flavour. Caramel can actually be quite bitter and have a far more complex flavour profile.
Apart from sugar there are a lot of other ingredients that can be a part of caramel. The most common are milk, butter, cream, salt and water. These contribute to the richness of a caramel and the flavour profile, as we will come back to later.
*There are plenty recipes for caramel without any sugar, look-a-likes. But, since caramelization (the basis of any caramel, we’ll come back to it later) can only occur with sugars, the definition we’ll use here is that a caramel requires sugar.
How to make caramel
When making a caramel you are trying to achieve two things:
- Creating a nice brown colour (from uncoloured ingredients) through chemical reactions
- Creating the desired caramel consistency (whether it’s runny or firm)
Browning a caramel – caramelization
The nice brown colour of a caramel can be formed through the caramelization of sugar. By heating sugar to very high temperatures (regular sugar caramlizes at 160°C (320°F)) caramelization sets in. Caramelization is a series of chemical reactions in which the sugar participates. As a result of these chemical reactions larger molecules will form which have a brown colour.
Caramelization of sugar is done by heating the sugar without any other ingredients (except for water) to the correct temperature. At this temperature caramelization will set in and occur by itself, only cooling down the sugars will stop the caramelization again.
Browning a caramel – Maillard reaction
There is another way to form a brown caramel, without heating the sugar to these high temperatures. It is another very common chemical browning reaction in food: the Maillard reaction. During this reaction molecules with a brown colour are formed as well. However, instead of just sugar, this reaction also requires proteins to occur. Since butter, milk and cream contain these proteins, they can be added to sugar to initiate the Maillard reaction. Since this browning reaction will start to occur at far lower temperatures than caramelization, it is also used quite often in recipes.
Caramelizing sugar for caramel
You can caramelize sugar by heating it to temperatures well above the boiling point of water (160°C). As mentioned before, regular sugar (sucrose) will only caramelize at a temperature of 160°C. When making caramel at home there are two different ways to bring the sugar to this high temperature:
- The dry method: using only sugar, nothing else
- 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 subsequently start to brown, the caramelization. It is very important that all sugar it heated up evenly, else some might already brown, whereas other parts are still solid sugar crystals. This method tends to be more tricky than the wet method. However, it is quicker (you don’t have to evaporate all that water again) and it does give the same quality product.
The wet method
This more fool-proof method uses sugar and water. Instead of pouring the sugar in a pan by itself, you mix it with some water. The advantage is that the sugar will dissolve in the water. Since it is dissolved in the water it is easier to heat it evenly. While heating the sugar now, you’ll boil of the water. The more water that is boiled of, the warmer it becomes. Once the water has all evaporated the sugar is warm enough and caramelization will start.
It doesn’t matter how much water you add. Adding more water will result in a longer boiling time. If you don’t add enough water though, not all the sugar will dissolve. It is no problem to add extra water during boiling. It will just take more time.
Crystallization of sugar during caramelization
Regular sugar (sucrose), is quite special. When you buy a pack of sugar all the sugar will be crystalline, they are crystals. When making a caramel you do not want these crystals. Instead, you want to create a smooth consistency and crystals don’t belong there. This is why the wet method helps you in making a smooth caramel. It helps to melt the crystals by first dissolving them. That said, with both methods it is still possible to create those unwanted sugar crystals. Fortunately, they can be cleared away again quite easily.
So how do those sugar crystals form? Sugar molecules strongly prefer to sit in this crystalline structure. They only need a little help to recrystallize again when they are dissolved or melted. The higher the concentration of sugar, the higher the chance they will form these crystals again. This is why especially close to the caramelization temperature, when with both preparation methods there’s barely any moisture left, crystallization has a higher chance to occur.
There are a few tips and tricks to prevent crystallization of sucrose. The first is to add a crystallization inhibitor. This is an additional substance that can prevent sucrose from crystallizing. One of the most common inhibitors is glucose syrup. Glucose syrup isn’t only glucose. Instead, it also contains longer molecules. These molecules can interfer with the crystallization of the sugar, they will be in the way of the sugar molecules when trying to build a new crystal.
Sugar crystals tend to build up onto something. As soon as you have a crystal in your mixture, it will spread out very rapidly. These crystals will form more easily in a drier area (e.g. if some sugar sits on the wall of a pan where most moisture has evaporated) or on loose bits and pieces in your pan. A stirrer can also be an area where crystals start to grow. This is why most recipes will warn you to not stir the sugar while caramelizing, only do so at the start when the crystallization is not that likely to occur!
Solving crystallization in caramel
The easiest way to solve the crystallization (and the most effective) is to add more water. In other words, start over again. By adding the water, the sugar crystals can again dissolve. Simply re-heat the sugar, evaporate the water and try again!
Once you’ve succeeded to caramelize your sugar without having any sugar crystals, you will need to stop the caramelization again! Since the sugar is super warm at this point (remember, it’s about as hot as an oven!), the reaction will continue going for a while. The caramelization won’t stop immediately, even if you turn off the heat. As a result, the caramel may become way too brown or it might even burn.
That’s why most recipes will tell you to add something to the caramel to cool it down again. It can be as simple as adding some water. Often though you will see that you have to add some milk, cream or butter. The advantage of adding these into the hot sugar is that they will also participate in chemical reactions. This will improve the flavour of your caramel even further.
Always keep in mind that the sugar is very hot at this point. It is way easiest to add something liquid, this will mix in most easily. However, take care that it will boil almost immediately and it might therefore splash. If you add something with plenty proteins (e.g. milk or cream) take care that it will bubble up a lot.
Controlling caramel consistency
Caramels can be sauces, syrups or thick gooey bites. In most recipes you will first try to get the colour of the caramel right, before you focus on the consistency itself.
When you’ve just carmelized your sugar at 160°C to the right colour, the caramel contains <1% water. If you leave this to cool down it will become a rock hard piece of caramel. It might looks fancy, but there’s no way you’d be able to eat this without breaking off some teeth. The sugar has formed a glassy structure.
You can make it softer again by adding moisture. This can be water, but also milk or cream for instance, as long as water is added. Adding a lot of moisture will result in a sauce or syrup. Adding only a little bit of water will result in a thicker less runny caramel. The good thing about sugar and water though is that these are all reversible processes. If you’ve added too much water, simply bring the mixture to the boil and wait until the consistency is correct again. If you haven’t added enough, just add some more to make it thinner.
Caramel science troubleshooting
When a caramel has become grainy, the sugar has started to crystallize. If this always happens for your recipe, you might have to add some inhibitors as we discussed in the article. Adding inclusions into the caramel, for example peanuts, makes it more prone to crystallization and thus graininess. In those cases, you might want to take some extra measures.
A caramel can split if there’s fat in the caramel (e.g. from butter or cream). Often, a split caramel can be saved by gently reheating the caramel and stirring continuously. Adding some extra water can also help here to mix everything again before boiling off that extra water one more time. Last but not least, do not heat or cool down the caramel too rapidly. The fat might melt or solidify at a different rate than the caramel, causing the split.
Why caramel becomes (too) hard
No worries here! Just add some extra moisture, reheat and you will turn out with a thinner and softer caramel.
Can you freeze caramel?
Yes, you can, no problem. Take care to pack it airtight though. When you want to use or eat it take care to defrost it will in time. The caramel will have become pretty hard, so be patient before eating. Read more here on freezing caramel and its freezing point.
Applying caramel science – Recipes
After all that theory it’s time to get to work and make some caramel.
Or try these recipes! One uses the wet method to crystallize sugar, the other uses the Maillard reaction to create a nice brown sauce.
Recipe 1 - A smooth thick caramel, e.g. for caramel bars
- 200g regular sugar
- 60 ml water
- 80 ml cream - high fat content
- 4 drops of vanilla
- 50g unsalted butter
- 1/8 tsp salt
- 200g cream
- 280g sugar
- 120g butter
- 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.
- Add the cream immediately, take care, it will bubble a lot and it will be very hot.
- At the vanilla, salt and butter. Stir until all the butter has melted.
- 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.
- 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.
- Once you've reached your desired colour, turn off the heat and add the remaining butter. Stir until all the butter has melted.
- 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.