Why Cheese Fondue Splits & How to Prevent it

After searching for and buying the right types of cheese, you’re finally ready to start making your cheese fondue. You enthusiastically add the cheese to that special cheese fondue pot, only to end up with a mess of stringy, clumpy cheese a few minutes later! What happened?!

It definitely happened to me, and it’s so disappointing. Luckily, there’s some real science behind that clumpy cheese. Casein proteins are responsible for that stringy network. To prevent it, all you need are some patience, acid, and, possibly, a little starch!

Stringiness is caused by caseins

The large, undesirable clumps in cheese fondue can all be traced back to one ‘culprit’: casein proteins. Casein proteins are one of two major types of protein present in cow’s milk – the other being whey. Thanks to casein proteins, milk can curdle. And it’s those curds of casein proteins that form the basis of cheese. However, in cheese fondue, these curds can ‘misbehave’ and form undesirable clumps and lumps.

But you can’t just take out the casein. You’ll have no cheese left. Instead, to prevent clumpy cheese fondue, you’ll need to learn how to deal with these finicky proteins. Because, if treated well, they won’t be in your way at all.

Casein proteins can form networks

Casein proteins, just like any other protein, are long strands of amino acids. They’re like long necklaces, with individual amino acids making up the beads. These beads aren’t ‘passive’ though, they can interact with their environment. They can interact with each other, for instance, they might repel, or attract one another. Or, they can interact with other components present in the cheese fondue.

When cheese is melted, proteins can move around more freely and re-organize themselves. Some amino acids on those chains may interact with calcium, which is naturally present in cheese. Casein proteins (at a high enough pH) are negatively charged, whereas calcium ions are positively charged. That means, they attract one another. They align themselves and form large networks in which several proteins align and connect. These networks are what make a cheese fondue stringy. The more tightly bound the protein + calcium network is, the more stringy the cheese.

In a cheese fondue, you do not want these networks to form. Luckily, there are ample strategies you can use to prevent it from happening.

Choose the right type of cheese

The first strategy to apply is to choose a cheese that is well suited for making cheese fondue. Traditionally, cheeses such as (Swiss) Gruyère, Comté (very similar to Gruyère, but French), Emmentaler, and Appenzeller cheese are used. These cheeses have a good flavor profile, crucial to make a delicious fondue, and aren’t that prone to clumping (though if mistreated, they still can!).

Ripening breaks up proteins

Generally speaking, it’s best to use cheeses that have been ripened for a longer period of time. That is, after manufacturing, they’ve been laid down to rest.

During ripening a wide range of chemical reactions occurs. These improve the flavor of the cheese, but also change its structure. For instance, enzymes, a special type of protein, will cut up casein proteins into smaller pieces. When the casein proteins are smaller, it’s harder to make large interconnected networks. The strands simply can’t connect in as many places. And that reduces the chances of stringy fondue significantly.

Whether or not cheese has ripened is often mentioned on a label. Fresh cheeses such as paneer and quese fresco haven’t undergone any, or very little, ripening, and definitely aren’t suitable for cheese fondue.

This is also one of the reasons why you’d generally use a very different type of cheese to top your pizza or quiche than to make cheese fondue. For topping a pizza most people do want stringiness!

Fat, water, and salt keep caseins apart

Apart from choosing a ripened cheese, you’d also want one with reasonable amounts of fat, water and salt. Fat serves as a lubricant between all those casein proteins, so helps prevent that network from forming. Water has a similar role, though if your cheese doesn’t contain much of it, you can easily make up for it by adding more water to your fondue, more on that later.

Lastly, salt also helps to prevent those large protein networks from forming. They can take up the place of some of the calcium ions, inhibiting the formation of a strong sturdy network. Most ripened cheeses do contain a good amount of salt, so this is not necessarily an easy characteristic to base your choice of cheese on, but from a scientific point of view it shouldn’t be neglected.

Acid removes calcium during cheese making

A final cheese characteristic that can be important, is whether or not (a lot of) acid was used during manufacturing. There are a lot of different ways in which to make cheese. Some of these methods involve adding acid to the milk to help it curdle. The acid takes out some of the calcium. As a result, these types of cheese naturally contain less calcium. So, they’re less prone to stringiness.

This is not something that is typically given on a type of cheese, so checking with a cheese expert would be the best way to find out.

Do only European cheeses work?

Cheese fondue originated in Europe, more specifically, in the Alps. As such, you’d find that most recipes use cheeses that stem from that region. However, that does not mean that only those cheeses work! Feel free to experiment with cheeses that may be similar in style to the ‘original’ ones, but that aren’t ‘original’.

Wine and starch help keep it together

Just cheese doesn’t make fondue. As a matter of fact, a good fondue is a diluted version of melted cheese. Adding extra liquid is crucial to make the cheese liquid enough to dip, while still thick enough to coat whatever you’re dipping within.

Traditionally, wine would have been used to make cheese fondue. And there are some good reasons to stick with wine, and not just replace it with water.

Wine is a slightly acidic liquid, which means it lowers the pH-value of a liquid. This again has an impact on the net charge of proteins. We won’t go into detail on the theory here, but it’s helpful to know that at a pH-level of 4.7 (which is slightly acidic) casein proteins have a net charge of zero. As a result, they can’t interact with the positively charged calcium ions as easily anymore, thus preventing stringiness!

Wine happens to be of a very desirable acidity level. If you’d use pure vinegar or lemon juice for instance, which are both more acidic, you’d run the risk of making the liquid too sour. Not only would this make the cheese fondue less appetizing, it can also make the casein proteins less stable again.

A good rule of thumb for a wine:cheese ratio is 1:2 (weight based). So for 200g of cheese, you’d need 100g of wine.

The alcohol in wine doesn’t play a noticeable role in the fondue. As a matter of fact, if you gently heat the wine for some time before adding the cheese, most of the alcohol will evaporate.

Don’t skimp on flavor!

Since cheese fondue only contains a few ingredients, it’s just as important to choose a good tasting wine as it is to choose a good cheese. We made fondues with generic, bland white wines and they simple didn’t turn out as good as ones made with strong, slightly sour white wines.

Cheese fondue is a great way to use up a bottle of ‘old’ wine. It’s probably turned a little sour, but that’s ok, it adds flavor. If you’re unsure, taste the wine before making the fondue!

Starch makes it foolproof

You can definitely make fondue with only wine and cheese. However, if you want some more security against a stringy cheese fondue, starch may be your best friend. Corn starch or potato starch, or even wheat flour, they all work fine.

When you add starch to water and heat it, it will absorb and bind water (through a process called gelatinization). This starchy slurry then coats proteins and fat. This ensures they stay apart and thus they can’t form clumps.

Also know that as long as you only use a small amount of starch, the impact on flavor and texture is negligible.

Pre-made fondues contain some ‘secrets’

If you don’t want to risk making a stringy fondue, another alternative is to buy ready-to-heat cheese fondue. These sachets contain all the ingredients you need to make a cheese fondue. All you need to do is heat them up and maybe add some water. If you look closely at the ingredient list you will notice that aside from the expected cheese, wine and starch, they contain another ‘secret’ ingredient: phosphates.

Phosphates are a type of emulsifier and they help the cheese to melt into a gooey consistency. It makes the cheese fondue even more foolproof, with minimum chances of it splitting.

Processed cheese to the rescue?

You may have also come across cheese fondue recipes that use some sort of processed cheese. Processed cheese is made by mixing cheese with several other ingredients, one of them being phosphates! As such, adding a little bit of processed cheese uses the same trick as those cheese fondue manufacturers use. The phosphates stabilize the fondue, without significantly affecting the flavor!

Optimize the process

Even the best ingredients can still make stringy cheese fondue. Next up is managing those ingredients well, to reduce your chances of those protein networks from forming.

Keep in mind that to reduce the chances of cheese networks from forming we want to:

• make sure there’s enough liquid, so there’s some space between the proteins
• ensure the pH is low enough to limit casein:calcium interactions

Add the liquid first, then the cheese

It’s why you never start by adding cheese to a pot before adding the liquid. Instead, first, add the slightly acidic liquid (aka wine), warm it up and only then start to gradually add the cheese. ‘Gradually’ is crucial here, a little bit of patience will go a long way.

As soon as the cheese touches the warm liquid, the fat in the cheese will start to melt. As a result, the proteins get more freedom to move and they can gradually spread out within the liquid.

Grating makes fondue life easy

It can take a long time for a chunk of cheese to melt. What’s more, as long as it’s not fully melted, it can’t really spread out and the risk of it clumping is big. It’s why using grated cheese makes your life a lot easier here. In grated cheese the individual strands heat up quite evenly, making it easy to melt completely. What’s more, there’s plenty of water to surround every piece of cheese, again, reducing the chances of large networks being formed!

Don’t overheat or stir excessively

Whereas most fondues aren’t that susceptible to splitting, it is generally best to keep heating and stirring to a minimum. The warmer the proteins in the cheese get, the more they shrink. As a result, they expel water and this can cause the formation of clumps. It’s why it’s best not to continue boiling the cheese fondue once it’s done. First, you’re evaporating a lot of water, concentrating the protein, and you’re tightening the protein. Again, this doesn’t mean you can’t bring it to a boil, just don’t overdo it.

Secondly, you definitely need to stir to make cheese fondue. You need to spread out the grated cheese and make sure it melts homogeneously. However, don’t overdo it. No fast rapid whisking, a gentle stir with a wooden spoon tends to do the job just fine. Over stirring can again help proteins to align and form networks, thus making stringy cheese fondue.

Sources

Harold McGee, On Food and Cooking, 2004, p. 64-66; read our review

Emmi fondue original, from ah.nl

Pascal Bertsch, Laura Savorani, and Peter Fischer, Rheology of Swiss Cheese Fondue, ACS Omega, 2019 4 (1), 1103-1109, DOI: 10.1021/acsomega.8b02424 (open source), link

The PhCheese, Gruyère and Comté: Two of a Kind, Nov-15, 2016, link

https://www.theguardian.com/lifeandstyle/wordofmouth/2017/feb/09/how-to-make-the-perfect-fondue

https://www.cheesescience.org/calcium.html

https://www.cheesescience.org/fondue.html