Why Does My Mac & Cheese Curdle?

Struggling with curdled mac and cheese? We’re here to help. Let’s go over the reasons and get you back to creamy goodness.

There’s really nothing more disappointing than having the sauce for your mac and cheese curdle.

The good news is that, first, curdled mac and cheese is easy to fix, and second—with a little knowledge, which this article is all about—it’s also very easy to prevent it from happening in the first place.

So keep reading to find out what causes mac and cheese to curdle and how to make sure it never ever happens to you again.

Why Mac & Cheese Curdles

The best mac and cheese sauce is thick and creamy. But achieving that without curdling can be tricky, especially if you’re not yet a pro at making this classic dish.

The cheese sauce for your macaroni and cheese dish can curdle for three reasons: either the milk was too old, the cheese wasn’t grated finely enough, or it was heated too quickly at too high a temperature.

Heat hastens the curdling of milk caused by bacteria. And the older a carton of milk is, the more bacteria it contains—so always use fresh milk for your mac and cheese sauce.

Then there’s the cheese. Finely grated cheese melts quickly and has time to blend with the milk before it gets overcooked and starts to curdle. Cubed cheese or thickly grated cheese, on the other hand, doesn’t. Remember to grate your cheese as finely as your grater allows.

Lastly, excessively high heat can cause the cheese to curdle quickly. To reduce the risk of curdling, always make your mac and cheese sauce off the heat, right after you’ve made the roux, using the residual heat of the saucepan.

How to Keep Mac & Cheese From Curdling

Okay, now that you know what causes mac and cheese to curdle, how can you prevent it from happening in the first place?

The keys to making a perfectly creamy and smooth mac and cheese sauce are to use fresh milk, shred the cheese using the finest side of the grater, and to mix in the cheese with the milk away from the heat.

Of course, the devil is in the details, and there’s a bit more to it than that. So let’s walk you through the process of making the perfect mac and cheese step by step.

Here’s how to get your mac and cheese game right:

1. Grate the cheese. Grate sharp cheddar cheese using the finest setting on your cheese grater and set it aside.
2. Cook the macaroni. Bring a pot of generously salted water to a full boil over high heat. Add the macaroni, reduce the heat to medium-high, and let it cook.
3. Make a roux. Melt butter over medium heat in a saucepan, then mix it with all-purpose flour and cook, stirring occasionally, for 1 minute.
4. Add the milk. Whisk in whole milk and bring to a boil. Reduce the heat to medium-low and simmer to thicken, stirring occasionally, for 5 minutes.
5. Add the cheese. Remove the pot from the heat and wait 30 to 45 seconds for it to cool down slightly. Whisk in the grated cheese and your spices.
6. Combine the cheese with the macaroni. Drain the macaroni and mix it with the cheese sauce. You dish is ready for serving.

The result?

Mouthwatering, picture perfect mac and cheese without curdling. But don’t just take my word for it—give it a try and then let me know how it went by coming back and leaving a comment below!

How to Fix Curdled Mac & Cheese

The best way to fix curdled mac and cheese depends on the extent of the curdling. So let’s explore all the ways to salvage your dish.

1. Add a splash of liquid. Remove the saucepan from the heat. Add a splash or two of the base liquid you used for your sauce—probably milk.
2. Run it through a sieve. Run the sauce through a strainer or fine-mesh sieve. Refrigerate the curdled parts of the sauce and use them for something else.
3. Put it in the blender. A few seconds in the blender should make your cheese sauce perfectly smooth.

If unsure, start with the first method and proceed to the others in case it doesn’t work.

What Makes Mac & Cheese Creamy

It’s the cheese sauce that makes mac and cheese deliciously decadent.

A good cheese sauce can elevate your homemade mac and cheese to a whole new level—and a curdled one can completely ruin the look and mouthfeel of your dish.

The trick is to get your ingredients right:

When making the roux, use equal parts butter and all-purpose flour, and don’t overcook it.

Choose whole milk. While we should all watch our calorie intake, macaroni and cheese is one of those dishes best enjoyed on cheat days, so make it accordingly.

Don’t just go for the cheapest cheese at the grocery store. For a creamy and rich sauce, you want sharp, aged cheddar, which melts in your dish like a cream.

Bottom Line

Mac and cheese curdles when you use milk that’s not fresh, grate the cheese too coarsely (or cut it into large blocks), or mix the cheese with the thickened milk over too high heat.

To keep your mac and cheese from curdling, use fresh milk, grate the cheese finely, and mix the cheese with the thickened milk away from the heat, after allowing the pot to cool down a bit.