Tips for avoiding curdling

We get more calls about curdled food this time of year than any other time. Callers are frustrated when their homemade tomato soup curdles. It can be annoying when making tomato soup or scalloped potatoes to have the product look curdled and lumpy. It certainly is not an appetizing way to serve a meal.

You should know that the protein in milk is likely to clump together or curdle, when exposed to acid or salt. A number of things can help you avoid this situation. When making cream of tomato soup, try adding the tomato to the milk rather than the opposite. Remember to have both the milk and tomato hot, and thicken either the tomato juice or milk before they are combined. Do serve the soup promptly.

If you are baking scalloped potatoes, avoiding high oven temperatures and long cooking time will make the milk less likely to curdle. Parboiling the potatoes shortens the cooking time and the likelihood of curdling. Using evaporated milk further aids the product.

If ham and scalloped potatoes are baked together, curdling will occur. Ham contains curing salts, which make the milk protein extremely unstable and causes them to curdle easily.

Think through the recipe and directions before you start cooking; you should be able to avoid curdling in your dish.


Liz Meimann

I received both my undergraduate and graduate degrees in Food Science at Iowa State University. I love to quilt, sew, cook, and bake. I spent many years gardening, canning, and preserving food for my family when my children were at home.

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3 thoughts on “Tips for avoiding curdling

  1. i make a great stuffed shell dish with regatta cheese, mozzarella, basil ,salt, pepper, Italian seasoning, feta cheese, fresh chive, and bake it for 45 to 60 minutes, the results is always great one of our families favorites, but we like the regatta creamy and sometimes it is curdy we like it creamy why does the texture different from time to time? is it the bake time, I always bake it at 350 for 1 hour, please help.

  2. David, it is hard to tell exactly what the problem really is as it is not uncommon. To begin, I assume by regetta you mean ricotta. With that assumption, I will begin with understanding a little bit about ricotta. Ricotta is produced by coagulation of the proteins in the serum left from cheese production. This coagulation creates little blob of proteins which get strained. After straining, ricotta is rested to allow more liquid to run or drip off as it is the amount of liquid that is left with the cheese that determines how grainy the ricotta might be. Commercial ricotta may vary by brand as to how much the ricotta is drained to produce a desired weight for the carton. If you want a firmer, more velvety ricotta, place the ricotta in a cloth lined colander over a bowl and let drain overnight in the fridge. Further, heat causes the protein and water in the ricotta to separate, with the protein forming curds; this is more likely to happen with ricotta that is higher in moisture as the protein strands are farther apart.

    Now for some suggestions besides additional draining:
    Always use whole milk ricotta rather than a low fat version
    Cooks Illustrated suggests adding a small amount of cornstarch to the ricotta which coats the protein strands and helps prevent curdling
    Increase the amount of mozzarella
    Add an egg
    Mix the filling in a food processor to break the ricotta grains into finer pieces
    Use well-drained cottage cheese as an alternative

    I hope there is something in what I have shared that will help you produce the creamy texture you and your family desire.

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