Troubleshooting Homemade Cheese and Mozzarella: Common Problems and How to Fix Them

1. Curds Won’t Form or Are Too Soft

The Problem:
Instead of forming nice, firm curds, your milk stays soupy or forms tiny, fragile bits.

The Cause:

The milk might be ultra-pasteurised (which alters the milk proteins so they can't form proper curds).

Temperature control might be off — too hot or too cold when adding rennet.

Weak or expired rennet.

The Fix:

Always use fresh, non-ultra-pasteurised milk if possible. Local milk, organic milk, or milk labeled simply “pasteurised” works best.

Use a thermometer and be precise with your temperatures, especially around 32–38°C (90–95°F). Although our recipes are using the Thermomix temps as a guide, you can also use a thermometer to be more precise. I have selected 40°C as a guide, because warming 2L of cold milk for 10 minutes is probably going to result in around the 38°C mark. Don't NOT follow the recipe if you feel that the 40°C has not been reached. Proceed as directions explain.

Make sure your rennet is fresh and stored correctly. If in doubt, increase the amount slightly. Vegetarian rennet which is most common nowadays, can be more problematic. Using slightly more than the recipe states, may help. 

2. Curds Are Too Tough or Rubbery

The Problem:
The curds form, but they’re tough, rubbery, or difficult to stretch when making mozzarella.

The Cause:

Overheating the curds during the process.

Too much rennet.

Over-acidification (waiting too long before processing the curds). Set the timer! 

The Fix:

Heat gently and slowly during the stretching phase. Target around 75–80°C (170–176°F) for mozzarella stretching.

Measure rennet carefully — a little goes a long way!

Don’t let the curds sit too long before proceeding. Keep an eye on pH if you can: mozzarella stretches best when the pH is around 5.2–5.4.

3. Curds Disintegrate or Fall Apart

The Problem:
Instead of forming together, your curds crumble and fall apart when handled.

The Cause:

Cutting the curd too early (before it has firmed).

Rough stirring or handling.

Using milk with low protein content.

The Fix:

After adding rennet, allow the curd to set fully (the clean break test: insert a clean knife — the curd should split cleanly).

Stir gently after cutting the curd to avoid breaking them apart.

If using store-bought milk, sometimes adding a small amount of calcium chloride (diluted in water) before rennet can strengthen curd formation.

4. Cheese Is Grainy or Dry

The Problem:
Your finished cheese feels grainy instead of smooth and luscious.

The Cause:

Overheating the curds.

Handling the curds too much.

Not enough moisture retained during stretching.

The Fix:

Keep the temperature lower and slower.

Handle the curds minimally — treat them like delicate clouds!

During mozzarella stretching, don't overstretch. Fold it gently just a few times for a silky finish.

5. Mozzarella Won’t Stretch

The Problem:
No matter how much you heat or pull, your mozzarella just breaks apart.

The Cause:

The curds are either too cold or not acidic enough.

The Fix:

Make sure the curds are fully heated (again, 75–80°C).

If pH is too high, the curd won’t stretch. Next time, let the curds sit a little longer before stretching to allow for more natural acid development, or adjust with a small addition of citric acid at the beginning.

6. Cheese Tastes Bitter

The Problem:
Everything looks right, but the cheese has an unpleasant bitterness.

The Cause:

Too much rennet.

Insufficient draining of whey.

Poor milk quality.

The Fix:

Measure rennet carefully and never guess.

Drain whey thoroughly but gently.

Start with fresh, high-quality milk whenever possible.

A Few Bonus Tips for Cheese-Making Success

Cleanliness is critical: Any contamination can ruin your batch. Always sterilise your equipment.

Patience pays off: Rushing through the steps can cause all sorts of problems. Give each stage its time.

Keep good notes: Every batch will teach you something. If something goes wrong (or fantastically right!), knowing what you did can help you recreate or adjust.

Making cheese at home is a little bit of science, a little bit of art — and a lot of delicious fun. Even when things don't go exactly as planned, each batch teaches you something new. Keep practicing, stay patient, and soon you’ll be making creamy, stretchy, perfect mozzarella (and more!) like a pro.