They’re actually crystals, and far from being a problem, they’re a lovely sign that the cheese has been aged and is packed with flavour.

The main culprits

• Tyrosine crystals
  Tyrosine crystals are the ones you’ll spot most often. Tyrosine is an amino acid that shows up as the proteins in cheese gently break down during ageing. As time goes by, it forms those tiny white flecks that give a satisfying crunch when you bite in. You’ll find them in the likes of Parmigiano-Reggiano PDO, aged Gouda, Comté PDO, and Grana Padano PDO – all the big hitters.
• Calcium lactate crystals
  Calcium lactate crystals are a little less common, but they do like to pop up in aged cheddars. Sometimes you’ll find them tucked inside the cheese, other times they appear on the surface. The crunch is a bit different from tyrosine – but still very pleasing.

Why they form

As cheese matures, two main things are going on: the proteins and sugars are quietly breaking down.

• The cheese also slowly loses moisture, and as this happens, some of the compounds inside become less able to stay dissolved.
• Before you know it, those crystals start to appear.

It’s really just the cheese’s way of showing off that it’s reached a new level.

You might wonder: are these crunchy crystals safe to eat?

Absolutely! They’re not mould, not salt, and certainly not a defect. In fact, many cheesemakers are delighted to see them, as they’re a sign of long ageing and deep, developed flavour.

Flavour bonus

Those crunchy bits usually bring a few bonuses with them:

• Intense umami
• Brothy, savoury notes
• That moment when you think, ‘this cheese really means business.’

What tyrosine actually is

Tyrosine is an amino acid, one of the building blocks of proteins. In milk, proteins (mainly casein) are long, tightly folded chains. Fresh cheese keeps those chains mostly intact.

But in aged cheese, those protein chains don’t hang around for long.

How tyrosine forms in cheese

During aging, three big things are happening:

1. Proteolysis (protein breakdown)
   • Enzymes from rennet, starter bacteria, and other microbes get to work breaking down those long casein chains into smaller pieces. These are then broken down even further into individual amino acids.
2. This is when tyrosine is released and begins to accumulate
   • Tyrosine is released in relatively high amounts compared to other amino acids.
3. Crystallisation
   • Tyrosine doesn’t dissolve very well in water. As cheese ages, it loses moisture, becomes denser, and can even develop little pockets with a higher pH.

When there’s more tyrosine than the remaining moisture can cope with, it starts to settle out as crystals. That lovely crunch is actually just a solid form of an amino acid.

Why tyrosine crystallises (and others don’t)

Not all amino acids act like this. Tyrosine is a bit special because:

• It has an aromatic ring (bulky structure)
• It’s less water-soluble.
• It tends to stack up and line up, which is what gives you those visible crystals.

Other amino acids usually remain dissolved and contribute to flavour rather than texture.

What tyrosine crystals tell you

You can think of them as a little progress report from the cheese:

• Long aging (often 18+ months)
• Slow, controlled proteolysis
• Low moisture
• High-quality milk and make

That’s why you’ll spot them in traditionally made, hard cheeses, and not so much in the quick-aged, industrial sorts.

Texture & flavour impact

• Texture-wise, they give a sharp, brittle crunch – some people even call it ‘glass-like’.
• The flavour on its own is usually neutral or just a touch bitter, but the crystals tend to arrive with:
  • intense umami
  • brothy, umami notes
  • nutty aromas

The crystals aren’t what make the flavour, they’re just a sign that all the flavour-making chemistry has been hard at work.

Fun cheese-nerd detail

Under a microscope, tyrosine crystals look like:

• needles
• stars
• jagged shards

What Calcium Lactate Is

• Chemical formula: C₆H₁₀CaO₆
• It’s a calcium salt of lactic acid, which is produced during cheese fermentation when starter bacteria metabolise lactose.
• Essentially, it’s the cheese’s way of turning ‘calcium plus leftover lactic acid’ into little crystals.

How Calcium Lactate Forms in Cheese

1. Lactic acid production
   Starter bacteria in the cheese convert lactose (milk sugar) into lactic acid.
2. Calcium interaction
   Milk contains calcium naturally. Lactic acid can combine with calcium to form calcium lactate.
3. Supersaturation → crystallisation
   If the local concentration of calcium lactate exceeds how much can dissolve in the remaining moisture:
   • Crystals form
   • Often near the surface or along cracks, not as deep inside as tyrosine
4. Environmental factors
   • pH: more likely if the cheese is slightly more acidic
   • Moisture: lower moisture favours crystallisation
   • Temperature: can form during aging or even after packaging

Where You Find Calcium Lactate Crystals

• Aged Cheddar
• You might spot them on the surface or tucked into the cracks of a block.
• Less common in long-aged hard European cheeses (like Parmigiano) because those favour tyrosine instead

Texture & Taste

• The crunch is softer, more of a ‘pop’ than the brittle snap you get from tyrosine.
• The mouthfeel can be a little chalky, almost sugary.
• The taste is mostly neutral, though you might notice a faint mineral note.
• Often mistaken for tyrosine if you’re not careful, but the crunch and chalkiness give it away.

Fun cheese-nerd detail

• Calcium lactate crystals are sometimes visible as white or slightly translucent deposits.
• They can appear even on young cheeses if storage conditions favour supersaturation.
• Some cheesemakers even try to control crystallisation to avoid surface crystals in mild Cheddar, as some people still see them as a fault.

It’s amazing how much science goes into cheese, isn’t it?