If you have ever sliced into a goat cheese and noticed a thin black line running through the middle, you have already met one of the most fascinating tools in cheesemaking: ash.

At first glance, it looks decorative. A dramatic contrast against snowy white curds. Something that belongs more in a modern restaurant plating than in traditional dairy craft.

But ash has been part of cheesemaking for centuries, and its role goes far beyond aesthetics.

In fact, ash affects pH, mould growth, texture, and flavour development. It can even help determine which microorganisms dominate the rind of a cheese.

In other words, that dusty grey coating is not just there for looks. It is quietly shaping the chemistry of the cheese.

Let’s dig into the science behind ash in cheesemaking and why cheesemakers continue to use it today.

What is ash in cheesemaking?

The ash used in cheese is typically food-grade vegetable ash, most often made from burnt grapevine cuttings or hardwood.

Modern commercial ash is usually purified activated vegetable ash, which means it is safe for consumption and extremely fine in texture.

Chemically speaking, ash is mostly composed of mineral salts, especially calcium and potassium compounds. These minerals make ash alkaline, which means it raises pH.

This simple chemical property turns out to be extremely useful in cheesemaking.

Historically, ash was originally used for practical reasons rather than visual ones. Cheesemakers discovered that applying ash to the surface of fresh curds helped control acidity and encouraged the right moulds to grow.

Today, many cheeses still rely on this same technique.

Why cheesemakers add ash

Ash plays several important roles in cheese development. Most of them relate to microbial ecology and pH control.

1. Ash reduces surface acidity

Fresh cheeses, especially goat cheeses, tend to be very acidic when they are first formed.

Lactic acid bacteria convert lactose into lactic acid during fermentation. This causes the pH of fresh curd to drop rapidly.

That acidity is important for coagulation, but it can create problems later. Many desirable rind microorganisms prefer a slightly less acidic environment.

Because ash is alkaline, applying it to the cheese raises the surface pH.

This small chemical shift creates conditions where beneficial moulds and bacteria can establish themselves.

Without ash, some of these microbes would struggle to grow.

2. Ash encourages mould development

One of the most important microbes involved in ash-coated cheeses is Penicillium candidum, the same mould used in cheeses like Brie and Camembert.

This mould forms a white bloomy rind and plays a crucial role in breaking down proteins and fats.

However, Penicillium candidum grows poorly in highly acidic conditions. If the surface pH is too low, it will struggle to colonise the cheese.

Ash helps by neutralising acidity on the rind, giving the mould a better chance to grow evenly.

As the mould develops, it begins metabolising lactic acid itself, further increasing surface pH and accelerating ripening.

This interaction between ash and mould is one of the most elegant examples of microbial succession in cheese.

3. Ash shapes rind development

Ash also affects the physical structure of the rind.

When dusted over fresh curds, ash absorbs surface moisture and creates a thin layer between the curd and the external environment.

This layer can influence:

• moisture migration
• oxygen exposure
• microbial growth patterns

The result is a rind that develops more evenly and supports specific communities of microorganisms.

This is particularly important in cheeses that rely on surface ripening.

4. Ash creates visual contrast

Of course, ash does have an aesthetic role too. The striking black or grey colour contrasts beautifully with white mould or pale goat cheese curd.

In some cheeses, ash is layered inside the cheese itself, creating a dramatic visual line.

These layers were originally practical. In traditional cheesemaking, ash was sometimes used to separate curds when multiple batches were combined.

Today, that line has become part of the cheese’s identity.

Types of ash used in cheesemaking

Not all ash is identical. Cheesemakers may use different sources depending on tradition and desired effect.

Vegetable ash

This is the most common type used today.

It is produced by burning plant material such as grapevine clippings, hardwood, or straw.

Vegetable ash produces a fine grey powder that spreads easily across cheese surfaces.

Activated charcoal

Many modern producers use food-grade activated charcoal.

Activated charcoal is extremely fine and consistent, which makes it easier to apply evenly.

Although technically slightly different from traditional ash, it performs a similar role in cheesemaking.

Historical wood ash

Before commercial ash was available, cheesemakers often used wood ash from hearth fires.

While this worked reasonably well, it could be inconsistent and sometimes introduced unwanted flavours.

Modern cheesemakers prefer purified ash because it provides predictable results.

Cheeses that traditionally use ash

Ash appears in many cheeses across Europe, particularly in goat cheeses.

Some of the most famous examples include:

Morbier

Perhaps the most recognisable ash cheese is Morbier.

This French cheese contains a distinctive black line running through its centre.

Historically, this layer of ash separated morning and evening milk batches. Farmers would press curd from the first milking, cover it with ash to protect it overnight, then add the second batch the next day.

The ash prevented contamination and insects while also helping regulate acidity.

Today, the line is mostly decorative, but it remains a defining feature of the cheese.

Humboldt Fog

One of the most famous modern ash cheeses is Humboldt Fog, produced by Cypress Grove in California.

This goat cheese features both a central ash line and an outer ash coating beneath a bloomy rind.

As the cheese ages, the centre remains dense and tangy while the outer layer becomes creamy and soft.

The ash helps encourage the development of the bloomy rind, which slowly ripens the cheese from the outside inward.

Sainte-Maure de Touraine

Another iconic ash cheese is Sainte-Maure de Touraine, a traditional French goat cheese.

This cheese is coated in ash and contains a straw running through its centre, which originally helped stabilise the log during ageing.

The ash contributes to the development of a delicate natural rind populated by yeasts and moulds.

As the cheese matures, the paste transitions from chalky and crumbly to creamy and smooth.

Does ash affect flavour?

Interestingly, ash itself contributes very little flavour to cheese.

Most people cannot taste ash directly. The quantity used is usually tiny, and the flavour impact is minimal.

However, ash indirectly influences flavour by shaping microbial growth and ripening dynamics.

When ash raises surface pH, it allows moulds and yeasts to become active earlier in the ageing process.

These microbes produce enzymes that break down proteins and fats through processes such as:

• proteolysis (protein breakdown)
• lipolysis (fat breakdown)

These reactions generate flavour compounds including:

• amino acids
• free fatty acids
• sulfur compounds
• aldehydes and ketones

Over time, these compounds create the complex aromas associated with surface-ripened cheeses.

So while ash may not taste like much on its own, it plays a quiet role in building the flavour architecture of the cheese.

The science of ash and cheese ripening

Ash also interacts with the internal chemistry of cheese during ripening.

When moulds grow on the surface, they begin metabolising lactic acid. This causes the pH of the cheese to rise from the outside inward.

This process is known as surface deacidification.

As the pH increases, enzymes become more active and begin breaking down casein proteins.

This leads to the soft, creamy texture typical of bloomy-rind cheeses.

Ash accelerates the early stages of this process by jump-starting surface pH adjustment.

Without it, the mould would take longer to establish itself.

Ash lines inside cheese

Ash is sometimes layered inside cheeses rather than applied externally.

These internal ash layers can serve several purposes.

Historically they were used to:

• separate batches of curd
• protect surfaces overnight
• discourage unwanted microbial growth

Today they are mostly used for visual appeal and brand identity.

The dramatic contrast between black ash and white curd creates a striking cross-section when the cheese is cut.

For cheesemakers, this visual cue also signals a particular style of cheese and ripening method.

Is ash safe to eat?

Yes. The ash used in cheesemaking is completely safe to consume.

Food-grade vegetable ash and activated charcoal are widely used in the food industry.

The quantities used in cheese are extremely small, and they pass through the digestive system without being absorbed.

In fact, activated charcoal has historically been used in medicine for its ability to bind toxins, although the amounts in cheese are far too small to have any therapeutic effect.

For most people, eating ash-coated cheese is no different from eating any other cheese rind.

Why ash remains popular today

Despite the rise of modern cheesemaking technologies, ash continues to be widely used.

There are several reasons for this.

First, ash helps control microbial ecosystems, which remain central to artisan cheese production.

Second, ash contributes to the visual identity of many cheeses. Consumers recognise these distinctive black lines and grey coatings.

Third, ash links modern cheeses to centuries of cheesemaking tradition.

What started as a simple farmhouse technique has become a hallmark of some of the world’s most beloved cheeses.

The quiet chemistry behind a dramatic look

Ash-coated cheeses might look dramatic, but their true beauty lies in the subtle chemistry happening beneath the surface.

A thin dusting of minerals changes the pH of the cheese. That pH shift determines which microbes thrive. Those microbes then shape the texture and flavour of the final cheese.

It is a reminder that cheesemaking is not just cooking. It is a careful orchestration of microbiology, chemistry, and time.

And sometimes all it takes to guide that process is a small pinch of ash.

Jonah Kincaid

Cheese lover. Scientist. Created a website and a Youtube channel about cheese science because he could not find answers to his questions online. 

cheesescientist.com

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