If you’ve ever cut into a wedge of blue cheese and noticed the tiny tunnels, cracks, or pinprick holes running through it, you’ve already met one of the most important features in blue cheesemaking.

Those holes are not mistakes. They are not “bad ageing”. And they’re definitely not there by accident.

In fact, without them, most blue cheeses simply wouldn’t be blue at all.

This post unpacks why blue cheeses have holes, how they form, what they do for flavour and texture, and why cheesemakers work surprisingly hard to control something that looks so chaotic.

Blue cheese is an oxygen problem (and a solution)

At its core, blue cheese is an exercise in oxygen management.

The mould that gives blue cheese its colour, aroma, and bite is Penicillium roqueforti. This mould is aerobic. That means it needs oxygen to grow.

Milk, curds, and pressed cheese are not exactly oxygen-rich environments. Once curds are formed and drained, they quickly become dense and low-oxygen. That’s great for many cheeses. It’s terrible for blue mould.

So cheesemakers had to solve a problem:

How do you get oxygen deep inside a cheese without breaking it apart?

The answer is holes.

The holes are air highways for mould

Those small openings inside blue cheese act as oxygen channels.

They allow air to move from the outside of the cheese into the interior. Along those air paths, Penicillium roqueforti wakes up, grows, and produces the familiar blue-green veins.

Where there is oxygen, mould grows.
Where there isn’t, it doesn’t.

That’s why blue cheese doesn’t turn uniformly blue. Instead, it forms veins, streaks, and pockets that follow cracks and air spaces. The mould is literally tracing the cheese’s internal airflow.

Holes come before veins

A common assumption is that blue mould somehow creates the holes.

It doesn’t.

The holes come first. The mould follows.

During early cheesemaking, blue cheeses are handled much more gently than pressed cheeses like Cheddar. Curds are often loosely packed into moulds rather than pressed hard together.

This leaves behind:

• Small gaps between curds
• Irregular cracks
• Micro-pockets of trapped air

These spaces later become the scaffolding for blue mould growth.

If the curds were pressed tightly and fully knit together, oxygen would be excluded. The mould would suffocate. You’d end up with a dense white cheese with no blue character.

Piercing: the moment the holes really matter

Most blue cheeses are pierced during ageing.

This is when long stainless-steel needles are pushed through the wheel or cylinder of cheese. Dozens of holes are made in a deliberate pattern.

This piercing step serves two purposes:

1. It introduces fresh oxygen into the interior
2. It connects existing air pockets into continuous channels

Think of it like ventilation.

Once pierced, air can move freely through the cheese. Dormant mould spores inside the paste suddenly have access to oxygen. Growth accelerates. Veins expand outward from the pierced holes.

Without piercing, blue development would be weak, patchy, or confined to the surface.

Not all holes look the same

Blue cheese holes aren’t uniform, and that’s intentional.

Different styles aim for different internal structures.

Some blues have:

• Fine, hairline cracks
• Small pinholes
• Delicate marbling

Others have:

• Large cavities
• Chunky blue pockets
• Dramatic internal landscapes

These differences come down to curd size, moisture, handling, and how aggressively the cheese is pierced.

A more open structure allows faster mould growth and bolder flavour. A tighter structure slows things down and keeps the blue more restrained.

Holes shape flavour, not just appearance

Blue cheese flavour isn’t only about mould being present. It’s about what the mould does once it has oxygen.

As Penicillium roqueforti grows, it produces enzymes that break down:

• Milk fats (lipolysis)
• Milk proteins (proteolysis)

These reactions generate many of the compounds we associate with blue cheese:

• Peppery notes
• Savoury depth
• Mushroomy aromas
• That unmistakable piquant, tingling finish on the palate

The more oxygen the mould gets, the more active these reactions become.

That means holes don’t just enable blue veins. They actively control flavour intensity.

Fewer holes. Milder blue. More airflow. Bigger personality.

Texture depends on those air pockets too

Blue cheese texture is closely tied to its internal openness.

The breakdown of fats and proteins near air channels softens the paste. That’s why blue cheeses often feel:

• Creamy near veins
• Crumbly yet yielding
• Softening from the inside out

If oxygen were evenly distributed (which it never is), the cheese would mature uniformly. Instead, you get contrast. Firmer areas sit next to buttery, breakdown-rich pockets.

Those textural shifts are part of the appeal. Each bite changes depending on where it lands relative to a vein or cavity.

Why blue cheese holes aren’t “eyes”

It’s worth clearing up a common misconception.

The holes in blue cheese are not the same as the eyes in Alpine-style cheeses.

Eyes in cheeses like Emmental are formed by carbon dioxide produced by bacteria during fermentation. Gas builds up, stretches the paste, and creates round, glossy holes.

Blue cheese holes are different:

• They’re irregular, not spherical
• They’re formed mechanically and structurally
• They’re designed for airflow, not gas expansion

If blue cheese relied on gas production to create holes, the structure would be unpredictable and often destructive. Instead, cheesemakers build openness into the curd from the start.

Too many holes can be a problem

More holes are not always better.

If a blue cheese is too open, several things can go wrong:

• Excessive moisture loss
• Overly aggressive mould growth
• Bitter or metallic flavours
• Structural weakness

Cheesemakers walk a fine line. They want enough airflow for healthy blue development, but not so much that the cheese collapses under its own enzymatic enthusiasm.

This is why blue cheesemaking is as much about restraint as it is about encouraging mould.

Some blue cheeses hide their holes better

Not all blue cheeses advertise their internal architecture.

Some styles have:

• Tighter pastes
• Smaller, more evenly distributed air channels
• Subtle veining

Others are proudly chaotic inside.

The difference often comes down to milk type, moisture, and ageing conditions rather than mould strain alone.

A denser blue still needs oxygen. It just gets it through finer cracks rather than dramatic cavities.

What happens if you remove oxygen entirely?

If you vacuum-seal a young blue cheese before mould has fully developed, the result is telling.

Blue growth stalls. Veins stop expanding. Flavour development slows dramatically.

The cheese doesn’t spoil. It just pauses.

That’s because the mould can’t breathe.

Those holes and channels aren’t optional extras. They’re the difference between a living, evolving cheese and a frozen snapshot of one moment in time.

Blue cheese is engineered chaos

From the outside, blue cheese looks rustic and unruly. Inside, it’s even more so.

But the chaos is carefully engineered.

• Curd size.
• Packing style.
• Piercing patterns.
• Ageing humidity.
• Oxygen availability.

All of these variables determine where holes form and how the mould uses them.

What looks accidental is actually the result of hundreds of tiny decisions made by the cheesemaker.

So why do most blue cheeses have holes?

Because without them:

• The mould couldn’t grow
• The veins wouldn’t form
• The flavour wouldn’t develop
• The texture wouldn’t soften correctly

The holes are not flaws. They’re infrastructure. They are the breathing system of blue cheese.

And every vein you see is simply mould following the path of air, doing exactly what it has evolved to do.

The takeaway

Blue cheese holes aren’t there to look pretty. They aren’t signs of poor craftsmanship. They’re deliberate, functional, and essential.

They let oxygen in. They guide mould growth. They shape flavour and texture. Remove the holes, and you remove the blue.

If you enjoyed this kind of deep-dive into how cheese really works, you’ll probably like what I send by email. I share new posts, weird cheese science, and the occasional rabbit hole worth falling into.

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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

The post Why Blue Cheese Has Holes (It’s Not What You Think) appeared first on Cheese Scientist.

SEE ALSO: All the essential equipment you will need to make and mature your own cheese at home →

Why humidity matters for cheese ageing

Humidity influences how moisture stays in the cheese during maturation. If the humidity is too low, the cheese will dry out too fast, resulting in a cracked texture or a too-hard rind. Too much humidity, however, can encourage unwanted mould and spoilage.

Finding the right balance helps the cheese develop its desired texture, flavour and rind.

Effect of air humidity on cheese rinds

On a molecular level, air humidity affects the rind of cheese by controlling the movement of water molecules, influencing biochemical reactions, and impacting microbial growth. Here’s a breakdown of how humidity interacts with cheese at the molecular level:

1. Water molecule dynamics

Cheese contains water, fats, proteins and salt. When the humidity in the surrounding air is high, there’s a lower tendency for water to evaporate from the cheese’s surface. High humidity slows water movement out of the cheese, which keeps the rind moist and encourages the growth of specific moulds and bacteria.

In low-humidity environments, water molecules are more likely to evaporate from the cheese, leading to drying. This causes the proteins near the surface to denature and tighten, creating a harder and drier rind.

2. Protein and fat interactions

Humidity influences how proteins and fats on the cheese surface interact with each other and with water molecules. In a moist environment, casein proteins (which form a matrix in the cheese) can retain water, remaining flexible and preventing the rind from hardening too quickly. When proteins stay hydrated, they’re less likely to form dense cross-links, leading to a softer, more pliable rind.

In contrast, in low humidity, proteins and fats near the surface lose water, which increases the density of protein cross-links. This makes the rind harder and less permeable, which is desirable for certain hard cheeses but would hinder rind development in soft cheeses.

3. Microbial growth and metabolic activity

Cheese rinds are often home to various bacteria, yeasts and moulds. The availability of moisture from a humid environment supports microbial growth by allowing organisms to remain metabolically active.

Microbes, like Penicillium molds in blue and soft cheeses, require water to thrive and reproduce. When humidity is high, these microbes can grow steadily, breaking down fats and proteins and contributing to the flavour and texture of the rind and cheese.

In low-humidity conditions, the lack of moisture can reduce microbial activity, slowing down these biochemical processes. This affects not only the formation of the rind but also the development of complex flavours, since the bacteria and moulds responsible for flavour development become less active.

4. Salt and ionic interactions

Salt on the cheese surface interacts with water molecules, affecting osmosis and water retention. In high-humidity environments, salt ions attract water molecules, helping retain moisture at the surface and ensuring a more balanced rind development.

However, in low humidity, the water on the surface evaporates, leaving behind concentrated salt. This excess salt can inhibit microbial growth, resulting in a less complex rind. This is one reason hard cheeses, which benefit from a drier surface, can handle lower humidity without compromising their flavour.

Recommended humidity levels for ageing different cheese types

Each type of cheese benefits from specific humidity levels during ageing. Maintaining the right humidity is essential to control moisture loss, support microbial growth, and develop the desired rind and texture. Below are the ideal humidity ranges and their impact on each cheese type:

1. Soft White Mould Cheeses (e.g., Brie, Camembert)

• Recommended Humidity: 70% – 100%
• Why This Range? Soft white mould cheeses, often known for their bloomy rinds, require higher humidity to support the growth of Penicillium candidum, a mould responsible for the soft, velvety rind and creamy texture beneath. At lower humidity levels, the rind can dry out, hindering mould growth and potentially creating a hard or cracked surface.
• Impact on Flavour and Texture: High humidity allows these cheeses to retain moisture, creating a creamy, gooey interior as they ripen. The high-moisture environment also promotes the mild, buttery flavour typical of bloomy-rind cheeses.

2. Soft Washed Rind Cheeses (e.g., Taleggio, Époisses, Munster)

• Recommended Humidity: 80% – 95%
• Why This Range? Soft washed rind cheeses are washed in brine, alcohol, or other solutions to encourage bacteria like Brevibacterium aurantiacum, which produce the characteristic orange-red rind and pungent aroma. High humidity helps keep the rind moist, allowing these bacteria to thrive and develop the cheese’s unique flavour profile.
• Impact on Flavour and Texture: The bacteria that develop in high humidity create rich, earthy, and sometimes meaty flavours. The moisture levels also maintain a supple, soft rind and creamy interior, which are essential to the cheese’s texture.

3. Pressed Cheeses (e.g., Cheddar, Gouda, Parmesan)

• Recommended Humidity: 75% – 100%
• Why This Range? Pressed cheeses, which are often aged for extended periods, need moderate to high humidity to prevent excessive drying and cracking. The humidity level will vary based on the type of pressed cheese and its ageing needs: harder cheeses like Parmesan may be aged at the lower end, while semi-hard cheeses like Gruyère benefit from a higher humidity.
• Impact on Flavour and Texture: Moderate humidity levels prevent the interior from drying out too quickly while allowing the rind to harden gradually. This contributes to the development of a firm, smooth texture in Cheddar or Gouda and the crumbly, crystalline structure in longer-aged cheeses like Parmesan. Flavours also intensify as water evaporates more slowly in controlled humidity, allowing a full-bodied flavour profile to develop.

4. Blue Cheeses (e.g., Roquefort, Stilton, Gorgonzola)

• Recommended Humidity: 85% – 98%
• Why This Range? Blue cheeses contain blue or green moulds, typically Penicillium roqueforti, which grow within the cheese and on its surface. High humidity supports the development of these moulds by keeping the cheese moist and preventing the rind from becoming overly dry or cracked.
• Impact on Flavour and Texture: In a high-humidity environment, moulds penetrate the cheese, producing the characteristic blue veins and strong, tangy flavour. This moisture also keeps the cheese soft and creamy, enhancing the rich, spicy taste that blue cheeses are known for. If humidity drops too low, mould growth may stall, and the cheese can become excessively crumbly.

Want to learn more about what humidity range you need for specific cheeses? Click here for my comprehensive table.

How to monitor and control humidity for homemade cheese aging

To mature cheese at home, you need a reliable way to control humidity. Here are some key tools and tips to manage humidity for successful ageing.

1. Using a cheese cave or wine fridge

Many home cheesemakers use a wine fridge or dedicated cheese cave. These storage options allow you to set the temperature and monitor humidity levels, which is essential for cheese ageing. Place a hygrometer inside to check humidity regularly.

If your fridge doesn’t reach the desired humidity, try adding a bowl of water or using damp sponges to raise it. For reducing humidity, open the door slightly for brief periods to increase airflow.

2. Creating a DIY humidifying system

For those without a dedicated fridge, a simple plastic container can work for smaller cheeses. Place a small bowl of water or a damp cloth inside to increase humidity. Check daily to make sure your humidity stays steady.

A mini hygrometer can fit inside most containers to help track changes. Keep the container sealed tightly and adjust the water level or cloth dampness as needed.

3. Using ageing mats for surface moisture

Ageing mats help cheeses retain surface moisture and encourage even rind development. Mats made from bamboo or plastic are common, as they allow airflow while holding moisture on the surface. Mats are especially useful for soft and blue cheeses that need high humidity.

Remember to sanitise mats between uses to avoid unwanted mould growth.

Common challenges with cheese humidity

Humidity control can be challenging, especially in homes where temperatures and moisture levels fluctuate. Here are common issues and some quick fixes.

• Low humidity: If the cheese develops cracks or seems too dry, add more water inside the ageing container. A damp cloth or sponge can help boost humidity quickly.
• High humidity: If there’s excessive moisture or signs of unwanted mould, reduce humidity by removing any water sources, increasing ventilation or opening the container slightly for air circulation.
• Temperature changes: Changes in temperature can impact humidity. If your environment is inconsistent, consider moving the cheese to a more stable space or use a small fan to help with airflow and humidity control.

Different types of hygrometers

Here are some popular types of hygrometers suitable for ageing cheese at home:

1. Analog hygrometers

• Mason’s Hygrometer – Red Liquid IC736740: This traditional analog hygrometer includes a thermometer and is designed for accurate humidity measurement. It’s widely used in agricultural and food settings, making it suitable for cheese ageing where precision and durability are key.
• Brannan 12/413 Thermometer and Humidity Meter: This UK-made analog hygrometer is compact and reliable, featuring both a thermometer and a humidity gauge. It’s an affordable option for home cheesemakers who prefer a simple, battery-free device.

2. Digital hygrometers

• ThermoPro TP50: A compact digital hygrometer and thermometer with a clear LCD display. It measures temperature and humidity simultaneously, ideal for cheese ageing setups.
• Govee Smart Hygrometer: This model not only tracks humidity but also connects to a mobile app, allowing you to monitor conditions remotely. It’s great for those who want constant updates on humidity.
• Inkbird ITH-10: Known for accurate readings, this budget-friendly digital hygrometer is commonly used in home fermentation and cheese ageing. Its compact size is perfect for placing in tight spaces.

3. Smart Wi-Fi hygrometers

• SensorPush HT1 Wireless Thermometer/Hygrometer: This high-precision device connects to a smartphone app, offering real-time data and alerts. It’s highly rated for stability, accuracy and convenience, making it a great choice for serious home cheesemakers.
• AcuRite 06002M Wireless Temperature and Humidity Sensor: This Wi-Fi-enabled model allows you to check conditions via app, which is ideal if you’re monitoring cheese ageing in a remote cellar.

4. Hygrometer-thermometer combos with probes

• ThermoPro TP60: This hygrometer comes with a remote sensor and probe, allowing you to monitor humidity in difficult-to-reach spots. It’s suitable for deep cheese caves or containers where direct readings are tricky.
• Inkbird IBS-TH1: This model features a probe that can be placed directly inside a container, making it ideal for enclosed cheese ageing setups.

Final thoughts

Controlling humidity for cheese ageing takes practice, but the effort is worth it. With the right humidity levels, your cheeses can mature with the ideal texture, taste and rind. Start with a reliable hygrometer, track your humidity levels and make adjustments based on the cheese type.

Happy ageing, and enjoy the delicious results of your homemade cheese!

Cheese humidity table

References

Institut National de l’Origine et de la Qualité – https://www.inao.gouv.fr/

New England Cheesemaking Supply Co – https://cheesemaking.com/

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

The post How Much Humidity Do You Need For Ageing Homemade Cheese? appeared first on Cheese Scientist.

In this blog post, we will explore the scientific processes behind cheese maturation, the impact of time on flavour and texture, and why some cheeses mature in just a few weeks while others are aged for years.

The basics of cheese maturation (affinage)

Cheese maturation is a biochemical and microbial process. After curdling milk using rennet (or plant-based coagulants) to form the cheese, it is aged in carefully controlled environments, such as caves or temperature-regulated rooms. During this time, physical, chemical and microbial changes occur, transforming a fresh cheese into a complex, matured product.

Several factors influence the maturation process:

• Moisture content
• Temperature
• Humidity
• Microbial activity
• Time

Cheeses generally fall into two main categories based on their maturation:

1. Fresh cheeses (e.g., Ricotta, Cottage Cheese) are not aged or are aged only for a few days.
2. Aged cheeses (e.g., Cheddar, Gouda, Parmigiano Reggiano) mature for weeks, months, or even years.

Now, let’s dive into the scientific processes that occur during cheese maturation.

Proteolysis: the breakdown of proteins

Proteolysis is the breakdown of proteins into smaller peptides and amino acids, a fundamental process in cheese maturation. In the early stages of cheesemaking, milk proteins (primarily caseins) are coagulated by rennet, forming curds. As the cheese matures, enzymes from rennet, milk and microorganisms (bacteria, moulds and yeasts) continue breaking down these proteins.

How proteolysis affects flavour

Proteolysis plays a vital role in the development of cheese flavour. As proteins break down, they release a variety of compounds such as amino acids and peptides, which contribute to different flavours and aromas. For instance:

• Glutamate enhances the umami, or savoury taste, characteristic of many hard, aged cheeses.
• Tyrosine breakdown produces nutty, earthy notes commonly found in Cheddar.
• Methionine oxidation leads to the formation of sulphuric compounds, which can give washed rind cheeses like Gruyère an egg-like aroma.

In long-aged cheeses like Parmigiano Reggiano, the extensive breakdown of proteins creates a rich, concentrated flavour, while younger cheeses, such as Brie, have milder flavours as this process is less pronounced.

Proteolysis and texture

Protein breakdown also affects texture. In younger cheeses, proteins remain relatively intact, contributing to a firmer or creamier consistency depending on the cheese. As proteolysis progresses, the cheese becomes more crumbly or granular. This explains why older cheeses like Parmigiano Reggiano are hard and grainy, while younger cheeses like Brie remain soft and gooey.

In cheeses like Roquefort and Stilton, the breakdown of proteins and the action of moulds result in a creamier, more spreadable texture, even though the cheese may be aged for several months.

Lipolysis: the breakdown of fats

Lipolysis is the enzymatic breakdown of fats into fatty acids, another key process in cheese maturation. Milk fat is a crucial component of cheese, and the action of lipase enzymes breaks down triglycerides (the primary form of fat in milk) into free fatty acids, glycerol and other compounds.

Flavour development through lipolysis

Fatty acids produced during lipolysis contribute significantly to the flavour profile of aged cheese:

• Short-chain fatty acids, such as butyric acid, have strong flavours often described as bitter or pungent. These are characteristic of aged blue cheeses and some aged goat’s cheese.
• Medium-chain fatty acids produce a milder, more buttery flavour, contributing to the rich, smooth taste of cheeses like Gouda.
• Long-chain fatty acids are less volatile but can undergo further reactions, creating complex flavours with nutty, grassy or fruity notes.

These fatty acids can also interact with other components in the cheese to form esters, aldehydes and alcohols, which add depth to the aroma and flavour.

Impact of lipolysis on texture

Lipolysis also influences texture. In some cheeses, it helps create a smooth, velvety mouthfeel, especially in bloomy rind cheeses like Brie or Camembert. In others, such as Manchego or Pecorino, it contributes to a crumbly, almost dry texture.

The role of microbes in cheese maturation

Microbes, including bacteria, moulds and yeasts, play a critical role in affinage. While cheesemakers add specific bacterial cultures during production, natural microorganisms present in the environment also influence the maturation process, especially in traditional cheesemaking.

Lactic acid bacteria

Lactic acid bacteria (LAB) are essential during the early stages of maturation, as they convert lactose into lactic acid, lowering the pH of the cheese. This acidic environment inhibits the growth of harmful bacteria and sets the stage for the ageing process. Over time, LAB also contribute to proteolysis and lipolysis, producing compounds such as diacetyl, which gives the cheese a buttery aroma.

Moulds and surface-ripened cheeses

Moulds, such as Penicillium roqueforti in blue cheeses and Penicillium camemberti in bloomy rind cheeses, significantly influence texture and flavour. In blue cheeses, mould penetrates the interior, breaking down fats and proteins to create robust spicy flavours. In bloomy rind cheeses like Camembert, mould grows on the surface, softening the interior as enzymes diffuse into the cheese, creating a creamy texture.

Brevibacterium aurantiacum

In washed rind cheeses (such as Limburger or Époisses), Brevibacterium aurantiacum are responsible for the characteristic orange, sticky rind and strong, pungent smell. This bacterium breaks down proteins and fats, contributing to the bold, meaty flavours that develop over time.

Time and environmental factors in maturation

While microbial activity and enzymatic breakdown are the primary biochemical processes behind cheese maturation, the environment in which cheese ages is equally important. Temperature, humidity and airflow in ageing rooms or caves significantly impact the final product.

Temperature

Cheese is typically aged at temperatures between 10-15°C (50-60°F). Higher temperatures accelerate microbial activity and enzymatic reactions, leading to faster maturation, but may result in unwanted flavours or textures.

On the other hand, cooler temperatures slow the process, allowing for more gradual flavour development. This is particularly desirable for cheeses that mature for extended periods, such as Parmigiano Reggiano, which can age for 24-36 months or more.

Humidity

Humidity levels in the ageing environment regulate the cheese’s moisture content. Lower humidity helps form a firm rind in hard cheeses like Gruyère or Comté, which protects the cheese during long maturation periods. Softer cheeses, such as Brie or blue cheeses, require higher humidity to encourage mould growth and rind development.

Airflow

Finally, air circulation is crucial for surface-ripened cheeses. Proper airflow ensures even microbial growth on the cheese surface, while preventing excess moisture that could lead to spoilage.

Why some cheeses mature longer than others

Not all cheeses are suited to long maturation periods, mainly due to their moisture content and microbial composition. Cheeses with higher moisture levels, such as Brie or Mozzarella, are more susceptible to spoilage and typically have shorter ageing times.

In contrast, hard cheeses with low moisture, such as Sbrinz or Cantal, are ideal for long-term maturation.

Long-aged cheeses develop deeper, more concentrated flavours, while softer, shorter-aged cheeses retain a milder, fresher taste. Cheddar, for example, can be aged for just a few months (mild Cheddar) or several years (Extra Mature Cheddar), with flavour intensity increasing over time as more proteins and fats break down.

Conclusion

As you can see, the science behind cheese maturation is a fascinating blend of biochemistry, microbiology and environmental control. Over time, the breakdown of proteins and fats through proteolysis and lipolysis, along with microbial activity, gives rise to the rich flavours and unique textures of aged cheese.

Through careful management of these processes, cheesemakers are able to craft a diverse array of cheeses, each with its own distinct character.

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

The post Science Behind Cheese Maturation (How Affinage Crafts Cheese) appeared first on Cheese Scientist.

Let’s talk holes.

Big ones. Small ones. Neat little rounds. Occasional chaotic craters that look like something went very wrong in the ageing room.

Because holes in cheese aren’t decorative. They’re not air bubbles. And they’re definitely not there “to make the cheese lighter”.

They’re biology under pressure.

Cheeses like Swiss-style cheeses, Emmentaler, and some styles of Gouda don’t just have holes. They create them, slowly and deliberately, as part of fermentation.

Once you understand why, you stop seeing holes as quirks and start seeing them as evidence.

Evidence that microbes did exactly what they were supposed to do.

First things first: those holes have a name

Cheesemakers don’t call them holes. They call them eyes.

And that’s important, because eyes aren’t random voids. They’re a specific structural feature caused by gas formation inside the cheese during ripening.

Whether a cheese has eyes, tiny pinholes, cracks, or no openings at all depends on a surprisingly precise balance of factors:

• Which bacteria are present
• How much lactic acid is available
• How elastic the curd structure is
• Temperature during ageing
• Time

Change one variable and the entire outcome shifts.

That’s why two cheeses made from the same milk, on the same day, can age very differently.

The short explanation: gas made the holes

At its simplest, eye formation comes down to one thing.

Gas.

Certain bacteria inside the cheese produce carbon dioxide as part of fermentation. That gas builds up inside the cheese paste. If the paste is flexible enough, it stretches and forms bubbles.

Those bubbles become eyes.

If the paste is too rigid, the gas escapes. Or worse, it tears the cheese apart.

So when you see beautiful, round eyes, you’re looking at a cheese where fermentation, structure, and timing lined up perfectly.

The real hero: propionic acid bacteria

Most cheeses start with lactic acid bacteria. They convert lactose into lactic acid and drop the pH. That’s step one.

Eye-forming cheeses have a second act.

Enter Propionibacterium freudenreichii.

This bacterium consumes lactic acid and converts it into:

• Propionic acid
• Acetic acid
• Carbon dioxide

The carbon dioxide forms the eyes. The propionic acid creates the nutty, sweet aroma we associate with Swiss-style cheeses.

No propionic bacteria, no eyes. It’s that simple.

This is why eye formation happens after pressing, after initial fermentation, and often weeks into ageing.

Why Emmentaler has those iconic giant holes

Emmentaler didn’t become the visual shorthand for “cheese” by accident. Its eyes are large, glossy, and evenly distributed. That’s not luck. It’s engineering.

Raw milk plays a role

Traditional Emmentaler is made from raw milk. Raw milk carries a richer microbial ecosystem, including components that support propionic fermentation later on.

Pasteurised versions can still form eyes, but they tend to be smaller and more uniform.

The curd is designed to stretch

Emmentaler curds are cooked at relatively high temperatures and stirred extensively. This expels whey and creates a smooth, elastic protein network.

Think balloon, not brittle shell.

When gas builds up, the curd stretches instead of cracking.

Warm ageing is essential

After pressing, wheels are moved into warm cellars, typically around 20–24°C.

This warmth activates propionic bacteria. Carbon dioxide production increases. Eyes slowly expand from the inside.

Too cold, and nothing happens. Too warm, and the cheese risks splitting.

Time finishes the job

Eye formation isn’t immediate. It takes weeks. Sometimes months.

Cut an Emmentaler wheel too early and the eyes will be small or incomplete. The cheese simply hasn’t finished inflating yet.

Swiss cheese isn’t a single cheese

“Swiss cheese” is a style, not a protected name.

In Europe, it covers multiple Alpine cheeses. Outside Europe, it usually refers to a mild, industrial Emmental-style product.

The science is the same. The execution differs.

Industrial Swiss-style cheeses often use:

• Highly standardised starter cultures
• Shorter ageing periods
• More controlled textures

The result is smaller, more predictable eyes and a milder flavour.

Still cheese. Just less dramatic.

A quick note on Jarlsberg and its holes

Jarlsberg is often grouped with Swiss-style cheeses, but it’s a much more deliberately engineered example of eye formation.

Developed in Norway in the mid-20th century, Jarlsberg uses propionic acid bacteria to produce carbon dioxide during ripening, just like Emmentaler. That gas creates the holes and contributes to the cheese’s mild, slightly sweet flavour.

The difference is control.

Jarlsberg is typically made from pasteurised milk with tightly managed starter cultures and ageing conditions. This leads to smaller, more uniform eyes and far fewer structural surprises.

Same biology. Less chaos.

Why Gouda sometimes has holes and sometimes doesn’t

Gouda is where things get interesting. Some Gouda wheels have small, tidy eyes. Others are completely closed. Both can be correct.

That’s because Gouda sits right on the edge of eye-forming conditions.

Washed curds change the chemistry

Gouda is made using a washed-curd process. Whey is removed and replaced with warm water. This reduces lactose levels in the curd. Less lactose means less lactic acid later on.

And less lactic acid means less fuel for propionic bacteria.

Propionic bacteria are optional

Some Gouda styles include them. Some don’t.

Even when they are present, the environment isn’t ideal for large gas production.

The result is usually:

• Small eyes
• Irregular openings
• Or no eyes at all

Young Gouda may show eyes. Aged Gouda almost never does.

Same cheese family. Very different outcomes.

Why many cheeses never form holes

If gas causes holes, why don’t all cheeses end up full of them?

Because many cheeses are built to prevent it.

Dense curd structures

Cheeses like Cheddar or Parmigiano Reggiano are pressed firmly and expel more moisture.

The structure doesn’t stretch. Gas either escapes or stays dissolved.

Different microbial pathways

If propionic bacteria aren’t present, no carbon dioxide is produced at that stage.

Plenty of cheeses rely solely on lactic fermentation.

Cold ageing environments

Low temperatures slow bacterial metabolism. Less activity. Less gas. Fewer eyes.

Eye-forming cheeses require a deliberate warm phase. Without it, nothing happens.

When eye formation goes wrong

Eyes should be round, smooth, and evenly distributed. When they’re not, it usually means something went off script.

Cracks and slits

Long, jagged openings suggest gas formed too quickly or the curd wasn’t elastic enough.

Often caused by:

• Excessive fermentation
• Poor curd knitting
• Temperature fluctuations

Late blowing defects

This is a serious fault.

Certain unwanted bacteria, like Clostridium species, can ferment residual sugars late in ageing, producing gas when the cheese can no longer stretch.

The result is splitting, off-flavours, and structural failure.

No eyes at all

Sometimes propionic bacteria simply don’t activate. This can happen if the cheese is too acidic, the cellar is too cold, or the microbial balance is off.

You still get cheese. Just not the one you planned.

The persistent myth: “holes come from trapped air”

They don’t.

Air pockets from pressing would be irregular, shallow, and inconsistent. True eyes are smooth, spherical, and distributed throughout the paste.

They form slowly, after pressing, from gas produced in place. Cheese doesn’t trap air. It ferments itself open.

The recent claim: is hay responsible for cheese holes?

Over the past few years, a headline has made the rounds claiming that hay particles, not bacteria, are responsible for holes in Swiss-style cheeses.

The story usually goes like this: microscopic hay dust from traditional barns introduces particles that act as nucleation points for gas bubbles, helping eyes form.

There is some truth here. And a lot of misunderstanding.

What the research actually showed

Studies from Swiss researchers found that modern, ultra-clean milking systems reduced the number of natural particles in milk.

Fewer particles meant fewer places for gas bubbles to start forming.

When tiny particles from hay dust were reintroduced, eye formation became more predictable.

So yes, particles can influence where eyes start.

What hay does not do

Hay does not produce gas. It does not replace bacteria. It does not create eyes on its own.

Without propionic bacteria producing carbon dioxide, nothing happens.

Hay particles are scaffolding, not engines.

Why the claim got exaggerated

“Holes caused by bacteria” isn’t a catchy headline.

“Holes caused by hay” is.

But stripping the context makes it sound like centuries of cheese science were wrong, which simply isn’t true.

Eyes still come from fermentation. Hay just helps guide bubble formation in traditional systems.

It’s a nuance, not a revolution.

Eyes influence flavour, not just appearance

Those holes aren’t neutral.

Gas formation affects moisture distribution, texture, and aroma development.

Eye-forming cheeses tend to have:

• Sweeter notes
• Nutty aromas
• Softer textures around the eyes

That’s propionic acid doing its work.

Remove the eyes and you remove part of the cheese’s identity.

Why holes became iconic

In Alpine cheesemaking, well-formed eyes were proof of skill. They showed the cheesemaker understood milk, microbes, and time.

Even today, eye quality is used in grading traditional Swiss-style cheeses.

They’re not decoration.

They’re evidence.

So why do some cheeses have holes?

Because:

• The right bacteria were present
• The curd could stretch
• Temperature allowed gas production
• Time did the rest

Swiss-style cheeses, Emmentaler, and some Gouda are built to make space for fermentation.

Others are built to resist it.

Neither approach is better. They’re just telling different microbial stories.

Final thought

The next time you see holes in cheese, don’t think “Swiss”.

Think controlled fermentation. Think bacteria inflating protein networks from the inside out. And think centuries of cheesemakers learning how to let gas exist without letting chaos take over.

Cheese doesn’t get holes by accident.

It earns them.

Want more cheese science like this?

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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. 

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The post Why Some Cheeses Have Holes: The Real Science Behind Swiss, Emmentaler & Gouda appeared first on Cheese Scientist.

SEE ALSO: Do you know your double creams from your triple creams? →

What is ripening?

This is an incredibly complex process and it would take a dissertation to attempt to explain all of it. Therefore, let’s focus on one particular component today, proteolysis. And how it contributes to the soft texture of white mould cheeses like Brie and Camembert. 

A sliding scale of textures

Picture this. You’ve just cut through this gorgeous Camembert that you bought from your monger. And you notice a range of textures through the cross-section. The centre is still quite light in colour and firm (we’ll call this chalky).

On the other hand, the bit just under the surface is more yellow and soft (we’ll call this oozy). Why does it look like this?

Cheese is a network of proteins

Basically, cheese is a network of a specific type of protein called casein. And proteolysis is the process by which said proteins are broken down.

Quick linguistic detour: Lysis is actually derived from the Greek work lýsis which means “loosening”. Hence, proteolysis is the loosening of proteins. 

What causes proteolysis in cheese?

Before we talk about how proteolysis affects texture and colour of cheese, let’s take a brief look at why it happens.

Actually, enzymes called proteases are the main cause of proteolysis in cheese. They can come from coagulants like rennet (see link in bio to read more about rennet), starter culture bacteria and surface mould. 

Penicillium camemberti

In the case of Camembert, the mould on the surface (Penicillium camemberti) produces proteases that break down the protein and produce ammonia.

Unsurprisingly, this process begins with the part of the cheese that is directly underneath the rind. Eventually, it slowly spreads towards the centre.

Why is the colour different?

As the protein breaks down, the cheese’s texture loosens. Consequently, this causes the cheese to become more oozy. But why is the colour slightly different to the chalky centre?

Ammonia, I’m talking to you! Effectively, the ammonia that is formed when the protein breaks down makes the cheese less acidic near the surface. This further impacts how the proteins stick together. As a result, the cheese looks slightly translucent with a tinge of yellow.  

Ripening from the surface to the centre

During maturation, the cheese softens first near the rind, but the centre still has a strong casein structure and is, hence, more chalky. 

If you let your Camembert ripen for long enough, the entire structure will eventually break down to become completely oozy. Unfortunately, this also leads to higher ammonia levels which may create an unpleasant smell. 

The process by which the centre goes from chalky to oozy is a fairly complex one and involves the cheese’s acidity and calcium levels. And that would be a separate blog post in its own right.

Now you know that happens to soft cheese at it ripens

So, there you have it. This is what happens to soft cheese as it ripens. 

Now, tell me… Do you like your soft cheeses with a chalky centre? Or do you prefer them oozy throughout? Drop us a comment below.

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

The post What Happens To Soft Cheese As It Ripens? appeared first on Cheese Scientist.

SEE ALSO: Why are some cheeses so orange? →

The types of cheese crystals

Those crunchy bits in cheese are called cheese crystals. Pretty fancy name right? Moreover, you are most likely to find them in semi-hard to hard cheeses, that have been aged for an extended period of time.

Effectively, those crystals that fall largely under two categories, tyrosine and calcium lactate crystals. 

Tyrosine crystals

What is tyrosine?

Tyrosine is a non-essential amino acid that is formed in cheese by a very specific cheese culture called Lactobacillus helveticus.

Interestingly, this lactic acid producing bacterium derives its name from the Latin name for Switzerland, Helvetia.

Where to find tyrosine crystals

Unsurprisingly, the crystals most commonly found in many aged Swiss, Italian and Dutch cheeses are tyrosine. Examples include Gruyère, Parmigiano Reggiano and Beemster.

Moreover, cheesemakers add Lactobacillus helveticus cultures to milk to encourage flavour formation. What it actually does on a molecular level is break down the protein in the milk to form a number of amino acids, including tyrosine.

How tyrosine crystals are formed

As the tyrosine content in cheese builds up over time, it starts to crystallise out and clump together. This process can happen both on the surface of cut cheeses and within the eyes of some semi-hard cheeses.

Do tyrosine crystals have any flavour?

Whilst tyrosine makes a significant contribution to the texture of cheese, it is actually flavourless. Paradoxically, tyrosine crystals are often referred to as flavour crystals in cheese.

The main reason for that might be because of its presence on cheeses that have been matured for an extended period of time. As a result of the age, those cheeses tend to have a more pronounced flavour that can be incorrectly attributed to the crystals.

Calcium lactate crystals

What is calcium lactate?

Now that we’ve covered tyrosine, let’s discuss the second most common crystal, calcium lactate.

Calcium lactate is a white, fine crystalline salt that is sometimes used as a food additive. 

How is calcium lactate formed in cheese?

In cheese, calcium lactate results from the reaction between lactic acid and calcium salts from the milk. As the cheese matures, the culture breaks down the lactose in milk to produce lactic acid.

Over time, the amount of lactic acid in cheese increases significantly. As those levels rise, they start to bind to calcium ions to form calcium lactate.

Where to find calcium lactate

Similarly to tyrosine, calcium lactate starts to crystallise and appear as white layers on the surface of the cheese. Because the crystals need moisture to form, they are more likely to appear on the outside of cheese.

What does calcium lactate look like?

Unlike tyrosine, calcium lactate crystals tend to form a powdery smear across the surface of hard cheeses such as Cheddar and Gouda. As a result of this, they don’t usually have the crunchy texture that tyrosine has.

However, one similarity between the two is that they are completely flavourless, and of course, safe to eat.

You love those crunchy bits in cheese right?

To summarise, the crunchy texture in aged cheeses is mostly due to the presence of two crystals, tyrosine and calcium lactate. Having said that, there are also some other amino acids such as leucine that can be present in certain cheeses.

So there you have it! Now you know what those crunchy bits in your favourite hard cheese actually are. What’s your favourite crunchy cheese? Drop us a comment below.

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

The post Cheese Crystals: What Are Those Crunchy Bits? appeared first on Cheese Scientist.

Mould is cheese

Mould can be scary if you’re not used to seeing it on food. But it can actually be an important part of cheesemaking. If you’ve ever wondered whether you can eat mouldy cheese, we’ve got all the answers to your questions below.

If you’ve eaten cheese even once in your life (I know you have, you wouldn’t be here otherwise), then you have eaten mould. Are soft cheeses your jam? Meet Penicillium candidum. Are you more of a blue cheese fiend, say hello to our little friend, Penicillium roqueforti. 

What moulds are safe to eat?

Picture this. You bought yourself a little treat the last time you were at your local cheese shop. A round of your favourite triple cream soft cheese, Brillat-Savarin. Today is the day when you get to dig into it! You’ve been waiting for this moment since you brought it home. You go to the fridge and pull it out.

Oh no, there is a patch of fuzzy mouldy growth on top of the rind! What do you do? Do not freak out! Read on to find out why this mould is perfectly safe to eat. Moreover, mould can be desirable in cheese.

Mould in cheesemaking

Mould is used for various reasons in the cheesemaking process. Some like Penicillium candidum and Geotrichum candidum add the beautiful white textures that we all love on the rind. Others like Penicillium roqueforti and Penicillium glaucum add the blue veins that we all go gaga over in blue cheeses. 

Cheese is a living organism

In summary, mould contributes significantly to the aroma, flavour and texture of the cheeses we love. Furthermore, think of both the mould and the cheese as living organisms.

When you keep cheese in your fridge, it breathes and lives and continues to grow. So does the good mould. So, it is not uncommon to find fluffy bunny tails growing on the surface of soft white mould cheeses. Or patches of blue on some hard cheeses. One great example of the latter is a gorgeous Cheddar from Wales called Hafod. 

What types of mould aren’t safe to eat?

However, there are some moulds that can be dangerous. The most common one is Aspergillus niger, a.k.a the Black Mould. This fungus will have a severe negative impact on the food product it contaminates and releases toxins in the body that can be harmful. Having said that, it is very rarely found on cheese.

Moreover, some other moulds can be a bit like an iceberg. You will only see a flat patch of greyish-blue or green on the surface of the cheese. The rest will lie under the rind.

Can mouldy cheese be eaten?

Also, remember that your fridge may not be a controlled environment and you do not really know what moulds are present. Therefore, we need some rules. The safest approach is to avoid eating any questionable mould. What you do with the rest of the cheese will depend on its moisture content and texture.

Cheeses you should discard

If it is fresh cheese (e.g. Ricotta, Queso Fresco, Cream Cheese) or pasta filata (e.g. Mozzarella, Stracciatella, Bocconcini), the best thing is to discard all of it. Those cheeses are high in moisture and quite soft. Because of this, the mould will have very likely penetrated all the way through. 

Cheeses you can save

On a more positive note, if it is a semi-hard (e.g. Comté, Gruyère, Emmentaler) to hard cheese (e.g. Cheddar, Gouda, Parmigiano Reggiano), the mould will most probably be only on the surface and can be sliced off. The rest of the cheese should be absolutely fine to eat. 

One last piece of advice

Do not leave cheese long enough in your fridge for it to develop contamination! Buy what you will eat within a week. One exception to this rule is if you are buying a whole wheel of cheese with a natural rind. Those will actually get better with time as you allow them to reach their “Best Before Date”.  

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

The post Can You Eat Mouldy Cheese? appeared first on Cheese Scientist.

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

The post Why Some Cheeses Are Covered in Ash (And What It Actually Does to the Cheese) appeared first on Cheese Scientist.