Say you’re at a local market, and in the corner of your eye, you catch sight of a cheese display. Aged hard cheeses, soft varieties, even some cheese from the village of Cheddar, it’s all there. You’re a true cheese lover, so you grab a few of your favorites and take them home, dreaming of the complex flavors they’ll bring to your next meal.

But then, as you unpack your haul, you notice something on the surface of the cheeses—white specks, tiny white spots, even some crystalline structures. Is it mold? Cheese crystals? You panic. Should you throw the cheeses out? Is it safe? Can you still relish the nutty flavor of your Parmigiano Reggiano or the creamy goodness of your cottage cheese?

Don’t fret! Today, we’re going to take a closer look at these tiny invaders, breaking down the significant difference between cheese crystals and mold. We’ll cover everything from the formation of calcium lactate crystals to the starter cultures involved in traditional cheese-making. We’ll discuss the aging process, mold growth, and even the role of lactic acid bacteria. By the end, you’ll be a bona fide expert, ready to impress your fellow cheese connoisseurs at the next gathering.

Let’s start our exploration, one delicious bite at a time.

What are Cheese Crystals?

Defining Cheese Crystals

Cheese crystals, those little white crystals you sometimes find in your aged cheeses, might initially be mistaken for mold, but they’re a completely different entity. In reality, they’re a cheese lover’s delight and a sign of a well-aged cheese.

During the aging process, cheeses undergo protein breakdowns, transforming their flavor and texture. These breakdowns release free amino acids into the paste of the cheese—the soft, creamy part inside the rind. As the cheese ages, some of these free amino acids can clump together, forming tyrosine crystals. In addition, the process can also lead to the formation of calcium lactate crystals as lactic acid levels rise and react with calcium ions present in the cheese.

These crystals can appear both on the exterior of the cheese and within the interior of the cheese, providing a pleasant crunch when you bite into your aged Cheddar or hard Swiss. If you take a closer look, you’ll find they often have a white or slightly yellowish color and are typically small in size.

Types of Cheese Crystals

There are primarily two types of cheese crystals: Tyrosine and Calcium lactate.

age cheese with tyrosine crystals

Tyrosine crystals are often seen in high-protein cheeses like Parmesan, aged Gouda, or aged Cheddar. They usually appear as small, white or slightly yellowish, round, hard dots, often giving the cheese a sandy or gritty texture. They are commonly found both on the interior and the exterior of the cheese.

cheese with calcium lactate crystals

Calcium lactate crystals, on the other hand, are more often found in aged cheddar cheeses and are typically a result of long aging times combined with high temperatures during cheese making. They are typically larger and have a more crystalline, almost glassy appearance compared to tyrosine crystals. They also appear whiter and can often be found on the exterior of the cheese as well as the interior.

However, it’s worth noting that the appearance can vary depending on many factors like the type and age of the cheese, so these descriptions are not universally applicable. Food scientists or cheese experts often have to use microscopy or other analysis methods to definitively identify the type of crystals in a cheese.

What is Mold on Cheese?

Understanding Mold on Cheese

mold through a magnefying glas

Mold on cheese – it’s that uninvited mold growth, often appearing as blue, green, or even white stuff on the surface of your cheeses, that might cause you to second-guess your anticipated cheese feast. Unlike cheese crystals, which are a result of the aging process, mold on cheese is typically an indicator of spoilage or, in some cases, a critical part of the cheese-making process.

mold magnified on microscope

Mold is a type of fungus that grows in thread-like structures known as hyphae. It thrives in environments with high moisture and moderate temperatures, making cheese a potentially ideal home. In fact, when you see mold on the surface of cheeses, it’s usually due to exposure to mold spores present in the environment. Not all mold is harmful, but some types can cause food poisoning, which is why it’s essential to know the difference between intended mold in cheese and the uninvited kind.

Different Types of Mold

Mold comes in all shapes and sizes, from the blue veins running through your favorite Roquefort to the white rind on your Camembert. In fact, many cheese connoisseurs will tell you that mold is a good thing and can contribute to a cheese’s complex flavor.

For example, the Penicillium roqueforti and Penicillium camemberti molds are crucial in the development of blue and soft cheeses, respectively. They’re intentionally introduced during the cheese-making process, infusing the cheese with unique flavors and textures.

But then there’s the mold that makes its appearance well after the cheese has left the creamery – the green, fuzzy stuff that can ruin your mood and your appetite. This mold, whether it’s growing on the outside of the cheese or infiltrating the interior of the cheese, is generally unwanted and may pose a risk to your health.

In the next section, we’ll explore the significant difference between cheese crystals and mold and how to distinguish between them. So, the next time you pull out your beloved Beemster Premium Dutch cheese, you’ll know exactly what you’re looking at.

Cheese Crystals Vs. Mold: The Significant Difference

Cheese Crystals: An Expected Presence

By now, you know that cheese crystals are a natural byproduct of the aging process in certain types of cheeses. But what’s more important is that these crystals are not just okay to consume, they’re actually desirable. Cheese connoisseurs often consider the presence of crystals a mark of quality, signaling a well-aged cheese.

These white marks or dots on the cheese bring an unexpected and pleasant crunch to your cheese-eating experience, along with adding to the depth of flavor. They’re especially prevalent in hard cheeses like Parmigiano Reggiano and aged Gouda, where the lengthy aging process allows the protein chains to break down and form crystals.

Mold: An Uninvited Guest


Mold, in contrast, can be an uninvited guest. If you spot mold on cheeses that are not supposed to have them (like your cream cheese or fresh Mozzarella), that’s a sign the cheese has been contaminated and is starting to spoil. You’ll want to check the expiration date or the use-by date, as consuming spoiled cheese can potentially lead to food poisoning.

However, there are exceptions. Certain types of cheeses, like Blue cheese or Roquefort, intentionally introduce molds as part of their production process. In these cases, the mold contributes to the cheese’s unique flavor profile and is perfectly safe to eat.

In short, cheese crystals are typically a good thing and signify a high-quality, aged cheese, while mold can either be a good thing (as in the case of blue cheeses) or a bad thing (as in the case of mold growth on a cheese that’s not supposed to have it).

Next, we’ll delve into the fascinating science behind how cheese crystals develop during the aging process and the factors that can influence their formation. 

How Cheese Crystals Develop

The Science Behind Cheese Crystals

The formation of cheese crystals is a complex process deeply intertwined with the chemistry of cheese aging. During aging, the proteins and fats in cheese undergo enzymatic breakdown, which releases free amino acids and fatty acids into the cheese matrix.

Two primary types of crystals are formed during this process: tyrosine and calcium lactate. Tyrosine crystals are a result of protein breakdown. When proteins break down, they release a variety of amino acids, one of them being tyrosine. Over time, as the cheese ages, these free tyrosine molecules can clump together to form crystals.

Calcium lactate crystals, on the other hand, are a result of the reaction between lactic acid and calcium in the cheese. As the cheese ages, the level of lactic acid in the cheese gradually increases due to the ongoing fermentation. This lactic acid can react with calcium ions present in the cheese, leading to the formation of calcium lactate crystals.

So, the next time you enjoy a slice of your aged Cheddar cheese and experience that pleasant crunch, know that it’s the result of a fascinating journey of transformation and a testament to the art and science of cheese-making.

Factors Affecting Crystal Formation

While the formation of crystals is a natural part of the cheese aging process, it’s important to note that several factors can influence their development.

cow and a goat

The type of milk used to make the cheese plays a significant role. For instance, cheeses made from cow’s milk, which has a high calcium content, are more likely to develop calcium lactate crystals. On the other hand, cheeses made from goat or sheep milk, which have lower calcium levels but higher protein content, might be more inclined towards tyrosine crystal formation.

parmigiano reggiano cheese

The aging process itself also heavily influences crystal development. Longer aging allows for more protein breakdown and lactic acid production, leading to more crystal formation.

So, hard cheeses that are aged for a long time, like Parmigiano Reggiano or aged Gouda, often have a more pronounced crystal presence.

The storage conditions of the cheese can also affect the formation of crystals. Cheeses aged at high temperatures and low humidity are more likely to develop crystals due to increased rates of protein and fat breakdown and lactic acid production.

Now that you’re familiar with the science behind cheese crystals let’s explore the role of mold in cheese production and some cheese varieties that use mold intentionally to achieve unique flavors and textures. 

Mold in Cheese Production

The Role of Mold in Cheese-making

Despite the negative connotation that often comes with the word “mold,” in the world of cheese-making, certain molds play an integral role in crafting some of our most beloved cheeses. While unwanted mold on cheese can be a sign of spoilage, mold introduced intentionally during the cheese-making process contributes to flavor, texture, and the overall uniqueness of a cheese variety.

Molds are used in cheese-making for several reasons. They can contribute to the development of flavor, help to break down the cheese’s proteins and fats (a process known as proteolysis and lipolysis, respectively), and even play a role in shaping the cheese’s final texture.

In fact, the mold spores are introduced at specific points in the cheese-making process depending on the desired outcome. Some molds are mixed directly into the milk before curdling, some are added during curdling, and others are introduced after the cheese is formed, often by being sprayed on the cheese or added to the brine in which the cheese is soaked.

Cheese Varieties with Intentional Mold

Let’s take a closer look at some well-known cheese varieties that intentionally employ molds as part of their production process.

Penicillium roqueforti on a petri dish

Blue cheeses like Roquefort, Gorgonzola, and Stilton are known for their distinct blue or green veins. This marbling is the result of Penicillium roqueforti, a mold that’s added during the cheese-making process. The cheese is then aged in conditions that encourage the growth of the mold, resulting in its signature look and strong, tangy flavor.

 Penicillium camemberti on a petri dish

Brie and Camembert are examples of soft cheeses that feature a bloomy rind, thanks to the Penicillium camemberti mold. This mold is introduced onto the surface of the cheeses after they’re formed, creating a soft, edible rind and a unique, earthy flavor.

In contrast to the unsightly mold you might find on an old block of cheese in the back of your fridge, the molds used in cheese-making are carefully selected and controlled. They contribute to the diversity of flavors, textures, and appearances that make the world of cheese so varied and exciting.

But, to keep your cheese at its best, it’s essential to know how to store it correctly to avoid unwanted mold growth. So, let’s discuss some tips for storing cheese in the next section.

Wrapping It Up

From the distinct crunch of flavor crystals to the mold that can give cheeses like Blue or Camembert their unique taste, there’s a world of complexity within every cheese. As a cheese lover, it’s important to know these differences, so you can ensure the quality of your cheese and the safety of your eating experience.

Cheese crystals and mold, while both integral to the world of cheese, are vastly different. Cheese crystals are a result of the aging process, a natural occurrence that many cheese connoisseurs anticipate with delight. These crystals, whether they are tyrosine or calcium lactate, offer a pleasant crunch and complexity to aged cheeses. They’re a sign of well-aged cheese and perfectly safe – if not delicious – to consume.

Mold, on the other hand, can be both a friend and a foe. In controlled cheese-making environments, certain molds contribute to the cheese’s taste and aesthetic. However, unwanted mold growth in storage is a cause for concern. Recognizing the difference between these molds and understanding how to properly store cheese can help ensure your cheese stays fresh and safe to eat.

Understanding the nuances of cheese – from the aging process to the possible presence of crystals or mold – is a testament to its complexity and charm. The next time you enjoy a piece of cheese, you’ll have a deeper appreciation for what goes into its creation and the processes behind each bite.

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