From Brie to Parmigiano Reggiano, the sheer variety of cheeses is rooted in the complex science behind their production. Central to this is the process of maturation, also known as affinage, during which cheese develops its characteristic flavours and textures.
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:
- Fresh cheeses (e.g., Ricotta, Cottage Cheese) are not aged or are aged only for a few days.
- 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:
- Glutamic acid 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 is a a hipster, eco-warrior and slow food afficionado. Coming from a scientific background, Jonah has a particular interest in cheese science. And yes, he loves a good cheese pun!
