The Cheese Fermentation Process: The Surprising Roles of Mold and Bacteria

Cheese, beloved around the world, owes its diverse flavors and textures to invisible tiny workers—molds and bacteria. In this article, we’ll scientifically explain the cheese fermentation process and examine in detail the characteristics of white-mold cheese, blue-mold cheese, and washed-rind cheese, as well as how microorganisms are involved in each.

What is Cheese? The Basics as a Fermented Food

Cheese is a fermented food made from milk (cow, sheep, or goat) with the help of microorganisms such as lactic acid bacteria, molds, and yeasts. Humans have been making cheese for thousands of years, and production methods vary greatly by region and culture. Today, there are over 1,000 types of cheese worldwide, each with its own unique flavor and character.

The basic cheese-making process involves coagulating milk to separate it into curd (solid portion) and whey (liquid portion), then aging the curd. During this aging process, various microorganisms work to give cheese its distinctive flavor and texture.

This fermentation mechanism, like the fermentation science of yogurt and fermentation science of kimchi, is driven by the activity of lactic acid bacteria and other microorganisms.

The Cheese Fermentation Process: 4 Steps

Cheese making proceeds in four major steps.

Step 1: Coagulation (The Work of Lactic Acid Bacteria)

First, a lactic acid bacteria starter is added to milk. The lactic acid bacteria break down lactose in the milk to produce lactic acid, lowering the pH and acidifying the milk. This acidification makes the casein protein in the milk easier to coagulate. Adding rennet (a coagulating enzyme) causes the milk to solidify and separate into curd and whey.

Step 2: Curd Formation and Shaping

The coagulated curd is cut and the whey is drained. The size of the curd pieces and the amount of whey removed determine the hardness and moisture content of the cheese. The curd is then packed into molds to shape it, and salt is added to season it. Salt not only provides flavor but also removes excess moisture and inhibits the growth of harmful microorganisms.

Step 3: Aging (The Appearance of Mold and Yeast)

This is the most important stage that determines the cheese’s character. The shaped cheese is aged in temperature- and humidity-controlled aging rooms for periods ranging from several weeks to several years. During this time, depending on the type of cheese, white mold, blue mold, bacteria, and other organisms work to break down proteins and fats, creating distinctive flavors.

Step 4: Completion

As aging progresses, complex chemical reactions occur inside the cheese, changing its flavor and texture. When the aging period is complete, the cheese is finished and ready for shipment.

White-Mold Cheese: Camembert and Brie

The quintessential white-mold cheeses are Camembert and Brie. The white, velvety layer covering the surface of these cheeses is formed by a white mold called Penicillium camemberti.

White mold is sprayed or applied to the cheese surface and multiplies in the high-humidity environment of the aging room. White mold secretes enzymes that break down proteins, gradually aging the cheese from the surface inward. In this process, the cheese’s texture becomes creamy and its flavor becomes mild yet increasingly complex.

Blue-Mold Cheese: The Secret of Blue Cheese

Blue-mold cheese, commonly known as blue cheese, is characterized by blue-green veins. These blue portions are formed by blue molds such as Penicillium roqueforti and Penicillium glaucum.

Unlike white-mold cheese, blue mold grows inside the cheese. During production, blue mold spores are mixed into the curd, and after shaping, the cheese is pierced with needles. Air enters through these holes, allowing the aerobic blue mold to proliferate inside and create the blue-green veins.

Because blue mold secretes many fat-breaking enzymes, blue cheese has a distinctive sharp flavor and strong aroma. Blue-mold cheeses beloved worldwide, such as Roquefort, Gorgonzola, and Stilton, are born from the work of this blue mold.

Washed-Rind Cheese: The Power of Bacteria

Washed-rind cheese is made by washing the cheese surface with brine, wine, brandy, or other liquids during aging. This washing encourages the growth of bacteria called Brevibacterium linens on the surface, forming an orange-colored rind.

These bacteria break down proteins to produce an intense aroma. Washed-rind cheeses such as Époisses, Pont-l’Évêque, and Munster are sometimes described as smelling “like feet,” but their taste is very creamy and mild.

Interestingly, Brevibacterium linens not only creates taste and aroma but also functions as a defense system for the cheese. The presence of these bacteria makes it harder for molds and unwanted microorganisms to proliferate, protecting the cheese.

The Collaborative Work of Lactic Acid Bacteria and Mold

In the cheese fermentation process, multiple microorganisms—lactic acid bacteria, molds, yeasts, and bacteria—work together. Lactic acid bacteria first acidify the milk, creating an environment where molds and bacteria can thrive. Then, molds and bacteria break down proteins and fats, giving the cheese its distinctive flavor.

This microbial interaction is what creates cheese diversity. Even using the same raw materials, different types of microorganisms and aging conditions produce completely different flavors of cheese.

How to Choose and Store Cheese

Choosing Cheese

When selecting cheese, pay attention to these points:

• White-mold cheese: The surface should be uniformly white and feel soft to the touch, indicating advanced aging.
• Blue-mold cheese: The blue mold should be evenly distributed, and the aroma shouldn’t be overpowering.
• Washed-rind cheese: The rind should be orange-colored and slightly moist, indicating freshness.

Storage Methods

Since cheese is a fermented food containing living microorganisms, proper storage is important:

• Refrigerate: Store at 5-10°C (41-50°F)
• Wrap: To prevent drying, wrap in cheese paper or wax paper
• Bring to room temperature before eating: To maximize flavor, remove from refrigerator 30 minutes before serving

Health Benefits of Cheese

Cheese offers health benefits characteristic of fermented foods:

• Rich in protein: Supports muscle and bone health
• Rich in calcium: Effective for preventing osteoporosis
• B vitamins: Support energy metabolism
• Lactic acid bacteria: Improve gut health

These health benefits, like those of natto’s remarkable health benefits and different types of miso, are a major attraction of fermented foods.

Conclusion

The cheese fermentation process is sustained by the collaborative work of various microorganisms: lactic acid bacteria, white mold, blue mold, and bacteria. These microorganisms break down proteins and fats, giving cheese its distinctive flavor, aroma, and texture.

The elegant white mold of Camembert, the bold blue mold of blue cheese, the distinctive bacteria of washed-rind cheese—each microorganism brings infinite diversity to the world of cheese.

Next time you savor cheese, remember the tiny microorganisms working behind the scenes. You’ll surely find the cheese tastes even richer.