Why Does Cheese Smell Strong When Stored?

The Biochemistry of Aroma: Why Cheese Develops Potent Smells During Storage

At the microscopic level, a block of cheese is a thriving, albeit slow-moving, ecosystem. When you store cheese, you are essentially providing a controlled environment for the continued metabolic activity of microorganisms like bacteria, yeasts, and molds. The primary drivers behind those pungent aromas are two biochemical processes: proteolysis (the breakdown of proteins) and lipolysis (the breakdown of fats). Enzymes such as proteases and lipases, either naturally present in the milk or introduced by cheesemakers, act like molecular scissors. They snip long-chain casein proteins into smaller amino acids and peptides, and triglycerides into free fatty acids. This is where the magic—or the stench—begins.

Consider the role of sulfur. Amino acids like methionine and cysteine contain sulfur atoms. As these are further metabolized by bacteria—specifically during the ripening of washed-rind cheeses—they release volatile sulfur compounds such as methanethiol, dimethyl sulfide, and hydrogen sulfide. These compounds are detectable by the human nose at incredibly low concentrations, often in the parts-per-billion range. This is why a tiny piece of Limburger can permeate an entire refrigerator. Simultaneously, lipolysis generates free fatty acids that are subsequently converted into methyl ketones, alcohols, and esters. In blue-veined cheeses, the mold Penicillium roqueforti is a master of this craft, producing 2-heptanone and 2-nonanone, which provide that signature sharp, piquancy. Research published in the Journal of Agricultural and Food Chemistry highlights that the complexity of these volatile profiles is highly dependent on the 'microbial succession'—the order in which different microbes dominate the cheese surface.

Environmental factors act as the accelerator for this biochemical engine. When you store cheese in an airtight plastic container or wrap, you are creating a micro-atmosphere. Volatile organic compounds (VOCs) that would otherwise dissipate into the air are trapped, effectively 'marinating' the cheese in its own aroma. Furthermore, temperature is the ultimate regulator of enzymatic speed. According to the Arrhenius equation, microbial metabolism generally doubles for every 10°C increase in temperature. This is why a cheese left at room temperature for a few hours will develop a significantly more aggressive odor profile than one kept at a stable 4°C. The moisture content of the cheese also plays a pivotal role; high-moisture cheeses provide a more fluid medium for these enzymes to travel and interact with substrates, leading to faster flavor and aroma development compared to hard, dry cheeses like aged Parmesan.

Managing Your Cheese: How Storage Affects Flavor and Safety

To manage the aromatic intensity of your cheese, you must balance the need for 'breathing' with the need to prevent drying out. Most experts recommend wrapping cheese in breathable materials, such as wax paper or specialized cheese paper, rather than tight plastic wrap. Plastic creates a suffocating environment that can lead to off-flavors, as it traps moisture and promotes the growth of anaerobic bacteria, which can turn a delicious aroma into a sour, ammonia-like stench. If you have a particularly pungent cheese, store it in a dedicated vegetable drawer or a sealed container with a small amount of airflow to prevent the scent from migrating to your butter or milk. Always remember that cheese is a living product; it will continue to evolve as long as it is in your fridge. If you notice a sudden, sharp ammonia smell, it is a sign that the pH balance has shifted, often due to improper storage temperature, and it is time to consume or discard it. For the best experience, bring your cheese to room temperature 30 minutes before serving, as this allows those complex volatile compounds to volatilize properly and hit your palate with full force.

Why It Matters

The science of cheese aroma is more than just a culinary curiosity; it is a vital component of food security and economic health. By understanding the volatile compounds that signal proper aging versus spoilage, consumers can drastically reduce food waste. Every year, millions of pounds of perfectly edible, high-quality cheese are discarded simply because consumers mistake the natural, pungent aroma of a rind for rot. Furthermore, this field of study underpins the global artisanal cheese industry. For small-scale producers, mastering the microbial succession is the difference between a world-class product and a failed batch. As we move toward more sustainable food systems, the ability to control and predict these chemical transformations allows for better shelf-life management and more efficient distribution, ensuring that traditional, nutrient-dense foods remain a viable part of our modern diet while minimizing the environmental impact of waste.

Common Misconceptions

A pervasive myth is that a strong-smelling cheese is necessarily 'bad' or unsafe. In reality, the most pungent cheeses—such as Epoisses or Taleggio—are intentionally crafted to be odoriferous. The smell is a hallmark of quality, not a sign of decay. Another common misconception is that the smell comes exclusively from the interior of the cheese. In many cases, the most intense aromas are concentrated on the rind, which is home to a dense colony of 'smear-ripening' bacteria like Brevibacterium linens. If you find a cheese too aggressive, simply trimming the rind can significantly alter the eating experience. Finally, many believe that all blue cheeses are fundamentally the same. While they share the Penicillium mold, the specific strain of mold, the milk source (cow, goat, or sheep), and the aging duration create vastly different aromatic profiles—ranging from the spicy, metallic notes of Gorgonzola to the creamy, earthy sweetness of a mild Danish Blue. Understanding these nuances turns a simple grocery store trip into a sensory exploration.

Fun Facts

• The human nose can detect certain sulfur compounds found in cheese at concentrations as low as one part per billion.
• Brevibacterium linens, the bacteria responsible for the 'stinky' smell of many washed-rind cheeses, is also a primary contributor to human foot odor.
• The 'eyes' in Swiss cheese are actually carbon dioxide bubbles trapped during the fermentation process, which also influences the development of volatile aromatic compounds.
• Some researchers are using 'electronic noses'—sensors capable of detecting specific VOCs—to monitor the ripening status of cheeses in real-time.

Related Questions

• Why does some cheese smell like ammonia?
• How does the type of milk affect the final aroma of a cheese?
• What is the best way to store cheese to keep it fresh longer?
• Why do some cheeses have a 'rind' and others do not?