Brie tastes like ammonia because it literally contains ammonia. The white mold on the rind breaks down proteins in the cheese into amino acids, and those amino acids further break down into ammonia as a natural byproduct. Every wheel of Brie produces some ammonia during ripening, but how much you taste depends on the cheese’s age, how it was stored, and whether it had a chance to breathe before you ate it.
How the Rind Produces Ammonia
The fuzzy white coating on Brie isn’t decorative. It’s a living colony of mold that actively digests the cheese from the outside in. As the mold grows, it breaks down casein (the main protein in milk) through a process called proteolysis: first into smaller protein fragments, then into individual amino acids. Those amino acids then get broken down further, releasing ammonia as a byproduct. This amino acid catabolism is actually one of the primary reactions that creates flavor in surface-ripened cheeses.
The mold also consumes lactic acid on the cheese’s surface, which raises the pH and makes the environment more alkaline. That alkaline shift is partly driven by the ammonia itself. As the surface becomes less acidic, calcium migrates outward, proteins in the interior begin to dissolve, and the paste softens from the edges toward the center. This is why a ripe Brie gets progressively gooey under the rind. The same chemistry that gives Brie its creamy, oozing texture is the chemistry that produces ammonia.
Why Some Wheels Are Worse Than Others
A faint whiff of ammonia is normal in any ripe Brie. The problem is when that faint whiff becomes the dominant flavor. Several things push it over that line.
Age is the biggest factor. The mold starts producing detectable ammonia within the first week of ripening, and production continues as long as the mold has protein to consume. By the time a wheel has been ripening for several weeks, ammonia levels in the paste can be significant. A Brie that sat too long in the supply chain, whether at the distributor, the store, or your fridge, will taste sharper and more pungent than one eaten closer to its prime.
Thickness matters too. Wheels thicker than about an inch tend to be overripe at the edges while the center is still chalky and underripe. The outer portion, closest to the mold, accumulates the most ammonia, so a thick wheel can taste aggressively ammoniated around the perimeter even when the middle hasn’t fully softened. Look for thinner wheels where the ripening is more even throughout.
Plastic Wrap Makes It Much Worse
Brie is a living, breathing cheese, and wrapping it tightly in plastic film is one of the fastest ways to ruin it. The mold and surface bacteria continuously release ammonia gas, which is volatile and would normally drift away. Plastic creates a sealed environment where that gas has nowhere to go. It builds up in the space between the wrap and the rind, gets reabsorbed into the paste, and concentrates to levels far beyond what you’d taste in a properly stored wheel.
Testing on Camembert (Brie’s close cousin, with the same mold) showed that ammonia in the headspace of plastic-wrapped cheese reached 142 parts per million after just 72 hours. The threshold where humans can detect ammonia by smell is around 12 ppm. That’s roughly twelve times the detectable level, which explains why unwrapping a plastic-sealed Brie can hit you with an eye-watering blast. Cheese shops typically wrap Brie in wax paper or specialty cheese paper that allows moisture and gas to pass through. If your Brie came from a supermarket sealed in plastic, the packaging itself may be a bigger problem than the cheese.
How to Tell If It’s Normal or Too Far Gone
A ripe Brie in good condition has a white rind that looks plump, as though the paste inside is gently pressing outward. The smell should be mushroomy and earthy, possibly with a slight sharpness that fades quickly. A mild ammonia note that disappears after a few seconds of open air is perfectly normal.
An overripe Brie looks different. The rind turns brownish and feels gummy or sticky rather than velvety. The interior may be excessively runny, almost liquid, and the ammonia smell lingers rather than fading. If the cheese smells strongly of ammonia even after sitting out unwrapped for 30 minutes, it’s past its prime. It won’t make you sick, but the flavor will be unpleasant and dominated by that chemical sharpness rather than the buttery, nutty notes you’re looking for.
Letting Brie Breathe Before Serving
The simplest fix for mild ammonia flavor is time and air. Unwrap the cheese, set it on a plate or board, and leave it at room temperature. The ammonia is a gas, and given the chance, it evaporates. For most wheels, a few hours is enough to let the sharpness dissipate and the flavors balance out. Three hours at room temperature is a good target for both flavor and texture: the paste softens to a spreadable consistency and the ammonia has time to off-gas.
If you’ve bought Brie that was plastic-wrapped, this breathing period is especially important. Remove the plastic as soon as you get home, rewrap loosely in parchment or wax paper, and store it in the fridge until you’re ready to serve. On serving day, unwrap it completely and give it a full few hours out of the fridge. The combination of air exposure and warmer temperature accelerates ammonia release while bringing the cheese to its best eating texture.
Choosing Brie With Less Ammonia
At the store, look for wheels that are no more than an inch thick, with a clean white rind that shows no brown or reddish discoloration. The cheese should look like it’s slightly bulging within the rind, not collapsed or sunken. Avoid any wheel where the rind appears slimy or has dark patches. Check the sell-by date and choose the freshest option available, since Brie continues ripening in the display case.
If you can, buy from a cheese counter where the staff cuts from larger wheels and wraps in paper rather than grabbing a pre-sealed wedge from the refrigerated section. The turnover is typically faster, the packaging breathes, and you can ask when it was cut. A freshly cut piece of properly aged Brie, given a few hours to breathe at room temperature, should taste rich and complex with little to no ammonia bite.