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Ammonia Odors in Cheese

By Cook's Illustrated Published September 2014

Sometimes, upon unwrapping a newly purchased fine cheese, a pungent ammonia odor will be released. Does this mean the cheese has spoiled?

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We spoke to Ihsan Gurdal, coproprietor of Formaggio Kitchen, a shop in Cambridge, Massachusetts, that specializes in fine cheeses. He explained that during the cheese-making process young surface-ripened cheeses like Brie and Camembert are coated with live mold that acts on the milk proteins, transforming the cheese from chalky and bland to creamy, silky, and full-flavored. That mold also gives off metabolic byproducts. When the cheese is wrapped tightly (as with plastic wrap), these byproducts can be trapped and concentrated over time, resulting in unfamiliar or even unpleasant smells that can be quite strong when the cheese is first unwrapped. But, Gurdal says, letting the cheese sit unwrapped at room temperature for 1 hour before serving (which you should do, anyway, since the flavors are muted in chilled cheeses) should allow those smells to dissipate. However, if the ammonia smell persists after the cheese has aired for an hour, discard it. Other warning signs of spoilage are gray, orange, or brown spots of mold (inspect the edges and sides).

In sum: Pungent aromas are no cause for concern. To minimize the issue, don’t store Brie (or any cheese for that matter) wrapped in plastic wrap. Cheese shops typically sell cheese wrapped in specialty paper that is optimal for keeping the cheese at its best. Alternatively, we recommend wrapping it tightly in waxed or parchment paper and then loosely in aluminum foil.