The Science of Brie Cheese

One of my favorite snacks is a generous quantity of brie on a piece of good rye bread. It's a fantastic cheese for a daily treat, and a fabulous party food. While it's not exactly an everyday food in the United States (although it's available in every major grocery store I've encountered), and its French heritage lends it an air of sophistication, its creamy textures and buttery flavors make its appeal quite accessible (as opposed to some blue cheeses, which are more of an acquired taste). These virtues aside, I think one of my favorite things about brie is the science behind its production.

The production of brie starts out similarly to that of many other cheeses; cow's milk is curdled by adding rennet and heating it to 37 degrees C (98.6 degrees F) to produce curd. Rennet, traditionally extracted from calf stomachs (plant- and fungus-based alternatives are now available), is a complex of enzymes which break apart the protein casein, which is very abundant in milk. The casein is broken into two parts; one of the two parts is responsible for the coagulation that forms the cheese curd, and the other part becomes part of the whey, contributing to its protein content.

The curd is extracted using slotted ladles and placed into molds, then allowed to drain for hours or days. The cheese is then removed from the mold, salted, and several different types of microorganisms are introduced to the surface of the cheese. Because the cultures of these organisms are smeared over the surface of the brie, it is referred to as a surface-ripened cheese; some other cheeses are innoculated with the organisms by being stabbed with culture-coated prongs to ensure deep penetration of the microbes into the cheese.

Many of the articles and websites about cheese production that I have found have betrayed a certain level of confusion among cheese enthusiasts and makers regarding precisely what types of microorganisms are used to ripen cheeses; arguably that knowledge isn't terribly important for them, as it doesn't really impact their interaction with the cheeses, but as a former biologist, I think that the identity of the organisms used and how they ripen cheeses is one of the most interesting parts of brie production.

Brie is ripened using both bacteria and fungi. The bacterium Brevibacterium linens is normally abundant on human skin, which suggests how it was introduced into ripening cheeses before people knew about bacteria; apparently early cheesemakers put more of themselves into their product than they realized. Penicillim camembertii and Penicillium candidum, two species of soil fungi, are also applied to the cheese. As evinced by their name, these species are closely related to Penicillium chrysogenum, which produces the antibiotic Penicillin. The fungus is visible on the surface of the brie as the characteristic white, slightly fuzzy (and completely edible) rind. As you may have guessed from the name of P. camemberti, these organisms are also used in the production of camembert, which is very similar to brie.

The bacteria and fungi both secrete enzymes to help digest certain components of the cheese. As the cheese is ripened over the course of several weeks, they break down some of the fats and proteins in the cheese, giving the cheese its gooey texture and nutty or buttery flavor. The microbes release various byproducts of their digestion, including small amounts of ammonia, which contribute to the cheese's flavor and aroma.

While the chemistry which goes on inside a ripening wheel of brie is fairly nuanced and complex, the actual process of cheesemaking is not so complex that your average cheese afficiando cannot learn to do it at home. There are many books with excellent instructions available, many websites filled with tricks and tips for cheesemaking, and in many cities, there are classes or clubs devoted to cheesemaking filled with people eager to help you start making your own cheeses.