Many of you know that some of the most delicious cheeses in the world can also smell the most, well, revolting. Indeed, cheese making and aging is a process of “controlled spoilage”, and it makes evolutionary sense that we’d be turned off when faced with something rotten.
It was Leon-Paul Fargue, a French surrealist poet, who described Camembert cheese as “les pieds de Dieu” – “the feet of God”. I love this characterization- it simultaneously highlights the divine sensation of eating this great cheese and the disgusting smell it produces. And even more, it brings up a truism that scientists are only beginning to explore- the correlation between stinky cheese and the body.
A brief lesson in cheese making: when we make cheese, lactobacillus bacteria, which is naturally found in milk, breaks down the lactose in the milk into lactic acid. Because of the resulting low PH, the milk curdles (the liquid whey separates from the curds, which are made of fat and protein). Rennet, naturally found in the stomach lining of a young veal, is added to harden these curds so that they can be isolated and then pressed.
There are countless variables that influence the final product, such as the source of milk, or the manner in which it’s aged. But one of the most important things that makes each cheese unique is its strains of bacteria, which are often added to the milk during fabrication or to the surface of the cheese as it ages. As I’ve described before, affineurs work as gardeners, controlling which microbes colonize the cheese.
Through the millennia, cheese makers and cheese agers have cultivated their gardening expertise and passed on both their know-how and the microbes themselves (through preserving samples of milk and smearing from one cheese to another). Yet modern science has opened up entire new pathways to explore this ‘gardening’ knowledge. While we still don’t understand the full complexity ecosystems existing on every type of cheese, we’re finally examining a cheese as an ecosystem and attempting to isolate the individual microbes. The hope is that cheese can be used as a smaller-scale model for exploring how microbial ecosystems- like that of the larger human body- work.
Cheese actually shares much, in terms of microbes, with the human body. In any human body you can find milk-curdling lactic acid bacteria, and many aged cheeses are washed with salt water throughout aging- cultivating bacteria that are also suited to the moist environment of human skin. For example, propionibacterium, which is used to make Swiss cheese, is also found in the human armpit and greatly contributes to its smell. Limburger cheese contains a bacteria that is very closely related to the one influencing the smell of human feet. Because cheese making is a very physical process- with humans using their hands and arms throughout fabrication and aging- scientist Christina Agapakis speculates that many of these cheese microflora actually came originally from the human body. As she states, “our bacterial symbionts have come to be part of our culinary treasures… bacterial and human cultures co-evolve”.
Agapakis has done one of the coolest things ever: she’s made human cheese. She’s a big proponent of what’s called synthetic biology, where scientists experiment by putting cells and cell components together in a new biological context to learn more about how these systems work in nature. To explore her hypothesis that cheese microflora evolved in conjunction with human bodies, she made cheeses with bacterial cultures isolated not in a lab and sent through and distributor, but directly from the human body. She swabbed hands, feet, noses and armpits, inocculated the samples into cow’s milk, and then made fresh cheese.
Like all cheeses, hers were shaped into distinctive final products by the different origins of the bacteria, varying in texture, color and odor. Because she saw them as both “artistic” and “scientific” objects, she evaluated them based on both perspectives- in terms of odor and in terms of final microbial populations.
Many of the bacteria from human skin likely could not survive in the milk and cheese environment- yet in the end, she found that many of the ones that did survive into the final product were also found both in the human body and in standard cheeses, as well as in cheese flavor additives and in cheese spoilage. The graphs below were taken from her article- they display not only the correlation between cheese scent, cheese microbiology and the human body, but the correlations between bodies, cheeses and the outside world.
While I understand next-to-nothing about microbiology, I’m still impressed. There’s something about this experiment that haunts me, and it’s more than the fact that camembert and feet really do have a lot in common. It’s the idea that we’re connected evolutionarily and microbiologically with the world around us and the foods we eat, and the idea that both cheeses and humans serve as ecosystems for entire worlds of beings.
It also seems relevant now, after a century in which hyper-sanitation has led to the death of not only great raw-milk cheeses (in America) but also countless medical problems due to the overuse of antibiotics (resistance, digestive problems, etc). Some of us are moving beyond our closed-minded rejection of all that is ‘bacterial’ and beginning to accept the complexity of what lies beyond our sight. Agapakis has combined art and science and food and disgust to open our eyes to our own to reservations- to really smell the stinkiness- which is, as she says, “an ancient biological communication tool”. Without it, we’d lose more than the stinky feet of God- we’d push ourselves further and further away from our complicated symbiosis with the natural world.