WHEN it comes to finding new and exotic species, there is no need to travel to the rainforest or trawl the deep ocean. Just open your fridge. The cheeses in there contain a wealth of surprises, if you look closely enough.
Although cheese production , we are only just beginning to understand what is really going on in this complex ecosystem that we delight in devouring. “Cheese is a fascinating ecological niche,” says , a microbiologist at food and agricultural research body Teagasc who is based in Cork, Ireland.
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New work on the cheese microbiome is revealing a riot behind the rind, with complex interactions between a diverse array of bacteria, moulds and yeasts helping to create characteristic flavours and textures.
“There are a lot of microbes that we’re eating every day on some of our favourite cheeses, and we know incredibly little about what they’re doing to drive the flavour of those cheeses,” says . Understanding this better will not only help control the flavours of existing cheeses, but also help us develop tasty new ones.
Here’s a tour of some of the surprises hidden in your cheeseboard.
Exotic menageries
Cheeses are dominated by bacteria that digest the main sugar in milk, lactose, and turn it into an acid. But they are also home to a menagerie of other microbes that develop as cheese matures, and exactly how many organisms cheese contains is only just being revealed.
Studies using gene-sequencing technologies keep finding new bacteria, some previously unknown to science. A , for example, found they were home to 159 different strains, only 16 of which were common to all.
One surprise has been how many bacteria found in cheese originate from the oceans. “We find them again and again,” says Wolfe. “We have no idea really what they’re doing to affect the flavour of cheese and we don’t know how exactly they’re getting to the cheese.” The presumption is that they catch a ride in the brine the cheese is washed in.
One particularly exotic salt-loving marine bacteria found in cheeses is Halomonas. “Some are more extreme in terms of the levels of salt they can cope with” says Cotter. “They’re more typical of the Dead Sea.” The challenge now is to figure out how these microbes contribute to the array of compounds that create cheeses’ flavours.
Going mouldy
Eating mould may not be your idea of fine dining, but when it comes to cheese, it is a prized ingredient. The most famous moulds are Penicillium roqueforti, responsible for the blue veins in Roquefort and Stilton, and Penicillium camemberti, which creates the fuzzy white rind of Camembert and Brie.
Two recent studies by researchers in France revealed how these fungi have been domesticated from the wild variety, in the same way that humans bred dogs from wolves by selecting favourable characteristics.
P. roqueforti has . The first strain is slow growing and used only in the production of Roquefort, whereas a more recent domestication is responsible for a faster-growing strain used in all other blue cheeses.
P. camemberti has , when a wild, blue-green fungus was domesticated to produce the grey-green mould used to make many cheeses, such as the Golot cheese of Turkey, and again in around 1900 to produce the characteristic white mould used in Camembert.
In the cheese ecosystem, moulds can work with other organisms to form particular flavours and textures. In Stilton, for example, P. roqueforti , known for its ability to break down lipids and proteins. This boosts the number of ketone aroma compounds, characteristic of smelly blue cheeses.
Gene-swapping orgies
The cheese on your plate is a den of gene-thievery. In the thousands of years since cheeses were first created, the microbes that make them have been rampantly swapping genes as they evolved to survive in this new environment.
associated with cheese found that 80 per cent of them had acquired genes directly from others through a process called horizontal gene transfer. Many of these genes were involved with scavenging iron, a rare commodity in cheese. “Iron is incredibly limiting in this environment,” says Wolfe. “The winners are really those that have the ability to quickly find the iron.”
Warfare
It is a battle for survival in cheese, which means organisms need some weapons up their sleeves. A of 55 artisanal Irish cheeses revealed that around 20 per cent of microbes in those cheeses contain genes for compounds called bacteriocins that kill their rivals. This is far higher than the 13 per cent found in our gut, for example, as well as other environments. “We were a bit surprised,” says Cotter.
“The rind, from an ecological perspective, is particularly fascinating”
Another inside-the-rind evolutionary arms race involves bacteria and viruses. About 20 per cent of the organisms living in cheese are bacteriophages, viruses that infect bacteria. But Cotter and his colleagues’ are armed with a defence mechanism called CRISPR to destroy bacteriophages, while the viruses are equipped with anti-CRISPR proteins to dodge these attacks.
The top dogs of the cheese microbiome are fungi. “In these communities where you have both fungi and bacteria living together, the fungi really seem to be the drivers of the interactions,” says Wolfe. “We’ve seen examples where the fungi are wiping out the bacteria through the production of antimicrobial compounds.”
But fungi don’t always win. On the rinds of certain cheeses, such as Milbenkäse, produced in Germany since the Middle Ages, fungi are preyed on by cheese mites.
The bit you throw away
The rind, from an ecological perspective, is particularly fascinating. It acts not only as a barrier, but as a controller for the microbial action within. “As the rind grows, it releases enzymes that break down the milk and produce a lot of the flavours that we enjoy,” says Wolfe.
In Camembert, for example, the characteristic surface mould P. camemberti , a key cheese flavour molecule. This diffuses into the centre, increasing the pH and ripening the cheese by degrading the milk protein casein.
But the big question is: should we eat the rind? The answer depends on what kind of rind it is, and there are three main types.
You have the fuzzy white ones found on cheese such as Brie, and the sticky, pungent ones found on cheeses that have been washed in brine, wine or beer, such as Gruyère. These might taste “funky”, says Wolfe, “but you can eat them for sure”.
The third type is known as natural rind. You might find this on blue cheeses or cloth-bound Cheddars, resembling lichen growing on the surface.”That’s more of a functional rind, to help control moisture loss and prevent bad microbes from growing on the surface and is not there for flavour,” says Wolfe. “It’s totally fine to it eat it, but I tend to cut it off.”
