Bacteria With Your Brie? Microbes in Your Mozzarella?

Blessed are the cheesemakers.

When portrait photography first came into vogue in the late 19th century, the fashion was for subjects to not smile but, instead, keep their mouths small.

And photographers reportedly encouraged this by instructing their sitters to “Say prunes.”

More recently, of course, we’re inclined to smile for the camera, so “prunes” became “cheese” when it was realized that saying cheese supposedly forces your mouth into, well, a cheesy grin.

This short lesson on Victorian photography’s tie with dried plums brings us to cheese, a food that owes its very existence to those little organisms we’re proud to spend our days with here at uBiome.

Yup, microbes.

You see, you only need four ingredients to make cheese: milk, salt, rennet – and microbes.

The earliest cheeses were made around 7,000 years ago, largely by accident.

To make cheese, you need that third substance, rennet, which is a complex of enzymes found in the fourth stomach chamber of unweaned calves.

What? How the heck would you find something like that accidentally, 7,000 years ago?

Well, it seems to have resulted from milk being transported in bladders made from ruminants’ stomachs, which already contained rennet.

Next time you complain about the weight of that gallon jug of milk you pick up at the supermarket, count your blessings that at least you don’t have to stagger home with a bulging cow’s stomach.

Adding rennet to milk causes it to coagulate, and separate into curds (the solid) and whey (the remaining liquid.)

Not to be confused with WHEY, a North Muskegon, MI, radio station.

It’s the acidic nature of rennet that causes the milk proteins to tangle — or curdle — into solid masses, known as curds.

These curds are then pressed into their final form, ready to be aged, or ripened.

So what of the bacteria, then?

In the US, it’s usual to start the cheese-making process with pasteurized milk, in which case lactic acid bacteria must be added in the form of a starter-culture.

This came about in part after the FDA mandated in 1987 that all milk and milk-products for human consumption must be pasteurized.

The only exception was that cheese could still be made from raw milk, provided it was aged for at least 60 days and clearly labeled.

Using raw milk means it already contains Lactobacillus bacteria. No need to add it back.

However, many domestic cheesemakers have tended to play it safe by using pasteurized milk and adding starter-cultures, which tend to contain just a few types of bacteria, and which in the US have historically been supplied by big multinational corporations best known for selling chemicals.

Traditional cheeses, on the other hand, are inoculated with whey from previous batches, so they can include dozens of types of microbes — some unusual — which plays a big part in how a cheese tastes and smells.

There are two principal types of lactic acid bacteria – Lactococci, which are sphere-shaped, and Lactobacilli, which are rod-shaped — but Streptococci may also be involved in the initial cheese-ripening process.

Once it has done its job, the majority of this bacteria dies naturally, but it can be inclined to survive in some Alpine and hard cheeses such as Emmental, Gruyere, and Pecorino — contributing to their flavors.

Another type of cheese-related microbe is propionic acid bacteria, specifically Propionibacterium freudenreichii subsp. shermanii, which digests acetic acid, converting it to sweaty-smelling propionic acid and carbon dioxide.

It’s this carbon dioxide that creates a cheese like Emmental’s characteristic holes, while the propionic acid contributes to the complex, sharp smell of some cheeses.

Interestingly, some species of Propionibacteria are found on human skin and can help to cause an unpleasant “unwashed” odor.

In addition, there are the microbes known as smear bacteria that are responsible for some of the cheese shop’s stinkier products like Münster and Limburger.

One of these species is Brevibacter linens, which is unable to live in acidic conditions, meaning it can’t survive in the interior of cheeses. It is technically known as the paste, as opposed to the rind, formed on a cheese’s surface.

B. linens requires salty conditions, so its bacteria are encouraged through the continual washing or wiping (smearing) of the surface of the cheese, enabling the B. linens to break down proteins into some, quite frankly, stinky substances.

These washed-rind cheeses have an odor like smelly feet, which is perhaps no great surprise, as Brevibacter can also be found on unwashed human skin.

A soft cheese like Camembert is made by inoculating warmed cow milk with bacteria and rennet, then (after packing the curds together) spraying its surface with a solution containing the mould Penicillium camemberti, producing the cheese’s distinctive edible rind.

Mentioning Camembert, of course, is a fine excuse to celebrate the famous Monty Python Cheese Shop sketch (there’s a link below) when the hapless assistant, Mr. Wensleydale, dissuades his customer, played by John Cleese, from buying the one type of cheese the shop has in stock (Camembert) by warning him, “I think it’s runnier than you’d like it, Sir.”

After decades of relatively bland supermarket cheeses here in the US, we’re delighted to see an upswing of small cheesemakers with their hearts set on creating products with more complex, European, bouquets and tastes.

One of these is Jasper Hill Farm, a creamery in Greensboro, Vermont that, despite its relatively small size, has ramped up its learning by installing a state of the art microbiology laboratory.

Constantly experimenting with different bacteria, constantly taste-testing the results, Jasper Hill Farm is employing the same kind of genomic sequencing we use it uBiome to identify the precise mix of bacteria present in the cheeses that are the bees’es knees’es.

So let’s hear it for those microbes, then.

The last word, however?

Well, it must go to a friend of ours, who admits to having an addiction to Cheddar.

He does say it’s only mild, though.

More reading


Cheese Shop Sketch – Monty Python’s Flying Circus


History of Cheese

Jasper Hill Farm

Microbes and food. We are what we eat. Cheese.

Raw Milk State Laws and Regulations – Real Raw Milk Facts


Say Cheese

Saying cheese as style curiosity – Yearbook photos studied

Serious Cheese – Know Your Microbes

Small Cheese Makers Invest in a Stinky Science