Queasy Cheesey

Cheese. Like wine, there are just so many different kinds. One to suit every palate! We all love it and I’m in good spirits so open up your disk drives people, as one famous videogame god put it- “Cheese for everyone!”

Wait…what’s that? Not everyone loves it? Well, ok…Most of us love cheese. So cheese for some of us. But as a treat for everyone, let’s answer a simple question. How is cheese made?

To start with the basic ingredient of all cheese is milk. Any milk. Cow’s milk, goat’s milk, yak’s milk, even human if that tickles you (there are a few cheese makers who use human breast milk to create their cheeses). Like different varieties of grape make different wines, milk gives each cheese a base for their particular flavours and textures due to the unique quantities and ratios of fats and proteins.  The art of cheese-making is very intricate and these qualities are combined with numerous seasonings, herbs, ageing times and other processes to give the final product its finished flavour.

But first the milk must be ‘ripened’. This is simply an acidification step to encourage the next stage of the process and can be as simple as adding lemon juice (the active ingredient being citric acid) to the milk. More commonly, and arguably for better quality, bacterial cultures are added to the milk after pasteurisation (heat-sterilisation) instead of citric acid. These bacteria are used for their fermentation capabilities; they can anaerobically respire to produce lactic acid for the ripening of the milk. This is a key step, so hold this in mind!

Next, Rennet is added to separate the milk into curds and whey. Rennet is an enzyme traditionally harvested from the fourth stomach of a baby cow, but nowadays plant-derived Rennet is available for vegetarian-friendly cheese. The semi-solid curd is the concentrated fats and proteins found in milk, while the whey (normally discarded) is the remaining water and few highly soluble compounds that resist the enzymatic actions of Rennet. After this it is simply a cyclical process of salting, drying, pressing and processing the curds to obtain the particular cheese you desire. Some of it is simply common sense; softer cheeses require less pressing for example.

Like we said, bacteria are used to acidify the milk to encourage the actions of rennet and the formation of the semi-solid curds but they also give other contributions to the final product. In the cheese-making industry there are two species of lactic acid bacteria (that’s bacteria that produce the otherwise eukaryotic product lactic acid found in our muscles during exercise, from fermentation) that are commonly used to ripen the milk and, sometimes, thrive in the cheese themselves.

These are Lactococcus lactis and Streptococcus thermophiles. Both were previously members of the Streptococcus genus (like Streptococcus pyogenes, the bacteria responsible for Strep Throat and Scarlet Fever) before one was reclassified as Lactococcus. L. lactis are gram positive, non-motile chain-forming spheres commonly used to produce Brie, Cheddar and Cottage cheese, and thrives in Blue Cheese alongside the normal blue mould that gives it its flavour.  S. thermophiles on the other hand is an alpha-haemolytic (‘partial red blood cell lysis’) species that is used for the ripening of cheese but one that cannot survive the strong stomach acids of the human gastrointestinal tract3. Both of these bacteria are naturally found in milk and dairy products and have been used for decades, if not longer, in the making of the cheeses we all know and love.

 I may have used some slight hyperbole, there. This Figure clearly doesn’t detail how L. lactis can produce such different cheeses; remember it is the cheese-making process of pressing and aging etc. that dictates this, but it does demonstrate how this bacterium can contribute to the taste of two very different cheeses. Compare Brie against Cheddar (Left and right bottom respectively). Brie is a soft, creamy cheese easily spread on crackers (also delicious with bacon for a posh sarnie) while Cheddar is a solid, tangy cheese.

L. lactis can contribute to the taste of very different cheeses. Remember it is the cheese-making process of pressing and ageing etc. that dictates how the different cheeses are made. Compare brie versus cheddar (left and right bottom respectively). Brie is a soft, creamy cheese easily spread on crackers (also delicious with bacon for a posh sarnie) while cheddar is a solid, tangy cheese.

But let’s go one step beyond.
Scientists and, oddly enough, artists (because who says there’s no beauty in science?) have teemed up to make some really odd cheeses. Are they aged underwater? Pressed by blind monks? Wrapped in Himalayan Sloths until they’re ripe?  No.
These cheeses are made from you. Specifically, the bacteria growing on you.

That’s right, biologist C. Agapakis and a team of colleagues have created 11 cheeses for an art exhibit entitled “Grow Your Own” using bacterial cultures swabbed from human armpits, tears, belly-buttons and other areas of the body. These bacteria are used for the acidification and maturation of the cheeses but also highlight the intricate relationship between nature and culture (bacterial culture- get it?). It also highlights how similar the microflora of different individuals are; reflected in the fact that all swab samples could ferment the dairy sugars (like lactose) to produce the cheeses on display. Unfortunately, these kinds of cheese aren’t available for public consumption so you food crazies out there won’t be able to try some any time soon.

Although the samples, all from different parts of the body, do indeed share some microbial species (or at least similar genera/function), as evidenced by the lactic acid production for the making of the cheese, there are major differences between them. If you look at some of the created pieces from this art exhibit you’ll notice many have similar but subtlety different appearences/textures. This suggests slight differences in the species that reside at these bodily sites, and although many scientists already know this and can show it using dry and complicated graphs, it’s nice to demonstrate this fact by a simple show that everyone can enjoy and appreciate. Whether you’re a lover of cheese or not.

 

References

Home, Food and Kitchen, Cheese making Basics, Hobby Farms.com http://www.hobbyfarms.com/food-and-kitchen/cheese-making-14872.aspx

Guide To Home Cheese Making by Robert Carroll, 1986 http://www.motherearthnews.com/real-food/home-cheese-making-zmaz86mazgoe.aspx?PageId=7

Textbook of Bacteriology, Lactic Acid Bacteria (page 3) http://textbookofbacteriology.net/lactics_3.html

Figure 1-
For SEM image of L. lactis;http://textbookofbacteriology.net/lactics_3.html
For Brie image; www.dairygoodness.ca(Google Image “Brie”, 12pm on 19.6.14)
For Cheddar image; www.theguardian.com (Google Image “Cheddar”, 12pm on 19.6.14)

National Geographic Daily News, “Human Cheese’ Only The First Course For Odd Cheeses”, http://news.nationalgeographic.com/news/2013/12/131202-human-cheese-food-biology-weird-gastronomy/

Daily Mail Online, “Would You Eat Cheese Made From Human Feet And Armpits?…” http://www.dailymail.co.uk/sciencetech/article-2511272/Would-eat-cheese-HUMAN-FEET-ARMPITS.html

CNet, “Cheese Made From Human Toe Jam, Belly-button Bacteria” http://www.cnet.com/uk/news/cheese-made-from-human-toe-jam-belly-button-bacteria/

New Scientist “Armpit Cheese: The Sweeter Side Of Bacteria” http://www.newscientist.com/article/mg22029482.000-armpit-cheese-the-sweeter-side-of-bacteria.html

feature image photo credit: Renée S. Suen via photopin cc

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