The science of cheesemaking

Let’s turn to another delicious and popular food made by fermentation - cheese! Michael Tunick is a cheese scientist at Drexel University, and, as the author of ‘The Science of Cheese’, he has literally written the book on the subject. Hopefully he’s going to be able to tell Chris Smith why some of the cheeses he loves - and has brought with him into the studio - have the terrific flavours that they do...

Michael - It starts by taking milk and adding bacteria to it. And that will start to digest the carbohydrates in the milk and produce lactic acid. That's the same thing that happens when milk goes sour, but the cheesemaker will stop it from getting that far. And we'll also add rennet, which is an enzyme which will break one particular kind of protein in the cheese. And that causes the milk to coagulate into curds and whey, the curds being the solid part. And then the cheese maker will heat up the curd, and cut it into cubes, and they work with it to squeeze out more whey, and then they'll press it and store it. And there's hundreds of different ways of doing this. And that's why you will have hundreds and hundreds of different kinds of cheese in the world.

Chris - When you said they heat it up, do they heat it up enough that it actually destroys the microorganisms as well? Or do they survive that process?

Michael - They'll survive that process, it doesn't get heated up much higher than 45 degrees C. So the microbes will survive, and they want them to, because they want them also to start attacking the fats and oils in the cheese. Because they produce a lot of flavour compounds, and also you still get them attacking the protein. And so you got flavour compounds out of that too, and the carbohydrates will produce something also.

Chris - So the maturation process, when the cheese is left a time to mature, that's when all those complex and tasty flavours are developing because of the ongoing action of the microorganisms, it doesn't stop once they've just made a basic cube of cheese.

Michael - That's correct. And it depends on how they store it, whether you have it left unwrapped or whether they put wrapping over it, or if they put wax on it, and then you have the temperature and the humidity to take into account. And of course, how long you have it stored. So some cheeses can be stored for just a couple of days, but you have parmesan, which can be stored for a few years before they send it out.

Chris - I'm glad you brought this storage question up because I've actually got sitting in front of me here, I've brought my cheese platter along with me. And I have sitting on it some cheddar, of course named after Cheddar the place in the UK where cheddar cheese is said to have originated, there are caves there. And one of the other cheeses I've got in front of me says it was cave-matured at Wookey Hole. And I thought this was just sales speak, but is there actually genuine science there then, that actually those caves do contribute to the cheese flavour.

Michael - Yes, because you have yeast, but especially moulds in caves. And so they can settle on the surface of the cheese and start eating the cheese and producing these compounds. So that's where you get things like Roquefort. That has to be stored in the caves in Roquefort, France or otherwise you can't call it Roquefort cheese. And there's other caves around that are used for the same purpose. That's a good constant temperature, constant humidity place. You don't have to go build a building to do that.

Chris - As I say, happy to have in front of me, my cheese board. So maybe you could actually talk me through some of what's on here and why it is the way that it is because I have a piece of cheddar, as I mentioned now, this is quite a hard cheese, quite strong, sharp flavours. I've got some Black Bomber here as well, which is one of my favourites and sitting next to it. I thought we'd go for something local, totally different. Some Cambozola, which has blue cheese. And I've also got some, because we've got to keep the French people happy, some Port Salut. Now they're very different textures, the blue cheese, and the Port Salut are quite rubbery in texture. Why are they rubbery, and the Cheddar's quite hard?

Michael - Depends on the protein breakdown, that the cheddar is allowed to age for a while. So the matrix of protein in there gets to be broken down a bit. And you also lose a lot of moisture. So the cheese is going to wind up being kind of hard and crumbly. The others, they try to keep more moisture in there. So that's going to be softer and just the way they make it will be a bit more rubbery in texture, then the cheddar will be. Parmesan doesn't have much moisture at all. So that's one that you can grind up, but you have others where they're really soft, some goat cheeses, which are really smeary. So texture is a lot to do with how people enjoy cheese too, not just the aroma and the flavour.

Chris - And I've brought a blue cheese. Cambozola is a blue cheese. How do they actually get the blueness in there? And where does the blueness come from? Why does that not happen naturally, anyway?

Michael - The blueness comes from the mould powder that they add to it, used to be that they would have the cheese sitting in the cave and allow the mould to settle on it, as I just mentioned, but nowadays they'll take mould powder and they'll mix it in with the milk while the cheese is being made. So you have mould scattered around the inside of the cheese and while the cheese is aging, they'll also skewer it. They'll pierce it to allow oxygen in, to allow the mould to grow. Depends on what kind of mould you have. The cheese that you have is going to be a kind of blue. You'll have other moulds, which are going to make kind of green veins in there. The Cambozola is made kind of like a Camembert with this yeast mould mixture applied to the outside, but you also have this mould on the inside, which is like a Gorgonzola. So that's the combination. That's where you get the name.

Chris - One quick question. I've been dying to ask you, which is, there is this claim that blue cheese before bedtime translates into funny dreams. Is there actually any truth in that, or is that just of those stories that improves with the telling?

Michael - That's one of those stories that improves with the telling. I don't see anything out there which shows that cheese affects the way you sleep. So, it affects your nutrition in a good way, but I don't think it affects your sleep.

Chris - I'm very pleased to hear that. And in the last 20 seconds or so I've shared my three favourites, what are yours?

Michael - That's kind of like asking me which children are my favourite. Any cheese that, you know, has a good flavour to it and a good aroma and so forth. So, right now this minute, my favourite is Manchego that I picked up at the supermarket a couple of days ago, my wife and I just finished that off immediately, but it'll vary from one week to the next, whatever I encounter that tastes good.