Nature's catalysts: Making beer with saliva

Enzymes, nature's catalysts, are essential for life. But what are they and how do they work?
23 October 2018

Interview with 

Ljiljana Fruk, University of Cambridge


The theme of the show this week is tiny molecular machines that we may not be aware of but we can’t live without, called catalysts. For some, this word brings shudders and flashbacks to chemistry lessons at school. Fear not, during the show, we are going to tickle your scientific taste buds and catalyse your interest into these impressive, microscopic chemists which are so vital for life. Here's a mini chemistry refresher: How do catalysts work and what do they have to do with beer? Ljiljana Fruk from the University of Cambridge joined Izzie Clarke and Katie Haylor live in the studio...

Ljiljana - Everywhere around us and also in our body there are continuous chemical reactions happening. That means that one compound is transformed into another compound. And this one sometimes goes fast, sometimes slow, and requires energy and special conditions, and catalysts are actually compounds that help these reactions happen and go faster and more efficient.

Izzie - Okay. So how do they work exactly?

Ljiljana - So, for example, in nature we have catalysts and they are called enzymes. They are made of smaller elements; they belong to the class of proteins, and they basically lower something which is called the activation energy of a reaction. That means every reaction, like every two people in a party, they need a certain activation energy to talk to each other. Compounds need this activation energy as well. And enzymes are mediators, they lower this activation energy so that compounds can come together.

Izzie - So where do we get these enzymes?

Ljiljana - So, for example, we have them in our mouth, we have them in our body. They are everywhere in nature. So if, for example, you had some potato or pasta for lunch today, the first thing that would happen when you put them in your mouth there will be an enzyme that will degrade the large compounds which are in potatoes into the smaller sugars, and then it can travel around the body.

Izzie - So that’s all in our mouth, in our saliva, and that’s what’s there?

Ljiljana - Yes. And then there is in the stomach, liver is absolutely full of different kinds of enzymes because liver is basically helping us to keep safe and healthy, and it’s a cleaning organ of our body.

Izzie - Okay. Now I’ve noticed you’ve got some beer with you as well.

Ljiljana - I do.

Izzie - So tell me what does this have to do with catalysts?

Ljiljana - Well, usually in a beer is made of cereal and barley is one of them. And barley has lots of different compounds which need to be degraded into the smaller elements and also alcohol because beer contains alcohol and different aromas, and to help us to do this we usually take yeast. Yeast has lots of catalysts, lots of enzymes to do that.

Izzie - That just speeds up that reaction?

Ljiljana - Speeds up the reaction and makes it go much faster than usual. I have a very special beer here made by an artist and it doesn’t use yeast, but it uses saliva. This is an artistic project. She claims that there will be a character that you can feel in this beer. And basically the enzymes for saliva are used to transform the compounds into the alcohol. And I think we should try some.

Izzie - Okay. We’re going to do this. So instead of having yeast, we’ve got saliva to ferment this beer?

Ljiljana - Yes.

Izzie - Okay. Let’s give it a go.

Ljiljana - And so this is beer with a character. So let’s try some. Okay.

Izzie - Oww woo. The beers just sort of gone everywhere.

Ljiljana - This is very good - the character is all over the place.

Izzie - I mean, that’s certainly one way of putting it.

Katie - Go on then, pass some over here. It’s quite cloudy isn’t it?

Izzie - It looks more like cloudy lemonade.

Izzie - Yeah

Ljiljana - Yes. It is cloudy because it has lots of small compounds which are transformed with the help of the catalyst and so it’s very organic as well.

Katie - It smells interesting.

Izzie - Here we go. Katie, cheers.

Ljiljana - Who's going to be the bravest?

Katie - I think it’ll be Izzie.

Izzie - Oh gosh!

Ljiljana - You see, it’s kind of refreshing.

Izzie - Umm. I mean that’s certainly one way of putting it. I wouldn’t say it’s a beer essentially. It doesn’t taste like beer.

Ljiljana - Yes, exactly. Beers can have different aromas as well. So this would be a little bit lighter, although it’s a Brazilian donor.

Izzie - How has this actually been made? How do you get a few products? So someone just spat into a bottle, what’s going on?

Ljiljana - The artist that made this, Clarissa, the beer has used a similar principle to how you would basically brew anything else. So she used cassava as a main ingredient. For beer we would use barley or any kind of of cereal. And then she added a little bit of sugar to it. If we use a good barley we don’t necessarily need sugars because there are already some kind of sugars in it, and then she added saliva. And saliva is full of different enzymes that can cleave the cassava ingredient into smaller pieces, and one of the smaller pieces will be also alcohol. And there will be a little bit of an aroma and there will be also a little bit of bubbles, you notice?

Izzie - Yeah. I did notice that, it was fizzing away.

Ljiljana - Yeah. So bubbles are CO2 or carbon dioxide which is also produced in the reaction.

Izzie - Okay. So where has this saliva come from?

Ljiljana - All of these molecules are important for our psychology, so they determine our mentality, our character because they regulate the production of hormones in our body. That means they control a little bit of our feelings. She got four volunteers to give the saliva so you can have four different beers. Currently, this is the only bottle in the UK.


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