Science Interviews


Fri, 5th Feb 2016

From bean to cup: the perfect brew

Alex Summers, Cambridge Botanic Gardens and Simon Fraser, Hot Numbers

Listen Now    Download as mp3 from the show Caffeine: Friend or Foe?

The Brits may be known for their copious tea consumption, but it was actually Coffee beanscoffee that peppered our street corners first in the 1640s. 20 years later we got tea and 80 years after that, the States adopted coffee as their drink of the choice. Of course, caffeine isn’t just in tea and coffee but can be found in energy drinks, drugs and even chocolate! But in finding out about our coffee history, Graihagh Jackson went to find out how a humble bean is processed into a delicious brew with Alex Summers at Cambridge’s Botanic Gardens...

Alex - So there are two main species of coffee that are grown worldwide - Coffea arabica and Coffea robusta.  The high quality coffees come from Coffea arabica and the lower quality, higher yields come from Coffea robusta.

Graihagh - I’m looking at the two of them - ones just a bit shorter.  They’ve both got crinkled leave like someone’s got a hair crimper and crimped the leaves for them; but otherwise they’re remarkably similar.

Alex - It shouldn’t be surprising that they look similar because Coffea arabica probably has similar ancestry to Coffea canephora or the robusta coffee.  In the case of Coffea arabica, it has four copies of the chromosomes, or the genetic material.

Graihagh - Now we all know that plants like these are famous for their levels of caffeine, but why do they produce caffeine in the first place?

Alex - It’s quite interesting; they did an experiment with a spider.  They got it to spin a web and they fed it all manner of different drugs from cocaine, ecstasy and caffeine and what they found was that the spider produced the most erratic web when it was under the influence of caffeine.  So you can truly see how effective caffeine is as an anti-herbivore agent, not necessarily so much as a case for ourselves.

Graihagh - I assume you’re not just growing it to make a lovely cup of coffee today.  Why do you have it here at the Botanic Gardens?

Alex - Funnily enough, actually, the opportunity to make a cup of coffee is great but the real reason we have it, like most of the collections here, is to provide a resource both to the university, but also to provide a resource to the public.  So in the case of coffee, we’re all familiar with it from the shops, but it’s nice to give people an idea of actually where it grows and where it comes from.

Graihagh - Beans picked, we peeled off the red flesh, dried them and finally scraped off the outer husk to reveal the green bean underneath.  Next stop was an artisan coffee shop called Hot Numbers for roasting.   So, Alex and I set off with a handful of botanical beans to meet Simon Fraser...

Simon - We’re just going to actually weigh the content of this….

Graihagh - It’s about a handful isn’t it?

Simon - It is - it’s quitie a small amount - but we’ll work with it.  I’m just going to turn the scales on - we’ll see...  We’ve 10 grams so we’ll try and make a very small filter coffee with this afterwards…

Graihagh - Simon fired up the roaster to 150OC - and not a degree more because even a couple of degrees can turn a good cup of coffee into a bad one.

Simon - It’s a glorified tumble dryer, I reckon, with a big colander underneath…

Graihagh - I have to admit it does look very swish.  It’s all sort of black and stainless steel; I would say almost steam engine like?

Simon - It is - very much.

Graihagh - A steam engine with two windows.  One where you can see the flames and the other where you can see the coffee beans jump around the drum while they roast.

Simon - We have a sample screen underneath it where we can pull out the coffee as it’s roasting.  And then, after the coffee’s roasted and we’re happy with the colour, then we’ll drop it into this big cooling tray here and that will cool the coffee.  If we didn’t do that, the coffee would carry on roasting and you would get a lot of baked flavours going on.

Graihagh - I suppose much like an egg continues to cook after you boil it unless you peel it very quick?

Simon - That’s it, that’s it. So we…

Graihagh - ...we don’t get dippy eggs.

Simon - No, No…

Graihagh - We get hard boiled eggs.

Simon - That’s it, so let’s hope not for some hard boiled coffee so…

Graihagh - With all our fingers and toes crossed, we poured the beans into the roaster.  Alex, from the Botanic Gardens, Simon and I; we all watched in awe at our hard work roll around the machine - much like clothes in a tumble dryer.  And then, the beans began to pop like popcorn.

Simon - So, we’re approaching first crack.  The beans are agitating a lot more; they're giving off a lot more energy and they’re doubling in size.

Graihagh - I can’t tell.  My non-coffee connoisseur eye can’t tell the difference.  I can tell they’ve changed colour…

Simon - I can see they’re dancing more and they’ve got a snap to them now.

Graihagh - Yes - much more of caramel… Oh yes, and I can definitely get the smell of coffee now.  That smell you associate with…

Simon - Unless…  I think you might be smelling some from that tub there actually.

Graihagh - Well it smells really nice, whatever it is.  It’s smells really good…

Simon - It’s funny because well it’s often confused because when we’re roasting coffee it's usually - you’d expect it to be the coffee smell - but it’s actually like a toast smell.  It’s like a breakfast smell that you’d get in the morning.

I’m about to drop the coffee out into the cooling tray from the drum… They’re looking a bit patchy but it’s the best we could do under the circumstances, I believe. But they got a bit of mottling and a bit of, you know, difference in colour but…

Graihagh - I would say characteristic of the Botanical Gardens.

Simon - Is that right?

Graihagh -   Yes - characteristic…

Alex - Not sure we want to own that one.

Graihagh - Patchy in colour or not, the proof is in the taste.  So we ground them up and brewed them but first, I had a quick question about the science of grinding.

In supermarkets, you might have seen that on the packaging it says “ground for french press” or “espresso” or whatever.  But do you really need to buy a different grind for different types of brewing or is this just some clever marketing ploy?

Simon - The grinder is probably most important in getting the consistency between the beans and, if you’ve got a good grinder, then you get an even surface area and the more evenness between the beans, the better the extraction.   And so yes, for espresso you want a fine grind; as you’re getting more towards the sort of mocha pot, it wants to go a little bit courser, and as you get to french press, that’s the coarsest grind.

So we’re going to grind this coffe up for paper filter…

Graihagh - Away we go…  I feel tense, do you feel tense?

Alex - Yes, absolutely  - it’s incredible.

All - Cheers!

Graihagh - It definitely is rummy...

Simon - Yes rum or almost some sort of sherry element to it.

Graihagh - See look, it didn’t taste like mud Alex!

Alex - No it didn’t.  I’m really happy, actually.  I would actually drink that.

Graihagh - How would you say this compares to what you would normally be brewing?

Simon - It’s funny because it's like nothing that I’ve tasted really and, you know, it's not bad actually - I’m really quite enjoying it.  It’s very different.

Graihagh - So if Alex was to set up his own cultivation business at Cambridge Botanical Gardens, would you buy his coffee?

Simon - Well, I’d certainly give it another go to put through the roaster but I might need more than about ten grams.

Graihagh - Alex - what do you say?  I mean, I feel like I should be a shareholder at least having introduced you guys.

Alex - Absolutely, absolutely!  I think what we’ll put to the Director is ripping out all the plants and just put in coffee right through the tropical houses.


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