what’s the crack?
Here’s where the magic happens
Armed with Google maps & Wikipedia, you can find out pretty much anything about a coffee, from the soil PH it’s grown in to the name of the farmer! So why is the roasting of the bean itself such a seemingly dark art? In this blog, ohco looks to lift the lid on some of the voodoo they do.
Once upon a time, every importer roasted Arabica beans in exactly the same way, and lo, every cup tasted pretty much of a muchness. Now a blend’s tasting notes can look like a fiendishly difficult recipe from the final of Bake-Off. But how do make a virtue of vanilla, or add a touch of toffee — and make a blend stand out from the roasts of the rest? OHCO founder Paul Taylor thinks it’s as much art as science. (No wait! It’s the other way round?).
“Hah! Yes of course there is a lot of airy language around seemingly random things like “blueberry tones” when it comes to coffee”, laughs Paul, obviously having had his fair share of conversations about salt caramel biscuit finishes, “but as a coffee maker, you can’t really get to that without knowing some of the science. My background was in making very complex food production processes, so I know that a great process can’t save a poor ingredient — but equally, a poor process can ruin a great one.
You’ll need a pen for this bit…
“Despite its small package ‘form’, the bean, coffee is an incredibly complex ‘thing’ ” he continues. “There are some thousand odd chemical compounds in it, of which seven hundred odd are odorants, that is, an element that contribute to aroma and flavour. And when you roast a coffee — Strecker, trigonelline, sugars, acids, amino acids and lipids degradations, caramelization, Maillard reactions — these are all things that are occurring in that single twenty odd minute process – really it would give any chemistry professor a headache [laughs].
“So it’s hard to learn how to do your first roasts. And there’s a lot of trial and error, especially if you want to make something a little different, or really maximise a particular characteristic. And there’s very fine windows timing wise, a roast can go from being a very dark and rich roast, to burnt and bitter in seconds. I should know, I’ve thrown a lot of coffee away from pushing a roast too far or not paying enough attention. Just… don’t answer your phone while roasting is all I can say!
“So there’s real science — for instance what we perceive as ‘nuttiness’ comes from thiophenes, oxazoles, pyrazine, thiazole — but in the end it’s all about the actual taste, and that’s when a little bit of that “hipster art” comes in.
“Just…don’t answer your phone while roasting is all I can say!”
Cracking on
Once you’ve got a bit of grounding in what is actually going on chemically, you can get a feel how to produce a particular flavour profile. This bit is really down to what’s called ‘the crack’.
“This process is a bit similar to popcorn-popping. Basically the water in the bean expands, finally ‘cracking’ the outer shell and releasing itself as steam. Obviously, how much energy, ie temperature you put in, and how quickly, dictates when this happens, and so also how quickly and how strongly those chemical processes occur before the crack begins. We call that energy input the “Rate of Rise” (ROR).
“Again you could really go down the rabbit hole on this process but think of two extremes. With a very low ROR, a lot of processes don’t really develop, or can even not happen at all, and so you get a cup that’s very ‘thin’ tasting and probably a bit unpleasantly acidic. Conversely, dial in the temperature too quickly, and the centre of the bean can still be almost raw when the outer shell cracks from the heat, with the resulting blend being very ‘green’, think a mouthful of peas, and probably a bit smoky, though more of an ash-like feel.”
My head hurts, what does it all mean?
“In the end, what we’re looking to do here at OHCO is really understand the individual beans we get from our suppliers” says Paul. “So when we get a new batch in, even if it’s a supplier and coffee we know very well, we use those first roasts to gauge the profile of that batch because factors like — a wetter year, slightly earlier harvest, weather patterns — they can all change the balance of those thousand odd chemicals ever so slightly. So you can’t just have preset that says “Arabica” for example, because you’ll never make the most of those great flavours waiting in that exact sack that’s in front of you.
“Ultimately, we just want our customers to know we’ve put real hard yards into every bag of coffee we produce — there’s nothing industrial about our processes, each batch is really made with a lot of know-how, a lot of love — and being honest, a lot of trial and error when we started. And it’s something we’ll never see as ‘finished’. We’re always learning, and the feedback from our customers, and the conversations we have with suppliers, means we’re always tweaking to improve something that yesterday, we might have thought was perfect. At OHCO, we say we’re ‘Curators for the Coffee Curious’, because, well, we are as much coffee fans as our customers.”
It never ends
OK, so if OHCO customers can now tell their pyridines from their phenols (you were paying attention weren’t you?) can you explain why say, an Arabica bean tastes different to a Robusta?
“Oh” concludes Paul “for that we’re gonna need a bigger blog.”
We hope you’ll enjoy our evolving series of articles about the great mysteries we try and unravel in our pursuit of coffee perfection — so if you enjoyed this first instalment, don’t forget to sign up for our Oh No it’s OHCO newsletter, and don’t forget put your newfound knowledge to the test in our expanding range of hand-roasted blends.
From green to bean, there’s a LOT that happens to coffee when it gets the OHCO roasting treatment
