Measuring Green Bean Temperature

Measuring Green Bean Temperature

WOLFF WEEKLY VLOGG 045 | Peter Wolff talks Measuring Green Bean Temperature

Hello everyone. Thank you for watching. My name is Peter Wolff and this is the Wolff College of Coffee Vlogg. Today I’m going to answer a question. A lot of questions I get asked by the people participating in our roasting courses are: what if I don’t actually have something like Cropster or Artisan available and I only have just basically a simple bean probe in the front of the roaster but I don’t really have it hooked up to anything. What sort of performance criteria can we be using.

I guess one of the things is, look at establishing how many degrees per minute. So still a ramping sort of strategy, but how many degrees per minute will the coffee need to be increasing. So the first thing that I can say is that on average it should be no less than seven degrees per minute and no more than fifteen degrees per minute, with the sweet spot falling around that ten or eleven degree mark is what I would say for a nice medium style espresso.

So one of the first things that you need to be doing is getting a stop watch or if your roaster has a timer built into it definitely make sure that you know how to use that function. I would also be getting some simple graph paper or at least downloading some simple roast logs. Every minute you need to be recording how many degrees per minute your coffee should be rising during the roasting curve. This will definitely help you track and be able to control the rate of rise.

As we’re approaching first crack, the dynamic changes a little bit and we need to be decreasing or slowing down that rate of rise. I generally like at first crack my coffee to slow down to anywhere between three and five degrees per minute. It is dependent again on the hardness of the coffee, the degree of caramelisation that I’m chasing and obviously end cup flavour.

One of the key things is the numbers really start meaning something to you as you start cupping your coffee. So definitely keep a very accurate roast log, cup your coffees at the end of every session and understand well what does eight degrees a minute mean for this coffee, what does ten degrees per minute, what does eleven twelve and so on and so forth. And so you then have an understanding of what shifts you’re getting in acidity, body and complexity.

These are some basic criteria that we can start with. If it’s a brand new roaster or if it’s a brand new profile that you’re looking to start with, first thing I generally do is get some coffee, put it straight into the roaster and normally would charge the roaster, it’s temperature, to about sort of 200C, would be my very first roast on a brand new roaster. I generally drop the coffee in, turn the burner to 100% and I just let it track all the way through. What I’m really trying to establish is what times and temperatures and more importantly what temperatures certain events are happening at. So what temperature is yellowing, what temperature is cinnamon, what temperature is first crack happening at, and I’ll let it run all the way to second crack because I know basically that’s the end of the road and I need to be well and truly before that. If you’re wanting to have a really dark and well developed roast then, well, you’ll know where second crack is. Then from that I know where I have my key temperature thresholds and then I can start creating my roasting strategy based on rate of rise with those temperature sequences in mind.

Any way, give it a shot. As I said, seven to fifteen degrees – this is for espresso based coffee – pretty well much from turning point until first crack, and when you get to first crack you really need to slow things down and really focus on shift the coffee to inner bean drying and get that down to three to five degrees per minute. I’ll be talking at a later time about filter roasts or brewed coffee. Thanks for watching, bye!

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