Coffee professionals and home roasting enthusiasts alike will be familiar with the sound of the first crack of coffee as it roasts. You can hear it on the IKAWA Pro Sample Roaster and a popular suggestion from customers has been to record the first crack during the roast on the app.
We’ve listened and introduced a very simple way to add this information.
how to Mark First Crack
While the roast is taking place the option to Mark Crack appears in the bottom left of the screen.
- Select the Mark Crack button then by pressing this
- Three options will show; 1st crack, 2nd crack or Cancel – make your selection.
It’s worth noting: The point at which first crack is recorded is the moment you press Mark Crack, rather than selecting the 1st or 2nd crack option. If after a few seconds you decide it would be more accurate to mark first crack as the later time, you can update the selection – but you can’t move it earlier than the current time.
If you wish to take the coffee to a second crack you can do this and record it in the same way.
The first crack is visualised by a vertical line on app screen showing the temperature when it occurred, and includes an icon and the time.
You will also notice a red circle below the white fan line displaying DTR. This is where Development Time Ratio is calculated.
DTR is calculated as time from First Crack to the end of the roast, as a percentage of total roast time. The DTR is continually updated after the first crack is marked, so as the roast progresses, it goes from 1%, to 2%, 3% etc right up to the end of the roast.
This provides an additional indicator of if you should shorten or extend the roast and the Pro App allows you to update the roast profile ‘on the fly’.
What is the first crack and how do you define it?
During a roast the heat of the roaster causes moisture in the coffee beans to evaporate, and as the coffee dries it expands. This causes the coffee to make an audible crack – known as first crack. At this point the beans go ‘exothermic’ briefly giving out heat, so it’s a sensitive time during the roast.
The IKAWA Pro Sample Roaster’s temperature control system quickly senses a rise in temperature in the roast chamber and automatically adds less heat so the roast continues to follow the set profile.
All beans will not crack at the exact same point – variables affecting this include roast duration, rate of rise curve, bean varietal and moisture content – so the point at which you define First Crack can be subjective can vary from user to user. We define first crack as the point when multiple cracks are heard in a quick succession. The main thing is to be consistent with how you define it.
Why is Development Time Ratio Important?
Development Time is a term that refers to the period after onset of first crack until the end of the roast. Getting the development right will mean your coffee will have balanced acidity, with excellent body and sweetness. It shouldn't display any undesirable savoury “organic” flavours and its structure will be broken down sufficiently to allow water to enter and dissolve its flavours.
The Rate of Rise of temperature during this phase is important, but so too is the amount of time the beans are roasted at this stage. With the IKAWA Pro Sample Roaster, the roast time can vary significantly from 4 minutes right up to 12 – 14 minutes at a push, so we think that looking at the development time as a ratio is a better metric.
Scot Rao talks about the ideal Development Time Ratio (DTR) being between 20 - 25% of total roast time in his Third Commandment of Coffee Roasting in The Coffee Roasting Companion. We’d be really interested to hear what DTR you find as the optimal range – with a shorter total roast time, and fast Rate of Rise possible with the IKAWA Pro Sample Roaster you may find the parameter vary.