I am seated at Paronworks, a coffee roastery in Bali, Indonesia run by Pak Yudhan. He has been roasting for over 4 years and today after a cupping session he has decided to share his knowledge about the perfect coffee roast profile.
Before we start spilling the beans on the perfect roast profile, let us tell you that roasting isn't easy! Coffee is a very multifaceted product and becoming an expert roaster will take you time and many trials & errors along the way.
Back to Roast Profile Basics: The S-Curve
Before you start roasting, it's a must to understand at what exact temperature your roaster will hit the first and second crack. This provides you with a time window for a medium-style roast.
Timing wise, your first roast should complete within 8-14 minutes, with the first crack at around 8 minutes, depending whether this is your first roast of the day.
This diagram shows the basic S-Curve roast profile. As you can see, temperature is on the Y-axis and time on the X-axis. Take note that the temperatures always depend on the thermometer in your roaster. You can add them to the graph once you’ve worked out where they fall for you and your machine.
[Image: Food Science Dept., Univ. of Massachusetts, Amherst, Mass. United States]
S-Curve Roasting Guide
Coffee roasting isn't easy and it will take quite abit of trial and error until you get your first roast right just the way you like it.
Drop temperature refers to your roaster when you load your beans and start the process. During this time, you should keep the burners low. The coffee beans will absorb heat with only a tiny amount of help from you.
[Image: Dropping them beans]
Turning Point (TP) & Rate Of Rise (ROR)
If you check the graph posted above you can clearly see that the temperature immediately plummets after starting the roast. Naturally, the cold coffee will absorp the heat from your roaster, hence the temperature drop.
A few minutes later you will reach the Turning Point (TP). This happens when your beans have absorbed enough heat that the temperature starts rising instead of falling as mentioned earlier.
From this point on you should allow a Rate of Rise of 8 degrees per minute. In this way, it can help you to control your roast, avoid defects, and craft the best possible flavour profile for a coffee.
[Image: Pak Yudhan at Paronworks Roastery in Bali]
First Crack (FC)
Sound is a good indicator of temperature during roasting. There are two temperature thresholds called "cracks" that roasters should listen for. At approximately 196 °C (385 °F), the coffee will emit a cracking sound. This point is referred to as "first crack," marking the beginnings of a "light roast". At first crack, a large amount of the coffee's moisture has been evaporated and the beans will increase in size.
At this point, the burners need to be turned down to very low or even turned off completely. The bean is going through a very rapid loss in moisture and weight; if the burners aren’t reduced, the ends of the bean can start to blacken (tipping) and the surface of the bean can start to scorch.
Roast Development (RD)
Your actions within the Roast Development phase will determine the acidity and body of your coffee roast.
If you choose to roast your coffee beans for a longer time, your body in the cup will increase but you sacrifice acidity. Acidity is usually related to fruity notes, so if you prefer these in your cup then you should reduce the duration of this phase. For a more chocolatey taste profile roast the beans a little longer. In Pak Yudhan's opinion, RD should range between 0 seconds - 2 minutes, depending on what you are trying to get out of your coffee.
Make sure that the temperature remains stable during RD. Aim for a rate of rise by no more than 6℃, but don’t let it drop either. Avoid the temperature from falling by applying just a tad more heat towards the end.
End Heat (EH)
At the end of your Roast Development, you need to turn uo the heat again to bring it up to the temperature that your roast will finish at. A word of warning: due to losing moisture in the roasting process, the beans might get damaged by too much heat.
End Temp (ET)
If by this point your roastery isn't on fire yet, congrats! Time to check whether your beans are done. It's recommended to roast them just a a little darker than expected in case this is your frist roast.
Found this article helpful? Let us know about your roasting experiences in the comments!