What exactly is a roast profile?

What exactly is a roast profile?

David Kemble

There a lots of terms banded around in the coffee trade, particularly in the speciality coffee trade. I think very often we are guilty of assuming that our customers know just as much as we do.

I have been a coffee lover for as long as I care to remember but had you have asked me what the term 'roast profile' meant before I started roasting for myself I probably would've given you an answer with a fair amount of mumbling

I am going to try and break down the process of roasting today and demystify what we mean by the various terms we roasters band around when talking about roasting.

A coffee roasting cycle is made up of the following stages:

  • Charge - This is what we call the moment when we drop the green coffee in to the roast drum.
  • Turning Point - When we add the cold coffee to the hot roaster, the green coffee reduces the temperature of the roaster. Turning Point is the point at which the roaster and bean mass equalise in temperature and the temperature starts to climb upward.
  • Drying Phase - This is the period after Turning Point when the beans give off lots of moisture and turn from green, to a straw like yellow and then on to browning.
  • First Crack - When the beans reach a certain temperature they suddenly rapidly expand and give off lots of energy and gas. They make a cracking noise much like popcorn.
  • Second Crack - This phase of a roast comes a little after first crack and sounds similar but is of a more high pitch energetic popping sound. We do not roast our coffee this far.
  • Drop - This is when the coffee is dropped from the roasting drum in to the cooling tray and is the end of the roasting cycle. This can be anywhere from the start of first crack to after second crack.

Nowadays most coffee roasters are linked to a computer and some very clever software. This software constantly measures various parameters coming from sensors in the coffee roaster and plots the data to a graph like the one shown in the above picture. What is the point you might say? Well it is for consistency. If we can plot the time and temperature of a coffee during its roast cycle it means we can repeat it and get the same result each time. Equally if we roast some coffee and we are not happy with the outcome or think we can improve, we can look at the graph and decide how and what we may like to change.

This data set is what is referred to as a roast profile. For us it is unique to each coffee we roast and is much like a chefs recipe and enables us to achieve a consistent quality result. It doesn't matter which roast master is in charge that day, so long as they have the profile they are able to produce the same result time and time again.


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