Roasting with minimal equipment: Sight, sound, smell & a simple temp probe.
The 3 impt phases of coffee are the drying phase (the beans change colour from green to yellow), the browning phase, development phase
Roasting coffee with only drum temperature readings involves a manual process using a timer and notebook to track time, temperature, and color changes, which you can use to manually adjust heat settings and control the roast.
This method requires careful observation to identify the turning point, monitor the rate of rise (ROR), and note when to make adjustments to hit key milestones like first crack and the final drop temperature. While challenging, it offers a deeper understanding of roasting principles and prepares you for situations where automated data is unavailable.
Roasting steps
1. Preheat and charge:
up the drum to a consistent temperature and preheat the roaster. Note this charge temperature when you add the beans.
2. Monitor the temperature drop: As the cold beans are added, the drum temperature will drop significantly. Use your notes to track the "turning point" where the temperature stops declining and begins to rise again.
3.Track the rate of rise (ROR): Use a timer to take temperature readings every 30 seconds.
Manually calculate the ROR by doubling the difference between consecutive readings to gauge the speed of the roast.
4.
During the drying phase observe bean color and adjust heat:
Watch the beans change from green to yellow.
You may smell "hay" -> "grass" -> "yeast or dough".
The bean will also start to swell in size. As the beans change size and shape they will
tumble differently.
Adjust your gas setting to control the ROR. For example, slow down the roast as you approach first crack by reducing the heat.
You should aim to get the dry phase to last 4 - 5 mins. No shorter.
Thus being able to control the temp is useful. not rushing this phase will minimise roast defects & allow the heat to penetrate to the centre of the seed.
5. browning phase. Use your nose & eyes.
This phase is where all the flavour development comes from. So don't rush it.
Firstly make sure there is no green coloured beans left. Everything should be yellow.
The colour now changes : Yellow -> brown
The smell changes from a yeasty-doughy smell to sweetness. Also smell "baked goods" ...
like a berry or apple pie crust, cinnamon, spice
We are caramelizing the beans. Acidity gives off aromas of fruit.
6. First crack: Listen for the audible "first crack" and make a note of the time and temperature.
This is the end of the browning phase.
You may want to aim for a lower ROR at this stage, such as \(10^{\circ }C\) per minute.
7. development phase: Continue monitoring the ROR and bean color.
Continue smelling the coffee after 1st crack (every 15 secs).
Adjust heat as needed to control the roast and prevent it from moving too fast.
8. Drop the roast: Decide on a final drum temperature to drop the coffee,
and activate the cooling fan at the same time.
The time you drop your beans is a individual decision ... could be a specific temp,
or a percentage of the total time.
Key considerations
Consistency is crucial: For this manual method to be consistent, try to keep other variables like drum speed and airflow the same for each roast.
Match roasts: Knowing the pre-roast drum temperature can be vital for achieving consistency between batches, especially for the first roast of the day.
Be prepared for variation: Each roaster and thermocouple installation will have unique readings, so expect variation. The key is to develop a consistent process that works for your specific equipment.
Focus on the ROR: A smooth and controlled ROR is the most critical aspect of a balanced roast. Don't rely on the time to drop; use color and the ROR as your primary indicators
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