Even if you have set up your machine perfectly and developed an optimal between-batch protocol, it’s impossible to avoid small variations between batches. Coffee is a variable, organic product, and small changes in atmospheric conditions, gas pressure at the burner, or even the voltage in the electricity supply can influence the development of a roast curve. As such, it’s very difficult to precisely repeat roasts using only manual controls.
When using only the manual controls on a roaster, it can be hard to replicate roasts precisely.
Automation has the potential to enable much more consistent results in roasting, but many of the available automation systems fall short in one way or another. In the early days of roasting automation, the sudden, extreme gas and airflow changes that machines would apply in an attempt to follow a roast curve would rarely give satisfactory results. Newer systems offer partial automation, which can help with consistency or reduce labour costs. As automation continues to develop, fully autonomous roasting will become more common, allowing roasters to spend more time evaluating their coffees and analysing their curves instead of standing at the machine, making manual adustments.
In general, three types of automation are available to roasters today:
Semi-automatic Roasting
Some roasters have the capability to automatically follow a ‘recipe’ of burner and airflow settings to replicate a roast automatically. The operator still has to develop the recipe manually in order to achieve a desired roast curve, and the roasting machine simply follows those instructions in order to replicate them. The recipe may indicate when to make gas changes by roast time, or each gas change may be triggered when the beans reach a certain temperature.
Scott describes this type of control as ‘semi-automatic’ roasting. Examples include “Burner Recipes” on Lorings and the PILOT control system available from Probat. Cropster can also control some roasters with its ‘Control and Replay functionality.
This type of control is ‘semi-automatic’ in that the machine adjusts the gas settings during the roast,