Coffee roasting, whether 100g or 100kg batches, often involves roasting multiple batches, one after another. Regardless of the size of the roaster, consistent profile following requires starting every roast in the same thermal state. That is, the roaster must be reset to a consistent thermal state otherwise it will heat the beans differently for every batch, resulting in flavour and development differences between batches.
In a conventional drum roaster the roast cycle is started with pre-heat. Beans are added only when pre-heat is complete and the drum is hot. Heat is transferred from the drum to the beans. Consistent profile following is dependent on consistent transfer of heat from the drum. For this reason, a specific protocol must be followed between batches. This is not just done to return the roaster to the same pre-heat temperature, but is done to return the entire roasting system to the same amount and distribution of stored heat. A specific sequence of heating and cooling is often used to ensure consistency. This is an essential part of the ‘between batch protocol’ or BBP.
The Kaffelogic Nano 7 is not a conventional drum roaster, but this does not mean that it can operate without a BBP.
The Kaffelogic roast chamber has ultra low thermal mass. The roast starts from ambient temperature with beans in the chamber. Hot air is blown into the chamber. Heat is transferred from the air to the beans, with only a small amount of heat being transferred to the metal of the roast chamber. Consistent roasts are achieved by returning the roast chamber to ambient temperature between batches. This ensures the ratio of heat going to beans and metal remains consistent from batch to batch.
The Kaffelogic BBP starts when the roast ends and cool down begins. Cool down is therefore the first part of the BBP. It takes place with the roasted beans still in the roast chamber.
The initial part of cool down quenches the roast, stopping development and locking in the flavour. Initial cooling is very rapid. That is followed by a longer period of cooling which first brings the beans to a temperature at which they can be handled and then resets the stored heat of the entire roasting system. Cool down continues until thermal equilibrium is reached equivalent to the whole system being at ambient temperature.
Note
If you just want the beans fast you can stop cool down as early as you like. Press ▶ then -. But if you are intending to roast back-to-back batches you must have the full BBP: let cool down run until the roaster stops it automatically. (BTW, don’t turn the roaster off between batches. As part of the BBP it measures ambient temperature and this measurement affects the next batch. When you turn the roaster off this disrupts the measurement of ambient temperature for the next batch.)
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