Preheat and cooling down process in coffee roasting are small but important procedures. One of them is the start of coffee roasting: to give a suitable temperature of the drum, while the other one is the last part of roasting: to preserve the coffee flavour and bring the sudden change of the bean temperature. It sounds very interesting, let us talk about it a little bit more today!
About Pre-heat and drum temperature setting
When we are preparing to roast the coffee, we need to weigh the green beans and loaded it into the hopper. Although they are ready to be dropped into the drum, sometimes they may have to wait a while. Why is that?
It’s because the roaster has to be preheated to a set temperature and reached the drum set temperature before we drop the beans into the drum. Just like cooking, we would never put a steak into a cold pan. If we pre-heat the oven before we bake a cake, the cake can develop better when it is in the oven. Coffee Roasting shares the similar principle to cooking: it definitely need a preheat procedure.
According to the different characteristic of the green beans, the weather, moisture, how much green beans we roast, etc., the preheat and drum set temperature will be different. And the preheated process will help a lot in creating the roasting profile.
The key of dropping the bean: Cooling down process
No matter the green beans, the beans that are being roasted, or the roasted coffee beans, they are both very easy to affected by temperature. The beans which are being roasting will have physical and chemical change when there is a change in temperature. Even when we are about to finish roasting, we still need to pay attention to the bean temperature.
Cooling down is an important process during Coffee Roasting. When the coffee beans drop out of the drum, it can reach at least 210 or above degree Celsius. Therefore the beans can keep cooking themselves in the cooling tray if the cooling process is not fast enough. The malty or rye-bread flavour will be created and that is the flavour which a roaster should avoid.
Usually, there are mainly two ways to cool down the beans: by air or by water. In Coffee Roasters Asia, we are using the air- cooled method. There is a cooler under the cooling tray and Mixer in the cooling tray. When we are about to drop the bean out, we will need to press the button and make them operate. These tools help to cool down the beans immediately. It’s quick and efficient.
The Cooling down process will take 4 minutes usually. When it is finish, we need to put the beans into a sealed bag in order to keep its freshness.