rival81 wrote:
Drying phase At this stage, i've got heat on a medium setting. My temp control is a dial with numbers, so i have completely variable control at all times during the roast. Temperature in the bean mass generally reaches 70 degrees after 1 minute, 100 degrees after 3.5 minutes. This is the initial drying phase. Once i reach 100 degrees i generally back off the heat input just a little bit. It's important to keep a very close eye on the rate of temperature increase. I generally do not need to make any further adjustments until 1 minute before first crack. That is at the 9 minute mark around 185 degrees, i reduce heat further to slow the temperature increase to 4 - 5 degrees per minute.
When monitoring your roast in the early stages you need to look at your turning point - the moment when the rate of temp drop has "bottomed out" and the beans start to heat up and your initial ramp is underway. Turning point (TP) ranges vary depending upon the roasting device, charge temp, bean mass & type, energy source (heat) and the environmental conditions such as ambient temp of beans, etc. For roast devices that use some forms of conduction and convection, e.g. a drum, etc. you should be trying to look for a turning point between 2:30 and at perhaps 3:00 mins. I find TP calcs a highly valuable indicator on whether I've worked out the correct ratios of green kg's, charge temp, energy applied, drum speed and airflow. So important is this for me that when roasting a new bean I will do some very quick sums in my head based on experience and try to run ahead of the profile curve to predict (or visualize) how the bean will behave in the chamber during the execution of the roast. It's a particularly fun game for those times when you are shackled to the roaster for 11hrs straight ???. Just like a surfer getting into the precise position for takeoff on a classic wave, or a golfer seeking to position the ball in a certain zone for the next shot, the TP can be a very useful gauge to "SETUP" the roast so that you have the right variables in play for the important temp ramps - making it that much easier to control and manage the roast, rather than respond or react to the roast. Hot air roasters behave a little differently in respect to TP's but this is still an influential checkpoint on the journey to that perfect batch !
