Saturday, January 21, 2012

Bean Temp. Rate of Rise **BT RoR** an approach to roasting and analysis

I've been interested in BT RoR for several years. First, to consider a different way to drive a roast and second, having something more detailed for post roast analysis.
Through the efforts of the amateur/home roaster community, various types of monitoring and also controlling systems have been developed over the past couple years. (see posts below for more info.)

As amateur home roasters we tend to play with small amounts of various lots of different beans. Our stash is not a "production" stash. It's collection of a couple/few lbs of various great coffees. We can't mess around with several roasts of a bean trying to nail the preferred roast profile. But instead buy known great lots and learn as much as we can about them before we roast.  Then create a profile and try to nail it the first time. If we spend big bucks on a couple batches worth of a Gesha coffee to roast, the pressure is on. Beans I get from Sweet Marias have Tom's very detailed descriptions and info. Pretty much all a roaster needs to know about a lot to develop a good approach to the roast.

Having an approach and driving dead center with how the beans are actually reacting on the first roast is the next trick. This is where the addition of live BT RoR readings are useful. The trend of the bean temp rate of rise allows a quicker heads up that changes need to be made(factoring in ET/MET,Time). RoR allows easy calculations of upcoming arrival times for key points during the roast. The focus needs to be on the senses sight, smell and sounds.  With quick glances at BT RoR needed changes can be considered and made faster to be keep that focus on sensory monitoring. If the beans are telling you they could stand more heat transfer and your looking for speed in that segment for hoped cup results, than the quicker you can realize that and make adjustments the better.
green line is BT RoR (vertical readings without the 0 = degrees rise f/min.)
Red-BT f
Yellow-ET f
Tan -Voltage to electric element (juice)
The list on right are most recent readings per 5 sec.
.csv file per sec. of readings saved

BT RoR graphing substantially adds detail to post roast analysis. It is basically what I try to gather together in my mind by looking at a typical time/temp ET and BT graph. Instead the BT RoR line becomes the focus graph showing how the beans reacted to the other conditions shown. It's what completes this different approach to roasting. It's been an enlightening experience that does take some time to get used to.  Adding  BT RoR can also really help when wanting to communicate a roast profile and to transfer profiles between 2 different roasters.

 BT RoR readings have been used in various ways in the recent past. It's when combined with the graphing ability that a complete approach shift can be considered. ET RoC monitoring ET rate of change may be useful for high heat mass roasters with a proper TC placement.

If the 1st. World Roasting Championship could add BT RoR graphing of the roasts it sure would make it more interesting in analysis.