Diedrich IR-5 Analysis by Doris Garrido
Roasting a decaffeinated coffee is always a challenge, and I will always hesitate at the beginning with gas application since sometimes coffee will run fast at the beginning of the first crack. This is because of the decaffeination treatment that the coffee has gone through, making the loss of moisture faster than other coffees.
On the green grading, Peru Norandino, our new Decaf, has marked average density and moisture content, which made me decide to start low on charge temperature, and pay extra attention to the turning point to take further decisions for the rest of the roast.
To start I used a batch size of 5.5lbs and I planned to roast on the 5-kilo Diedrich roaster. I set the charge temperature at 411F.
For the gas movements, I started with 30% at the beginning of the roast then 100% before the first minute, and lowered to 70% after I had passed the turning point. The turning point (1:24/182’F) let me know that coffee was receiving the heat fast and I wanted to slow down the drying stage by lowering gas.
After the color change I set the gas at 30%. From there I got a safe rate of change to finish the roast. In general, for the gas adjustment, I just add the push at the beginning and lower the heat until the end of roast.
As for air, I started the roast with 50% air from the beginning and left it for the first 3 minutes. I was not sure if I had applied excessive heat at charging, and the air may help to soften the stress on the coffee at the beginning as is needed. I use air again when the coffee starts cracking, this time to push the smoke out of the drum.
Things to notice on decaf. Because of its dark brown color, catching color change tends to be challenging. The way I caught it here was by smell, I looked for the hay aroma and ended marking at 310F, I was also able to notice small changes in color.
Getting into the last stage of the roasting, I got 14F/minute rate of change at first crack. This left me with a soft cracking, and I called it at 398F.
I gave this coffee a long development time at nearly two minutes, and dropped it at 399F. I ended the roast with 64 Colortrack (whole bean) and 58 Colortrack ground. I was worried that with the development, the coffee would taste ashy, but in the cup the coffee performed cleanly with notes of apricot, black tea, brown sugar, chocolate mousse, graham cracker, grapefruit, hazelnut, lemon-lime, marjoram, peach, and s’mores. This Peru has won its position on our menu and will be served as our new decaf espresso offering here at The Crown!
