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Journal #2 - Underdevelopment

In this chapter of the never ending quest to roast amazing coffee, I've been thinking a lot of about underdevelopment.

And as a roaster who is aiming for all sorts of light modern coffee, underdevelopment tends to come creeping around often.

I define light roasted specialty coffee as having the most origin/coffee specific flavor and the least roasted flavor.

Modern specialty light roasted coffee is full of juiciness, sweetness, great acidity, and has no roast defects. It is floral and syrupy and leaves a pleasant taste in your mouth. It is interesting enough to drink multiple cups of. In terms of sweetness - it can be either white refined sugar or move into the molasses panela range of more unrefined sugarcane products.

Unfortunately, underdevelopment shows up so much in these coffees, both ones I taste from other roasters, AND EVEN MY OWN. There I said it. How can I get better if I am not willing to admit my own (roast) issues.

These are the underdeveloped notes that I generally taste. And I have kind of grouped them together in my own mind.



Citrus Rind

Sometimes I taste something akin to celery in the coffee as well, but that goes with vegetal probably.

Have you ever sucked on a coffee bean before? Or steeped unground light roasted coffee in water for like 15 minutes and just drank it? It is a taste that I can't categorize or explain, but it is something that I taste in underextracted, underdeveloped coffee all the time.

So how do we get rid of these negative notes in coffee? Well, most roasters would just tell you to roast darker. That is so vague and quite frankly isnt good enough for me. Especially when I have had light coffees out there that dont have any taste of underdevelopment.

My first hint at the culprit is inner bean development during the first phase of roasting. This is caused by the total thermal energy put into the coffee during the first phase. From my own understanding of coffee roasting: total thermal energy in the first phase of coffee roasting can be deduced by understanding 3 keys things.

  1. Length of the first phase or the time it takes to turn from green to fully yellow
  2. Peak ROR
  3. Area under the curve during the first phase. In cropster it will be called Roast Area Index

If you have too long of a first phase, you will most likely taste underdeveloped notes because you are not putting adequate energy into your coffee and the best chemical changes needed for coffee to taste great won't happen. If you have too fast of a first phase, you will most likely taste underdeveloped notes because you will be roasting the outside too quickly and not giving physics magic enough time to transfer heat into the interior of the bean and create all the chemical changes needed for coffee to taste great.

Peak ROR (Rate of Rise) will tell us the thermal momentum being applied to the coffee when it gets into the roaster and starts to heat up.

Theoretically, if we try different roasts with different heat applications in the first phase, we can pick the best one out and start refining each of these aspects to better understand how to have the coffee taste the best. Say we taste the coffees and find the profile with minimal underdeveloped notes, we can change the length of time the first phase took, while keeping the roast area index the same. This theoretically (if everything else is the same) allow for a similar inner bean development with difference in perceived acidity.

I've recently read someone's blog saying that this is wrong. But I am still holding on to it for now until I find another baseline way of doing things and manipulating the coffee.