an overview of coffee roasting, 23 August 2026.

This is basically a recap of my coffee things learned from my past coffee career.

data collection during roasting to understand solubility of volatile organic compounds (VOC)

- charge temp or preheat temp

- turning point

- drying phase

- mailard phase

- rate of rise

- first crack

- drop temp

- development time

- weight loss, initial moisture.

1. charge temperature

- the initial temperature the roasting chamber maintains at a 0-3 ROR to allow a consistent roasting. 

the effects of charge temp in my opinion needs to do to work alongside in-drum moisture level as well. I feel if the internal has a higher moisture at that temperature, the coffee will still have a different drying compared to a lower moisture in-drum with the same charge temp. charge temp affects your turning point as well. it mainly provides an initial negative energy pressure directing inwards to the bean. a higher charge temo has a higher amount of energy for the coffee bean to soak in, now i want to try 230-240c charge temps on the rubasse because the rubasse doesnt have hot air and conductive pwoer to scorch the beans exterior. 

2. turning point

- some say its when the bean and the environment starts to equalize in temperature. i dont know too much about this, maybe just a data point at the moment. energy momentum means an accelerating ROR, an earlier turning point signals a higher momentum, faster drying incoming.

3. drying phase

- the drying phase technically spans throughout the moment when green coffee enters the chamber up until a fragrant baked goods smell pops up, signaling the start of mailard, the end of dry phase.

so far the coffees i enjoy, inga aponte, alo main station, sidama g2 field blend, taste quite solid with a short dryphase, means a high heat control. Xavi tried a slow drying phase from a low charge temp on a kenya, it turns out quite nice, long aftertaste. throughout this phase, the coffee bean is constantly losing moisture and gaining heat energy and internal pressure.

4. mailard phase

- signal by visual and smell cues. a color change to yellow and golden, and a fragrant baked goods smell.

in this stage, one can tune the length of a mailard phase to compare the effects of loger vs shorter, a longer mailard will be a longer roast time, a later first crack. a shorter mailard would mean a shorter total roast time, and a faster first crack.

5. rate of rise

- or ROR, is a signal telling you thr heat momentum of the roast, giving you an idea of how is the roast performing, like telling you how fast you are driving. I would expand into a flat ROR vs high peak ROR, vs slow cascade ROR to experiment in detail the effects.

6. first crack

- upon reaching first crack, the moisture increases as beans literally gain so much internal pressure that is explodes and turns inside out, moistuire is released. that is why  want to try no crack, or a soft crack.

it is also where the coffee starts development time, used to measure a length of development the bean goes through after cracking. the bean becomes very fragile and prone to over roasting as the structure is immeadiately broken and the internal compounds are immeadiately exposed to the heat source. during first crach, the coffee, to me, often smells: fresh fruit acidity, floral, caramel sweetness, and i prefer deciding drop temp and time through this process of constantly smelling the coffee to see its constantly changing state, in natural coffees, i often drop them abit after smelling the ideal fruity profile. while for washed coffees, i often prolong 10-30 seconds later than naturals, as i feel it takes more time to have chemical exchange even when the floral notes are already present. 

7. drop temp

- drop temp and drop time is crucial to maintain roast consistency. a higher drop temp means more heat, more transformation, a later drop time also means a longer development, which makes me curious of the effects that i want to experiment on drop temp vs drop time. generally 1-2c difference is ok, and 1-5 seconds in time is ok.

8. weight loss vs initial moisture level.

- robhoos said he usually roasts 2% above his initial moisture level for consistency and respect to relative profiles of green coffee.  a higher moisture content or water activity points to a more unpredictable green coffee, while a stable or lower water activity coffee will be more shelf stable. generally a higher water content would mean a need for a stronger dry phase and the opposite as well. a lower moisture level would be more delicate as well in the drum.

on brewing as calibration

- assessing the coffee through solubility understanding, with individual brewing approach, what is easily extracted into the coffee? ie. flavour, acidity, sweetness, mouthfeel. corelate with the coffees inherent information, is this a wshed? a natural? an advanced processing?

- an ethiopian natural usually offers a big range of aromatics and flavour, along with a fruiter perceived sweetness, its setbacks might be a hard point to balance mouthfeel and sweetness with aromatics. the aromatics might offer too much while sweetness and mouthfeel might undermine the balance.

-  honduras parainema washed i had roasted on a stronghold, ovidio gomez. a high clarity in clean floral, herbaceous, tea notes. usual brewing approach would then overextract the end notes leading into a tremendous amount of astringency and roasty notes. i approach the coffee with 85c temperature, and a 1:10 brewing ratio, with a medium coarse grind, to ensure the viscocity, the body, the mouthfeel is well balanced with the delicate white floral, dried fruit,white tea aromatics. 

- there is no one way to approach a coffee, i believe a coffee that is well taken care of, can display different profiles that are equally interesting through different approaches.

on roasting

- green bean with high moisture, decrease moisture in coffee bean, coffee bean dry, and start to caramelize, chemical transformation from green coffee to roasted.

- hot air has less roasted bright notes, but more expression of coffee

- gas drum roaster might have more structure and definition of layers

- infrared roaster like stronghold and loring cooks the bean from inside, almost no charring or roasty notes will occur, but the trick to balance in and out is hard, coffee comes out often clean, which pushes towards a good espresso roaster, solid flavour and aroma, defined character.