How to solve uneven color


#1

I roasted Colombian washed coffee yesterday, and saw which might be a defect.

The surface of the beans didn’t have even color but tiger skin like unevenness.

Also the crack was quite bright but when ground, the color wasnt that light and it was more like medium roast.

In summary

  • the bean surface color was uneven. Is this because i applied too much heat in the beginning?
  • Although the overall color was darker than i expected, the crack was pretty light colored and when tasted it had a bit of baked flavors.

How can I solve this problem? So that the outside color gets even and lighter but it does not have any baked flavors?


#2

I can think of three factors that can mitigate the outside bean texture, and using these factors together or individually can give you the boost the beans need. But none of it matters if the roast smells great and tastes how you like in the cup.

My observations so far for the physical phenomena is that the outside cells swell and puff out, the lighter part is actually more cooked than those darker parts. Once the bean is smooth the ending temp has the most significant factor on the bean color and can by altering adding energy to the beans in the yellow to brown phase. Beans adversity to taking on heat is its density and moisture content so an Ethiopian high grown is much easier taking on heat. A low grown Brazil would be it’s opposite but funnily enough if you have a Guatemalan which is spongy yet has a lot of water this requires a lot more energy in the beginning. So the bean characteristics are always the basis for building the profile.

  1. Increase speed, via ROR during yellow to brown. This ramp up creates enough energy potential in the bean to expand. For me this is roughly the range between 360F-415F which yellow can start, to 420F-455F where brown starts (Based in Marshal Etheo style profile). Sidenote*

  2. Increasing conduction (lowering fan).

  3. High sustained inlet temp will inevitably push the beans though the stages so the beans can build this momentum.

*For all beans; basing the color phases on time duration is a decent way to build a profile. Meaning input temp is based on how long it takes for the beans to go through green/yellow/brown/1C+dev/2C+dev.


#3

I’ll try my best.
So you mean that i should introduce faster and more heat before first crack?
Do Colombian beans usually need more heat applied compared to Ethiopian high grown beans?


#4

Generally speaking yes you want to introduce more energy into the beans, not necessarily more heat. Because if you add too much heat than you can get tipping/baked roasts. So instead of adding heat you can lengthen the segment or increase fan which will speed up moisture removal. But everything is based on a weighted scale when it come to roasting so trying out ideas and tasting the results will give you your answer. Taking notes will help speed up this process.

Columbian beans usually do need more heat but if the altitude/varietal/processing are the same than no, it all depends. Roasting and cupping are pretty much the only way to know for sure where to go.