High ROR at start of roast in a fluid bed

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
Jimfoto
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#1: Post by Jimfoto »

I roast on a FR800 with a Razzo chamber and chaff lid mod. All of my roasts spend the first minute or so at a very high ROR. This is on fan 9 heat 1. I've always attributed this to it being a fluid bed and doing a cold start. As the roaster heats up and the probe measures the heating air the ROR calculated is high. My DE is always around 3'30" or so. Am I missing something here? How do I start the roast at a lower ROR when the roaster has no lower heat available?




Pressino
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#2: Post by Pressino »

How do I start the roast at a lower ROR when the roaster has no lower heat available?

You could try running the roaster empty for a while to heat up before charging it or change the charge mass. However, since you are measuring bean temperature ROR, you are always going to have a relatively higher ROR at the beginning of the roast when you charge the roaster with room temperature beans. By changing the charge weight or preheating the machine before charging, you could maybe tweak the ROR a bit, but how much will be limited by the fundamental laws of thermodynamics.

You said you have no lower heat setting, but can you change fan speed?

Jimfoto (original poster)
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#3: Post by Jimfoto (original poster) »

The fan speed is on high which is the lowest heat producing setting. Preheating the machine will produce a lower ROR graph in Artisan but should actually increase the real bean ROR as they're being dropped into a hotter chamber. That's why I've ignored the first minute or so of the graph.

A larger charge weight is interesting as that should actually decrease the initial ROR because of the larger mass. That's something to consider.

SutterMill
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#4: Post by SutterMill »

Jimfoto wrote:A larger charge weight is interesting as that should actually decrease the initial ROR because of the larger mass. That's something to consider.
Its a double edged sword. The larger mass will require more heat, but it also slows down air going through the mass so the roaster is hotter at the same settings.

If you have any cheap beans its easy to try. Just do 180g roast and a 260g roast 30 min later using the same settings. With 300g roasts can I run out of headroom with the fan power getting to hot when I trying to keep beans out of the chaf collector

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drgary
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#5: Post by drgary »

Since no one has asked this yet, how do your roasts taste? Are you happy with your results?

As far as BT ROR goes at the very start of the roast, that's when the beans are full of moisture and there are few chemical reactions happening. You're essentially building pressure inside the bean and heating it through.
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LBIespresso
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#6: Post by LBIespresso »

I won't be the least bit surprised to find that my thinking is backwards in another 5 or 10 years but isn't it generally accepted that, aside from scorching or other roast defects, the impact the roaster operator has on the coffee is the greatest in the end of the roast and the least in the beginning of a roast?

I have played with charge temp and soaking but never with the intent of achieving goals for the beginning of the roast. I have only done that to help me steer the end of the roast.

Am I wrong to say that the early data in a roast is not worth worrying about unless you are using it to help change something in the middle or end?
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randytsuch
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#7: Post by randytsuch »

A couple of years ago I was roasting with a modded popcorn pumper, and my profiles looked very similar.

ROR jumped off the chart for the first min or two, then came down to more reasonable levels.

I was using the PID function in Artisan to control my pumper. I divided the roasts up with different RORs during the roast. To progressively lower ROR as the roast progressed. I played with my profiles to try to lower that initial high ROR, but never succeeded.

In the end, I was happy with the roasts so I stopped worrying about it.

Later I moved to a Stir Crazy Turbo Oven setup to increase batch size.

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LBIespresso
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#8: Post by LBIespresso »

LBIespresso wrote:I won't be the least bit surprised to find that my thinking is backwards in another 5 or 10 years but isn't it generally accepted that, aside from scorching or other roast defects, the impact the roaster operator has on the coffee is the greatest in the end of the roast and the least in the beginning of a roast?
Lol I just did 2 different roasts where the main difference was getting to yellow 1 minute faster and keeping the other phases the same with one roast was dropped 1 minute shorter. The faster roast was more developed, complex, and had baking spice notes. The longer roast was still very good (thanks to the farmer not me) but was punchier and more stone fruit dominant but less complex.

So I tested it with another green and basically the same results. Go figure, not only was I wrong but I was wrong about how long it would take me to be proven wrong.

These roasts were done on the Ikawa Pro. I do think the high ROR at the start is the nature of a fluid bed/convection heat. Is it because all of that extra airflow is hitting the probe and convective heat transfers faster?
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Milligan
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#9: Post by Milligan »

The main objective of the beginning of the roast is to not introduce roast defects (mostly tipping) and set up the momentum of the roast for whatever your roast objectives are. Since this is an air thread then we can focus on fluid bed and/or high convection methods. Hoos wrote a small booklet on tipping and found results similar to my experience that high convective heat transfer at the beginning of the roast can introduce tipping. I had a hard time introducing tipping into beans when I owned my Ikawa even if I pushed hard. This may be due to the smaller batch size providing a more even application of heat at an overall lower energy level (perhaps lower heat flux at the initial application boundary, ie the first beans to be hit with the heat in the bean mass where heat is the highest.) On my Stronghold I can introduce tipping quite easily with high initial hot air (this is not a fluid bed roaster, but a hybrid.) I was able to tip some beans on my USRC (gas drum) with high initial air flow and heat application leading up to charge.

Getting through dry and having a high RoR sets your roast up for a quick Maillard. Typically when roasting light or nordic light, an energetic Maillard leading to first crack is beneficial to induce a closely spaced cracking of the beans so even development happens faster. For example, casually cruising up to first crack at 8mins with a 14F/min RoR at first crack will likely be a 2min or so development time before most of the "cracking" is finished. Racing to FC in 6:30-7min with a 20F/min RoR (controlled) may get the cracking finished in 1min, for example. This is all dependent on the coffees, processing and such.

Some go by the philosophy that you go as fast through dry as the beans can take without introducing roast defects. This can be done faster on fluid bed. As with anything, the specifics depend on your machine, environment, goals and coffee.

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LBIespresso
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#10: Post by LBIespresso »

Milligan wrote: Getting through dry and having a high RoR sets your roast up for a quick Maillard. Typically when roasting light or nordic light, an energetic Maillard leading to first crack is beneficial to induce a closely spaced cracking of the beans so even development happens faster. For example, casually cruising up to first crack at 8mins with a 14F/min RoR at first crack will likely be a 2min or so development time before most of the "cracking" is finished. Racing to FC in 6:30-7min with a 20F/min RoR (controlled) may get the cracking finished in 1min, for example. This is all dependent on the coffees, processing and such.
This would explain the faster roast having a more developed profile even though it had the same amount of development time and was even dropped a few degrees earlier.

Absolute development time, DTR, FC to FCE: All of these are important. Roasting is a never ending puzzle.
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