How does high airflow strip flavor from the bean? - Page 2

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
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drgary (original poster)
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#11: Post by drgary (original poster) »

Alan, the air is drawn into the roaster underneath the flame and circulating from there and around the perforated drum. Almost the identical roast with that bean is far more flavorful. Perfect or as good as others commenting here? I'm not defending my roasting skills but am asking the general question. An entire roasting session yielded much worse roasts with high airlow in my roaster with other coffees I'd roasted before. BTW the coffee is a very intense and earthy one that I take into start of 2C and brew cool.

Jim and Case, very helpful, thanks.

Ironically while I write about my drum roaster that does best with lower airflow (and probably gradual trimming of heat while maintaining ET), I've been relearning my heat gun/bread machine contraption while troubleshooting an electrical failure on my North. Practice, practice.
Gary
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[creative nickname]
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#12: Post by [creative nickname] »

I do think there is more to it than just effects on ET. When I did my airflow experiments a while back, I tried some with constant air at max. Since the air was high throughout, there was no point at which ET was crashed down by a sudden increase. The roasts still lost some aromatics compared with a more moderate, constant airflow. These were apples-to-apples, all other things as close to equal as possible roasts. I did not notice any tendency to crash or flick with constant high air (rather the opposite, the roast profile was easy to manage), so I can't credit an explanation that the effect of high air is entirely mediated by effects on the ET or profile curve.

I've never tasted a side-by-side run of the same profile run on a drum (with high air) and on a fluidized bed air roaster, so I cannot really comment on whether the latter preserves aromatics that would be lost in the same profile on the drum. If that is true, there is some weird voodoo stuff happening that I do not claim to understand. But I do know what I taste in my own drum, and that is that high air definitely kills off aromas and leaves a roast tasting flatter than it otherwise would.
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archipelago
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#13: Post by archipelago »

I think the question is also worth asking - what is the source of the airflow? Is it fresh air being pulled in across atmospheric burners? Is it recirculated (already hot) air? Is it something else? I think the point about fluidized bed roasters using high airflow of HOT airflow is key. I believe it's likely to do with the roasting environment temperature and resulting differential between the Roasting environment and bean pile temp (greater differential = higher ROR bc enthalpy).

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#14: Post by OldmatefromOZ »

another_jim wrote:I think are partially barking up the wrong tree.
So here's my take: The Am... dropped the ET far and fast in a high thermal mass drum roaster, and that killed the taste. I dropping the ET very slightly in a low thermal mass air roaster, and did the same. Most drum roasters allow for gradual and small drops in the ET without much harm; but basically, any drop in the ET detracts from the taste. Drum roasters require that the heat be checked when approaching the first crack. I get better roasts doing this as gradually as possible. The effect of airflow on the ET varies from machine to machine; but to my mind keeping ET drops minimal is the key.

I think this refusal to futz around frantically with the ET is more important than all the recent ROR-numerology. There is no perfect profile; but there are spoiled roasts from desperately trying to get one.
Thank you :D

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brettpavia
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#15: Post by brettpavia »

This may seem like an unrelated question, but does anybody know of a pictorial resource of roasted beans? While I have the green coffee defects pictures and know what those look like, I have never seen pictures of defects or ideals resulting from the roast.

What cameras we worth investing in for the purpose of recording green and roasted defects?
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hankua
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#16: Post by hankua »

Roast Defects Pictorial:
Coffee Roasting Defects Pictorial

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drgary (original poster)
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#17: Post by drgary (original poster) »

brettpavia wrote:What cameras we worth investing in for the purpose of recording green and roasted defects?
To answer the question it doesn't take much these days. I'm using an iPhone 6S Plus and editing in my Mac's Photos app. OK, back on topic please.
Gary
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