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Whole Leaf Tobacco

Flue-Curing Versus Air Cured

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#1
Could someone please explain why the traditionally air-cured varieties (burley/ Maryland) cannot not simply be flue-cured? It would seem to me a greatly quicker and easier way of doing it.
Is there something inherent in the physiological make-up of burley that means it cannot be simply treated just like brightleaf?
Or is there some desired quality that can only be achieved by the much lower heat and slower drying in the atmosphere?
 

deluxestogie

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#2
...burley/ Maryland...cannot not simply be flue-cured?
Is there something inherent in the physiological make-up of burley that means it cannot be simply treated just like brightleaf?
I've never tried flue-curing a Maryland variety. Flue-cured burley tastes awful and burns poorly. And there is a physiologic reason for that--at least for the white-stem burleys that I've grown.

While a (living) leaf is yellowing in the shed, it is also metabolizing its starches and albuminous proteins. The two separate processes (turning yellow, and breaking down the non-smokable compounds) usually occur simultaneously. Once the leaf is yellow, then dies (on turning brown), both processes are fairly complete.

But that's not the case with white-stem burley, which suffers from a genetic defect in its chlorophyll production. The leaf yellows long before the leaf actually dies, since it already has a head start on the chlorophyll degradation. So the fully yellowed leaf still hasn't died, and hasn't finished the other job. When you flue-cure it, you abort the oxidation of starches and proteins. Thus, unsmokable leaf.

Some Orientals flue-cure well; other don't come out so nice.

The basic idea of flue-curing isn't the color, so much as capturing the high sugar, before it breaks down. Flue-cure varieties have relatively high sugar content to start with. Burley and Maryland both have very low sugar content.

Bob
 

KiwiGrown

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#3
Do you have an Auto advancing thermostat Orson ? I thought you had the same cheap digital stat as me ? Air curing seems much easier to me, baby sitting the stat has caused me a lot of head ache.
 
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#4
Do you have an Auto advancing thermostat Orson ? I thought you had the same cheap digital stat as me ? Air curing seems much easier to me, baby sitting the stat has caused me a lot of head ache.
No, I'm afraid I don't. However, next year I hope to install a programmed control.
Once you've got the flue-chamber sorted out it's a helluva lot easier, less time-consuming and makes a great finished product with brightleaf, the likes of which I certainly haven't achieved in the past with air-curing.
 

KiwiGrown

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#5
What sort of programmable control are you planning on using ?

I can't really find anything for Auto advance.

I'm looking into using a Raspberry Pi (it's a single board computer about the size of a business card) people have used them for meat curing, house climate control etc. Looks like you could repurpose there software for our purpose.
 
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#6
What sort of programmable control are you planning on using ?

I can't really find anything for Auto advance.

I'm looking into using a Raspberry Pi (it's a single board computer about the size of a business card) people have used them for meat curing, house climate control etc. Looks like you could repurpose there software for our purpose.
When I said I was going to install it next year I was cutting myself a bit of slack.
I don't really know what I'll use - I'll be relying on a mate, who tells me it's simple. But that remains to be seen.
Anyway, you're the electrician. When you figure it out I'll be waiting.
At the moment, adjusting the controller manually is no problem for me. I just happen to be around home a lot.
From what I've learned in here lately you certainly wouldn't want a too rigidly controlled program. At the various stages you'd want to be able to easily vary it, where necessary. (eg. Those prescribed first 'two' days of yellowing aren't necessarily always exactly two days, etc).
What I think I want is just something that will handle each day. The most critical element (I believe) are the gradual increments as the temperature climbs up to the next plateau, and then settles there. The next day the next set of increments could be dialled-in.
I think that a totally automated program, where you switched-on and then went awol for six days, would be just a little bit too risky.
 

KiwiGrown

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#7
Controls is almost it's own specialty, most us electricans are capable of wiring it but designing it is another kettle of fish.

I've not much experience in control gear, your brother would have a better idea of what's available but it would probably be quite expensive I would think, what I was thinking of might cost around $100 dollars but it would require a bit of playing around and would be unknown how reliable it would really be.

I don't want full automation I just want to program the 4 stages and you manually switch to each stage with manual override of course.
 
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#8
It would seem to me what you're looking for here is a 'simple' program that would advance the temperature at the rate of 1.0 degree C each hour, then hold indefinitely until manually stopped or programmed for the next set of increases.
(The 1.0 degree per hour approximately conforms to all three gradients on the graph).

Compared to rocket science it should be simple but, then again, I'm no rocket scientist. Next season, okay.

ps. Then there's the humidity factor. But what I've found, so far, that in a well-insulated chamber, it pretty much takes care of itself (with a very small amount of occasional vent-tinkering).
 

KiwiGrown

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#9
Exactly right, I think I've found a program that can do it to and could regulate humidity even if you have dampers with solenoids, all I need is an appropriate sensor, relay and the time to set up the software. Probably a total cost of $100 NZD.
 
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#10
Exactly right, I think I've found a program that can do it to and could regulate humidity even if you have dampers with solenoids, all I need is an appropriate sensor, relay and the time to set up the software. Probably a total cost of $100 NZD.
Well, that sounds like a pretty cheap enhancement, to me.
Especially when you consider it's about the same cost (to NZers) as two ounces of store-bought RYO tobacco.
 
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#11
You can flue cure Maryland and I have a very grainy article on the subject. I flue cured the last of my crop last year and it was as good as the air cured. I did mention it but got no replies or interest. Hope you have good eyes. It basically says that if you follow the same temperatures and times as Virginias you are OK.
Compact curing 1 Maryland.jpg Compact curing 2 Maryland.jpg
 

deluxestogie

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#13
When I enlarge the images of the article, and struggle my way through it, it does not appear to be discussing flue-curing the Maryland.

My understanding of it:
  • Maryland was whole-stalk harvested, and speared onto traditional tobacco sticks.
  • The harvested plants were hung closely packed within a sealed structure.
  • Air was mechanically circulated, and humidity maintained high during yellowing.
  • Temp was raised to 80-90°F after yellowing, allowing the leaf to rapidly dry.
I would consider this simply barn-curing with optimized conditions. The forced air allowed closer than traditional packing within the barn, while 80-90°F is an ideal temperature for both yellowing and drying.

I can't say that Maryland can or can not be flue-cured, since I have not tried it. But your own experience flue-curing Maryland does increase my likelihood of giving that a try, the next time I grow a Maryland variety

Bob

EDIT: One of the apparent goals of this 1983 study was to come up with a process that could be handled from field to finished product using automated machinery.
 

KiwiGrown

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#14
My young eyes can't make this out, maybe I need an optometrist, I must be doing something wrong, Air curing seems easier to me, I just hung out my rustica after a week pile curing, in a dirt floor shed with no door on the back lawn and its all looking nearly ready about 5 weeks later.
 
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#16
Because I still haven't got my head fully around the fundamental difference (as far as it affects the chemical changes in the leaf) between air-drying and flue-curing I am compelled to ask the question;

If a burley, or Maryland leaf has gone through the full run of air-curing and the stem has still not fully dried-off, would it sabotage the whole process if the leaf was 'finished' in a flue-chamber, at 165F (for a period long enough to dry the stem)?
I ran into trouble last year when the weather became damp before the stems had properly dried and the only way I could think of to get around the problem was to remove the stems before fermentation.
 

deluxestogie

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#17
Given your scenario, I would suggest drying the cured burley and Maryland stems at a temperature below 130°F. That should not require much time. In my experience, opening a moist kiln that is at ~125°F, and removing the heated leaf to ambient temperature (~70°F) and air results in both the lamina and leaves rapidly drying, simply because the leaf is much warmer than the air. When I want to bag such leaf with some retained moisture, I have to work fast to prevent it from drying too much.

Bob

EDIT: Another possibility is to stack the cured leaf on a seedling heat mat for a few days, turning it a few times. I've done this a number of times (Knucklehead's suggestion), and been happy with how well it dries stubborn stems.
 
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