what defines tobacco as flue cured?

[DGBAMA]

Is it a specific temperature reached during the process?

Curious because even air curing depends on the same sequence of events. Yellowing-wilting-drying.

So if max temp was held below say 125 deg, and took 8 days instead of 5, would we have simply "speed drying" without the green leaf and the bacca would continue to age naturally?

 

[Knucklehead]

I'm just guessing, but I think the main difference is the temperature required to fix or convert whatever it is to sugars, giving the flue cured it's unique sweetness. I think fixing the sugar is more important than fixing the color, although there may be a relation between the two. That yellow gold sure looks nice, though!

 

[DGBAMA]

I'm just guessing, but I think the main difference is the temperature required to fix or convert whatever it is to sugars, giving the flue cured it's unique sweetness. I think fixing the sugar is more important than fixing the color, although there may be a relation between the two. That yellow gold sure looks nice, though!

Thanks buddy. I Get that part. Just thinking there must be a temp threshold that will dry fast without the effect of flue curing. Curious what that temp would be.

A new process for us little guys. "speed drying" would be very good especially for the northern folk that have plenty oftime to grow but by then poor conditions for "air curing" and do not Want to flue cure.

 

[deluxestogie]

The basic concept of flue-curing is what Boboro is doing: use heat without smoke (it passes out the flue) to accelerate the drying of leaf--essentially just heating a shed or barn. Today, and probably for most of the last century, flue-curing has often been equated with bright-curing, which is a specific process that fixes the sugars, fixes the bright color, and denatures the primary oxidase enzyme (so that the nice color does not vanish rapidly).

So, low temperature flue-curing is still flue-curing, but not bright-curing. And any lemon colored leaf that comes out of a low temp cure will change to brown much more rapidly than leaf from a bright-cure.

If you want leaf with the maximum sugar, and a lasting yellow color (as well as the distinctive "crêpe" texture), the flue-cure must wilt and dry the yellowed leaf rapidly, then quickly go above 150ºF. From an energy cost standpoint, taking stem kill to 165ºF is apparently cheaper than completing stem kill at lower temps over a longer time.

Once I receive a recently published book on the history of flue-curing from Amazon: http://www.amazon.com/dp/1421402866/ (Knucks bated me into buying it, the scoundrel!), I'll either know more details, or go back and correct my misunderstandings.

Bob

 

[deluxestogie]

A new process for us little guys. "speed drying" would be very good especially for the northern folk that have plenty oftime to grow but by then poor conditions for "air curing" and do not Want to flue cure.

In a shed of green leaf, the temp should not go above 104ºF until after the leaf has lost its green. Humidity has to be high enough to allow yellowing before the leaf dries green.

After that (the leaf is now yellow), you can dry it at whatever temp is handy, keeping it below 149ºF. With white stem burleys, the browning (drying) phase should probably be allowed to go more slowly, since it yellows up faster than the other biochemical changes that need to happen.

Bob

 

[DGBAMA]

Mr encyclopedia of tobacco knowledge. Thank you Bob.

So staying at or below 140 should be simply accelerated drying and maintain the natural qualities of the leaf without creating the sugars or fixing the bright color "flue cured" is most known for.

 

[skychaser]

That is an excellent explanation of flue curing Professor Bob.

 

[johnlee1933]

Mr encyclopedia of tobacco knowledge. Thank you Bob.

So staying at or below 140 should be simply accelerated drying and maintain the natural qualities of the leaf without creating the sugars or fixing the bright color "flue cured" is most known for.

Staying below 140 F with enough humidity promotes accelerated yellowing WITHOUT early drying GREEN.

John

 

[DGBAMA]

Staying below 140 F with enough humidity promotes accelerated yellowing WITHOUT early drying GREEN.

John

My idea exactly..... Color cure and dry on an expidited timetable with repeatable results for storage without changing the flavor and aging properties of the leaf as "flue curing" does.

 

[Knucklehead]

I sure like the repeatable results part. Our daily humidity average is going down fast and I'm having to change up my curing procedure to keep from drying green, more leaves per bundle, closer spacing, etc. I will probably need to add moisture soon as I will need to start running the heater at night. It's keeping me on my toes.

 

[DGBAMA]

You and me both. I cut the entire back patch today..will use it to test the theory.

 

[deluxestogie]

104ºF

Taking green leaf above 104ºF (that's 104ºF) will cook (i.e. kill) the leaf, so that it can not naturally yellow. Taking green leaf above 104ºF will ruin the leaf, unless your purpose is to create candela leaf, which retains its chlorophyll.

In summary, taking green leaf above 104ºF is an error, except when making candela (green) wrapper. Keep green leaf below 104ºF for yellowing.

Bob

 

[DGBAMA]

104ºF

Taking green leaf above 104ºF (that's 104ºF) will cook (i.e. kill) the leaf, so that it can not naturally yellow. Taking green leaf above 104ºF will ruin the leaf, unless your purpose is to create candela leaf, which retains its chlorophyll.

In summary, taking green leaf above 104ºF is an error, except when making candela (green) wrapper. Keep green leaf below 104ºF for yellowing.

Bob

Perfect! How many times will I say THANK YOU for sharing your knowledge.

 

[workhorse_01]

I do not leave the 105*F db, 102*F wb mark until all is yellow then advance 1*F per hour until 120* F .

104ºF

Taking green leaf above 104ºF (that's 104ºF) will cook (i.e. kill) the leaf, so that it can not naturally yellow. Taking green leaf above 104ºF will ruin the leaf, unless your purpose is to create candela leaf, which retains its chlorophyll.

In summary, taking green leaf above 104ºF is an error, except when making candela (green) wrapper. Keep green leaf below 104ºF for yellowing.

Bob

 

[deluxestogie]

Staying below 140 F with enough humidity promotes accelerated yellowing WITHOUT early drying GREEN.

It was this post that spurred my outburst about 104ºF being the limit for yellowing. Wet-bulb temp is in the ballpark of leaf surface temperature, so long as the yellowing leaf has internal moisture to evaporate. Ambient moisture reduces the leaf's evaporative cooling, and brings leaf surface temperature closer to the dry-bulb temp.

Bob

 

[bonehead]

i guess i speed dry most of my tobacco because i heat my shed to around onehundred degrees f when it is cool outside. what do you think happens to the tobacco that is already dry when i put new leaf in the shed and raise the temprature and humidity for the for the green tobacco while leaving the old tobacco hanging in the shed? would that help age the tobacco?

 

[AmaxB]

The basic concept of flue-curing is what Boboro is doing: use heat without smoke (it passes out the flue) to accelerate the drying of leaf--essentially just heating a shed or barn. Today, and probably for most of the last century, flue-curing has often been equated with bright-curing, which is a specific process that fixes the sugars, fixes the bright color, and denatures the primary oxidase enzyme (so that the nice color does not vanish rapidly).

So, low temperature flue-curing is still flue-curing, but not bright-curing. And any lemon colored leaf that comes out of a low temp cure will change to brown much more rapidly than leaf from a bright-cure.

If you want leaf with the maximum sugar, and a lasting yellow color (as well as the distinctive "crêpe" texture), the flue-cure must wilt and dry the yellowed leaf rapidly, then quickly go above 150ºF. From an energy cost standpoint, taking stem kill to 165ºF is apparently cheaper than completing stem kill at lower temps over a longer time.

Once I receive a recently published book on the history of flue-curing from Amazon: http://www.amazon.com/dp/1421402866/ (Knucks bated me into buying it, the scoundrel!), I'll either know more details, or go back and correct my misunderstandings.

Bob

Thank You!!

 

[workhorse_01]

I read that too. I knew what he meant, but he said something different. A new to flue person would cure a lot of green leaf at 140*F.

It was this post that spurred my outburst about 104ºF being the limit for yellowing. Wet-bulb temp is in the ballpark of leaf surface temperature, so long as the yellowing leaf has internal moisture to evaporate. Ambient moisture reduces the leaf's evaporative cooling, and brings leaf surface temperature closer to the dry-bulb temp.

Bob

 

[Mad Oshea]

I live in the desert here and never had a problem. I do however use plastic bags to cure sometimes.(black and set in the sun) But however to flue cure I use a 55 gal barrel and a pot of burnt wood chips under a convection top watching the heat and humid. I can pm any plans if You want. Just My way to do it.