After sun curing (or rajangan curing), what should I do to keep them sweet ?

[Charly]

From what I have read about flue curing, the fast drying keep them yellow and the high temperature (165°F or 72°C) kills the first enzyme so they save a lot of their sugar.

This makes me wonder : if I manage to air/sun cure (or rajangan cure) some leaves and end up with nice yellow/orange/red leaves, should I put these leaves in my oven at 165°F to kill the first enzyme too if I want them to stay sweet ?

This year, we had a really hot and dry weather, and some of my virginias air cured with yellow/orange color (but only some of them sadly... the others turned brown), so I would like them to stay as sweet as possible

 

[ChinaVoodoo]

I've never thought of that. I can't see it harming to have the tobacco at such a temperature. Try it and report back.

 

[deluxestogie]

Most sun-cured Oriental tobaccos are not further treated in any way. They are allowed to slowly "ferment" in stacked bales at the warehouse. My own sun-cured Orientals do go into the kiln afterwards (max 128°F), and this leads to some visible and taste alteration. After such treatment, the leaf does continue to age very gradually. I have some sun-cured then kilned Orientals that I've stored for up to six years. They do change, but it's just a slight mellowing.

I think the principal question to ask about cured rajangan is, "how finished does it taste?" If it needs some mellowing, then I would not do the 165°F heat treatment.

Bob

 

[Charly]

That's a good point, I should perhaps try to smoke some before deciding what to do with it !
If they are nice and sweet, I will try to put some in the oven at 165°F and save some without this heat treatment, this way I will be able to compare them later.

For how long should I heat the leaves at 165°F to destroy the enzyme ? 5 minutes ? 30 minutes ? 1 hour ? longer ?

 

[deluxestogie]

Oxidase denatured at 65°C to 66°C (149°F to 151°F)
Peroxidase denatured at 87°C to 88°C (188.6°F to 190.4°F)

I'm not aware of a duration required. Since we are discussing the thermal denaturing of a protein (the enzymes), I would assume it would denature much like the center of a steak. Once the center reaches a denaturing temperature, it is cooked. So that would suggest that keeping tobacco at 66°C momentarily would remove the primary oxidase. Taking it to 88°C momentarily should denature both oxidase enzymes (the primary oxidase as well as the peroxidase). The 24 hours at the maximum temperature that is used in flue-curing is to accomplish total drying of the stem as well.

I'm just guessing.

Bob

 

[ChinaVoodoo]

The general rule of thumb for denaturing the enzymes in grain responsible for starch conversion in beer is that at the target temperature, the enzymes "die" petty much immediately and that five minutes is sufficient. My guess is that this is the same for flue curing.