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How does humidity affect the rate of fermenting?

3800

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I've read every post in the fermenting section and searched for humidity-related posts and didn't see what I was looking for. I'm sure I'll have some people wonder why I care and remind me that they cured tobacco for hundreds of years without a lick of technology but I'm still curious. Can anyone tell me how humidity affects the rate of fermentation? I read quite a bit about fermentation needing water to complete its reaction. I've also read people expressing that you should keep it 65-70% RH and if it drops low and drys out don't sweat it (see what I did there?) because when humidity comes back up the reaction will carry on as normal. The way I understand that is that the fermentation resumes in relation to humidity levels. I would further assume that it increases in relation to humidity rather than just stopping/starting. I may be wrong in thinking this and if so that would answer my question but if fermentation does increase with humidity then it stands to reason that you would have the fastest fermentation at 100% RH right? Or maybe when the humidity gets high enough the fermentation rate slows back down. If optimal fermentation does happen at 100% what problems occur with humidity over 70% that keeps people saying "keep it at 70%RH and you'll be fine"? I'm looking for a theoretical scientific optimum for fermentation to happen along with practical real-world reasoning why optimum humidity doesn't equal optimum tobacco fermentation. I understand that optimum conditions, for one thing, can lead to very poor results when considering other influences. I'm trying to understand the science behind what happens in tobacco production.
 

deluxestogie

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My understanding of humidity vs. fermentation rate (in the absence of having performed controlled, randomized studies of it) is that the enzymatic reaction rate is entirely dependent on temperature, and simply requires sufficient moisture in order to proceed. Higher humidity would not impact reaction rate. Above 122°F, there is no risk of vegetative mold growth, regardless of the humidity.

One way to think of the fermentation situation is that the substrates in the leaf plus water molecules are the ingredients of the reaction. Enzymatic reaction rates increase exponentially with increasing temperature, up to the point at which the enzyme itself is denatured by the heat.

Bob
 

3800

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So if the heat is warmer (say128) than it will use more water (humidity) than it would when it was colder (say 122) right? But at neither temp will it require more moisture than ......70% humidity?
 

3800

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That's why everyone just says ~65-70%RH. This helps thank you. Have there been any studies that you know of that recorded this? I'm already deeper than I should be concerned with so I'll just go ahead and go deeper. Theoretically speaking at 70% humidity and 128F we have created the optimum conditions for the reaction to work. What is limiting the reaction speed after that? Oxygen? Sugars for bacteria? space? I'm just curious.
 

deluxestogie

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Bacteria are not involved in this process. Above about 130°F, the finished tobacco begins to take on a "baked" off-aroma, probably due to heat changes in some of the volatile aromatics that you really don't want to damage. Above 149°F, the primary enzyme itself is destroyed. (When you flue-cure, you intentionally destroy the enzymes, while raising the temp so rapidly--and in the absence of water--that it does not smell "baked". When you cook Cavendish, you get a different product entirely.)

For diving into the rabbit hole, just enter your desired search terms here:


Bob
 

ChinaVoodoo

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I caught a clipshot of a pilon manager's notebook in a cigar factory video, and the core temperatures never exceeded 118°. That's the warmest part of the pilon. I think humidity and water content in this factory environment does matter. I'm willing to guess, though, that most go by subjective experience rather than measurements.
 

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