% nicotine

[LeftyRighty]

Some of the seed catalogs list nicotine levels as a "percent of", for some strains of tobacco.
While it is nice to know which strains produce higher nicotine, if you're looking for a boost in your blends, exactly what is this a 'percent of what"???.
How is this determined, and how reliable is this number. Yeah, I know that this will probably vary greatly with weather, soil, location, etc., I would still like to know the basis of this number.
Thanks to anyone that can provide insight.

 

[Tutu]

One thread that might be interesting for you to read is this one. It's a discussion on nicotine levels in tobacco.
For me, as you already stated, this varies greatly in circumstances.
Although of course certain varieties have higher nicotine levels on average than others, this is far from an exact science.

 

[LeftyRighty]

thanks, that was helpful !

 

[deluxestogie]

How Nicotine is Measured

The nicotine content of N. tabacum varieties grown commercially generally ranges
from 0.3 to 3% of dry weight of the leaves, although 5% and even 7% have been reported.

LC-MS/MS results of nicotine concentrations in the leaf extracts ...

http://www.herbapolonica.pl/magazines-files/9607355-Tayoub et al.pdf

Alkaloids are extracted chemically from the dried leaf. It is then further separated and analyzed using liquid chromatography (LC) in combination with mass spectrometry (MS), in order to quantify specific components. This is measured in weight of nicotine per weight of liquid diluent, then converted to percent weight of dry leaf.

Nicotine and phosphorus content in leaf tissue decreased with decreasing soil temperature. A decrease in soil moisture decreased the growth but increased the nicotine content of tobacco. Phosphorus content was influenced little by soil moisture treatments. Low soil moisture treatments were more detrimental to growth of tobacco at the low soil temperature than at the higher ones. Phosphorus produced growth responses at the low soil temperature only. Nicotine content was not influenced by soil phosphorus treatments.

http://www.nrcresearchpress.com/doi/pdf/10.4141/cjps60-068

As you know, stalk level significantly influences the nicotine strength of a specific tobacco leaf. Which leaf level is measured for chemical analysis? Sometimes it is a consistent level for all varieties tested (e.g. the 10th leaf), sometimes it is an average of all the leaves from a number of plants, and more often, the research just doesn't clarify that crucial matter. I would venture to say that you already know more about nicotine levels in tobacco than most of the researchers.

Actual Impact of Reported Nicotine

Tobacco is generally in the ballpark of 5% nicotine by dry weight of leaf. But of that, only a tiny fraction is absorbed into the body when the tobacco is used--as low as 5% of the available nicotine. While the variety and growth conditions (including topping practices) certainly influence the final nicotine levels, curing and finishing methods may have just as much or more effect. Also, some studies equate "total alkaloids" with nicotine, which pretty much negates the value of the study.

Absorption is dramatically influenced by the route of exposure, as well as the pH of the tobacco smoke. The relatively acidic smoke of cigarette tobacco, if not drawn into the lungs, provides very little nicotine for absorption. By contrast, nicotine in the relatively basic smoke of cigar leaf is easily absorbed by the membranes of the mouth and nasopharynx. Any blend component that raises the pH (e.g. Perique) will increase nicotine absorption.

Bob's Conclusion

I believe that, as you have pointed out, the posted numbers may be somewhat useful for relative comparison of varieties, though I take them with a healthy dose of skepticism. I think each of us can easily figure out "stronger than" and "milder than", when it comes to our home grown tobacco. If you need to increase the nicotine effect, just alter the curing and blending methods and ratios.

Bob

 

[LeftyRighty]

good explanation, thanks, Bob,

How Nicotine is Measured

If you need to increase the nicotine effect, just alter the curing and blending methods and ratios.

Bob

So, which curing methods produce higher nicotine levels.?
And, why does the curing method influence the nicotine level.?

 

[deluxestogie]

So, which curing methods produce higher nicotine levels.?
And, why does the curing method influence the nicotine level.?

Ah! Slight of hand. Curing methods, and indeed even extensive aging, have minimal impact on the nicotine content. But curing methods (encompassing all post-color-cure processing) may affect the pH of the final tobacco. Methods also affect the sugar retention, which indirectly affects the pH of the resulting smoke. The pH does have a significant impact on the nicotine effect.

Increased sugar retention, as in flue-curing, results in a lower pH (more acidic) of the tobacco smoke, and so lowers the absorption of nicotine. Exhausting the residual carbohydrates (which is one of the effects of air-curing) raises the pH (less acidic) of the smoke.

I have the general impression (no scientific basis) that "sticky" tobacco increases nicotine absorption, and that kilning dissipates that "stickiness", and reduces nicotine absorption. This seems noticeable with 1 year old burley vs 1 year old kilned burley.

[Side note: We always talk about pH as a measure of acidity, but numerically, the pH scale is a measure of alkalinity. Higher number means more alkaline. It's an historical quirk of chemistry nomenclature, and a source of many a confusing sentence.]

Bob