I’ve done it. You’ve probably done it as well. At one point or another, most cigar and wine enthusiasts have gotten a little carried away with their flavor descriptors. The aroma of a premium cigar or the bouquet of good wine cries out for comparison to the other fragrances we encounter in our daily lives, but the subjective nature of this comparison often mystifies those who are less sensitive to the subtleties involved.

So we take the occasional lump for detecting notes of caramelized sugar or violets or vanilla beans in our stogies. Everyone will acknowledge that taste is subjective, and the fact that you smell cedar where I detect mint does not mean that either of us has faulty olfactory organs — but few cigar smokers recognize the physical reality, the purely chemical nature of the combustion taking place beneath their noses.  To some extent this process has been studied, and this series of occasional articles will attempt to shed some light on it.

But first, a caveat. I am not a scientist, and I am certainly not a chemist. All I’ve done here is layman’s level research, and I can’t pretend to understand the chemistry in detail. If I mislead or mistate something, I hope someone with expertise will correct me, and accept my thanks for doing so.

Introduction

Much of the aroma and flavor of cigar tobacco arises from careful curing and fermentation. As the leaves dry and undergo a natural but controlled process of degradation, chemical compounds break down and create other compounds. Many of these compounds are responsible for the flavor and aroma of cigar tobacco.

Leaves from different stalk levels vary in their chemical properties — the highest leaves on the plant  (ligero) have higher nicotine levels, tannins and resins. As most of us have experienced at one time or another, a ligero-heavy cigar is frequently powerful and highly aromatic, but doesn’t burn very well . Middle and lower leaves (seco and volado) tend to have lower levels of nicotine, less resins, higher soluble ash, and better burning properties.  The importance of careful blending of leaves from different parts of the plant is easy to see here.

In general, the strength of a cigar tobacco leaf is associated with nitrogen compounds. Aromaticity is thought to come from tannins and resins. Sugars and starches are are associated with mildness.

Curing

As soon as a leaf is separated from the stalk during the harvesting process it begins the process of curing.  In cigar production the newly primed leaves are removed to a curing barn where the tobacco is hung for curing in the open air. As the leaves turn from green to brown, the following physical and chemical transformations occur:

• Dehydration
• The percentage of starch in the leaf is greatly reduced while sugars increase
• Tannins are reduced
• Proteins hydrolize to amino acids
• Alkaloids (including nicotine) decrease
• Carotenoids begin to degrade into important aroma constituents

Fermentation

Cigar tobacco that has been properly cured is not quite ready to be bunched and rolled — it must be fermented first. Stacks of tobacco called pilones are created and allowed to heat up. The combination of heat and water (from the leaves themselves and also applied by workers) causes further chemical decomposition. The main processes that occur during this stage are the following:

• A further reduction in tobacco alkaloids (especially nicotine)
• Production of ammonia
• An increase in amide and α-amino nitrogen levels
• pH increase due to elimination of organic acids through oxidation and decarboxylation

Oxidation is the primary activity occuring in the pilones during fermentation, and this is chiefly responsible for the flavor and aroma of cigar tobacco.  During this process the cured tobacco releases carbon dioxide and significant quantities of ammonia.

Basic Chemical Constituents

For social and health reasons, tobacco is  the most exhaustively studied natural product on earth. Around 5000 different chemical compounds have been identified, and studies continue. But the primary constiuents responsible for taste, flavor, and burning properties are the following:

• Carbohydrates, which account for 40 to 50% of tobacco weight. These include starches and sugars, sugar esters, cellulose, and pectin.
• Alkaloids, including nicotine
• Plastid Pigments: chlorophylls and carotenoid pigments
• Isoprenoids, which are important aroma and flavor contributors. This class includes degraded carotenoids, acyclic isoprenoids, carbocyclic diterpenoids, cembranoids, and labdanoids
• Carboxylic Acids. Cigar tobacco is particularly high in citric and malic acids.
• Phenolics, including polyphenols and lignin, which are also important aroma compounds
• Inorganics like calcium, magnesium, and potassium. These affect burning and ash-holding characteristics.

In future articles I will be looking at the compounds most responsible for taste and aroma, the isoprenoids and phenolics. And if I can pin down the compound responsible for that elusive vanilla note, I will be sure to let you know.

References

Tso, T.C. (1999) “Seed to Smoke.” Tobacco: Production, Chemistry and Technology

Leffingwell, J.C. (1999) “Basic Chemical Constituents of tobacco Leaf and Differences among Tobacco Types.” Tobacco: Production, Chemistry and Technology