Tobacco Curing Methods
June 5, 2020 by Jeffery Sitts in Tobacco Talk
Courtesy of John Lambeth from the NCFB
While tobacco is a necessity for pipe and cigar smoking, it's easy to overlook its preparation and how the leaf begins its journey. Tobacco is an extremely sensitive crop and the soil, climate, and curing process it's exposed to all play crucial roles in its production. These factors determine where certain tobaccos can ideally be grown and harvested, making it impossible for a grower in one area to change to a type of seed that's primarily grown elsewhere and produce a leaf that's true to that specific seed.
Tobacco is harvested in one of two ways. The first harvesting method, called priming, involves removing the individual leaves from the growing plant as they mature and ripen in the field. The other method, called stalk-cut harvesting, is performed by cutting the entire mature plant's stalk at ground level with the leaves attached to the stalk.
Once harvested, tobacco must undergo what is called a curing process, which prepares the leaves for further processing as curing allows for the naturally occurring excess moisture within tobacco to be drawn out. When raw and freshly picked, tobacco is typically green in color and because of its excessive moisture, it won't easily ignite or be smokable. Tobacco curing is sometimes referred to as color curing because as the tobacco undergoes the process, the color of the leaf will invariably change because its chlorophyll content is being altered, gradually becoming more yellow to brown in color.
The primary tobacco curing methods consist of air curing, sun curing, fire curing, and flue curing. Each method has its own unique benefits and is used for different tobacco varietals, marking the first step in the manufacturing process of many of our cherished mixtures. I was also able to talk to Jeremy Reeves, head blender at Cornell & Diehl, about the methods and how they impact blends.
Air-Cured Tobacco
Air curing was among the first tobacco curing methods used; early settlers describe how Native Americans would dry tobacco leaves in the sun or in the shade of huts. Tobacco processing in the early colonies was primitive and evolved slowly over time. Initially, the leaves were simply picked and piled in heaps to dry but methods gradually advanced over time and it was discovered that tobacco cured better when hung.
Generally, air-cured tobacco is stalk-cut harvested and hung in well-ventilated barns for anywhere from three to twelve weeks and is complete when the leaf's central rib is free of moisture, resulting in leaves that are light tan to reddish-brown to deep brown in color. Maintaining low humidity is critical to the air curing process as the moisture may cause the leaf to mold or rot if not properly monitored. Sometimes fans are utilized to accelerate the drying process by forcing additional air into the tobacco. Once the curing is complete, the leaves can remain in the barns until they absorb just enough moisture from the air to make them pliable.
As a natural curing process for tobacco, air curing generally takes the longest of all the methods. Air curing yields tobacco with low sugar content that will usually impart a mellow flavor and higher levels of nicotine. "What you're left with is a very mellow, rich smoke and the tobacco is medium brown to dark brown in color," Jeremy explains. "It's more alkaline (less acidic) in its chemistry, making the nicotine more noticeable when smoked."
The most common types of air-cured tobacco are Burley and cigar leaf, though cigar leaf and dark Burley undergo an extra step called "bulking." After completing the air curing process the leaves are primed from the stalks and sorted based on their thickness and weight. Essentially, heavy bales of tobacco (also referred to as bulks) are piled together until enough pressure exists to begin a mild fermentation process. "Leaves that are particularly heavy and oily are the most desirable since they're able to withstand the higher temperatures they'll be subjected to during the fermentation process because thinner leaves will begin to degrade," Jeremy says.
The tobacco's weight, along with the moisture within the leaf (as well as moisture that is added by workers before assembling the bulk), helps create heat, which causes it to "sweat," or ferment, changing the chemical structure of the tobacco. Sometimes additional heat will be introduced to give the tobacco a dark brown color and ultimately help provide a sweeter flavor profile as the added heat helps caramelize the natural sugars within the tobacco.
As a natural curing process for tobacco, air curing generally takes the longest of all the methods.
"Bulking uses the leaf's natural biodegrading process but is controlled, giving the tobacco a deeper, fermented flavor," Reeves explains. That flavor is especially noticeable when comparing white and dark Burleys. "There's a little more spiciness and richness in dark Burley, sort of a clove/wine kind of flavor that you don't really find in white Burley."
Sun-Cured Tobacco
While some may consider sun-curing to be the same as air-curing, there is a slight difference between the two processes. Air-cured tobaccos are typically hung up in ventilated barns or shaded areas with the humidity closely monitored, while sun-cured tobaccos are spread out on racks and exposed to direct sunlight for a few days. This rapid drying method secures a bit of the natural sugar in the leaves, offering a slightly sweet taste when added to a blend.
Sun curing is predominantly used in the production of Oriental tobaccos grown in Asian and Mediterranean countries, regions where there is abundant sunlight and very little rain. Sun curing yields tobacco that is yellow to orange in color, has a high sugar content, and a lower level of nicotine. When sun-cured, the tobacco loses a significant amount of weight (sometimes up to 90%) due to the loss of moisture.
In terms of the flavor profile of sun-cured Oriental tobaccos, Jeremy offers a descriptive account of what he detects. "Sun-cured leaf tends to have a herbal, spicy character and Oriental tobaccos have a sweet and sour, somewhat nutty flavor," says Reeves, "and I often taste cashew, lemongrass, cardamom — those kinds of complex flavors."
Sun curing yields tobacco that is yellow to orange in color, has a high sugar content, and a lower level of nicotine.
And while sun-cured Oriental tobaccos aren't necessarily strong, they can be used to great effect as a versatile blending component. "They can add delicacy and complexity to a blend without actually making the blend stronger," says Jeremy. A typical English blend will often combine Oriental tobacco with Virginia and Latakia, though the proportions of each component may vary. However, the various flavors of each component can play off each other in interesting ways depending on the quantity used, the curing process they were exposed to, and any topping or flavoring added later in the manufacturing process.
Fire-Cured Tobacco
Utilizing fire in tobacco production evolved from the rapid development of curing techniques in the American colonies. Growers recognized that fire not only protected the leaves from dampness but could help preserve tobacco to be shipped abroad. It was also discovered that fire imparted a distinct finish and aroma to the tobacco, resulting in fire-curing in certain areas becoming a popular practice.
The fire curing process can almost be viewed as barbequing tobacco leaves, exposing the tobacco to a smoldering fire and imparting a distinctively smoky, woodsy flavor. Typically, fire-cured tobacco is hung in large barns similar to those used in air curing but are more tightly sealed to maximize the smoke exposure. The tobacco used for fire curing can either be stalk-cut harvested or the leaves may be primed off the stalk, depending on the farmer.
Fires of hardwoods are kept on a continuous or intermittent low smolder and the process lasts anywhere between three days and ten weeks, depending on the tobacco and the desired results. "A hardwood fire is built on the barn floor and then it's smothered with sawdust, which tamps out the flame and creates a consistent smoldering effect," says Jeremy. This type of gradual, uniform curing prevents the tobacco from losing its natural oils. Fire curing yields tobacco that is low in sugar, high in nicotine content, and adds a spicy kick to the flavor profile of the mixture it joins.
Much of the flavor from fire-cured tobacco has to do with the type of wood that is used during the process. "It's predominantly done in Tennessee and Kentucky and they're using oak and mesquite — hardwoods that have prominent flavors," Jeremy explains. The hardwoods are often mixed until the desired flavor profile or color is reached, allowing for experimentation within the fire curing process.
Due to the amplified strength and flavor of dark fire-cured tobacco, it's often used sparingly in mixtures. "Typically, dark-fired isn't used in large quantities in a blend because it can be a pronounced and overpowering flavor, so it's often used as a condimental tobacco," Reeves says. Some notable C&D blends that feature dark fired tobacco include Burley Flake #5, Redburn, and Dreams of Kadath with each one offering their own distinct flavor profile and highlighting dark-fired tobacco's versatility.
The fire curing process can almost be viewed as barbequing tobacco leaves, exposing the tobacco to a smoldering fire and imparting a distinctively smoky, woodsy flavor.
Latakia is a notable example of fire-cured tobacco. It's initially sun-cured before being cured further over controlled fires of aromatic woods and fragrant herbs. This two-step process helps give Latakia its distinctive black color and smoky, peppery flavor profile. While it's rather strong by itself in terms of intensity, Latakia is often used as a condimental component in English/Balkan-style blends.
Flue-Cured Tobacco
Flue curing refers to the type of barn used to cure tobacco and is a method that involves indirectly exposing the leaves to heat, created by transporting hot air, smoke, or steam through a pipe, or flue. That heat radiates throughout the enclosure, rapidly drying the tobacco and giving it a yellow color. At no point during flue curing is the tobacco directly exposed to any sort of fire or smoke like fire-cured tobacco.
The flue curing process was an accidental discovery that took place during the 19th century in Caswell County, North Carolina on the farm of Abisha Slade, a tobacco farmer and local politician. One of Slade's workers fell asleep while watching a barn of curing tobacco and the fires had begun to die down. In a desperate attempt to revive the flames, the worker seized charred logs from the nearby blacksmith shop and placed them on the dying fires (although some sources claim charcoal was used). The sudden application of drying heat successfully drove the moisture from the curing tobacco, resulting in leaves that were bright yellow in color.
In today's era, the older types of flue curing barns are hardly used anymore, although some are preserved along the east coast. Jeremy elaborated on the older flue curing method, saying "They would have fireplaces built into the outside of the barn and they would hang the tobacco inside the barn. The fireplaces had flues or chimneys that ran up the walls and across the ceiling, allowing the heat to build up inside the barn without any of the smoke coming into contact with the leaves."
Thanks to technological advancements and updated technology, propane is often used as a heat source and the modern barns are remarkably sophisticated. "Flue curing barns today are really hi-tech and can be computer programmed to control temperature and humidity to exactly the format that the farmer wants," Jeremy explains.
The flue curing process begins immediately after the tobacco is harvested from the field to minimize damage or potential spoilage and undergoes a three-step process where the tobacco experiences a gradual increase in temperature, with the barn's temperature raised to a progressively higher point until reaching anywhere between 100 and 175 degrees Fahrenheit. The condition of the leaves is carefully monitored throughout each step since the tobacco could be ruined if additional heat is applied at the wrong stage. The entire process usually takes four to six days, after which the barn doors are opened to allow the leaves to absorb moisture from the air.
Flue-cured tobacco will generally contain a higher sugar content compared to other curing methods, lower levels of nicotine, and impart a mild, slightly sweet flavor and aroma. Virginia tobaccos are the most commonly used varietal for flue curing. "When you hear the term Virginia, it's basically synonymous with flue curing, and a tobacco that's referred to as a 'Virginia-style' tobacco implies that it's flue-cured," Jeremy adds.
Thanks to technological advancements and updated technology, propane is often used as a heat source and the modern barns are remarkably sophisticated.
Different types of Virginia can be produced by manipulating the temperature and amount of time the leaves are exposed to the flue curing process. For example, says Jeremy, "bright Virginia is created by the leaf being flue-cured at a higher initial temperature and then dropping the temperature down very quickly." The amount of time and the temperature at which the tobacco is flue-cured will ultimately impact its color, strength, and flavor profile. "The yellower the leaf, the more natural sugar there is and the less nicotine there is by comparison," Reeves explains, "while in darker leaf, more of the sugar has been lost and as a result the nicotine will be more pronounced."
All of these curing methods are essential to the manufacturing processes of tobacco and what ultimately becomes our beloved blends. These processes have gradually evolved over the course of centuries, continually becoming more refined and improved upon through trial and error as well as an increased understanding of the leaf from a scientific approach. Each method yields different results and allows pipe smokers to expand their palates and find similar blends they may enjoy based on the manner in which the tobacco is cured.
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