Bark, in the context of barbecue, is not just a random outer layer; it's the result of intricate chemical reactions, with the Maillard reaction and polymerization playing starring roles. The journey begins when we generously coat the meat with a spice rub, like the renowned Meathead’s Memphis Dust recipe. While rub ingredients may vary, they usually encompass the holy quartet of salt, pepper, sugar, and paprika. Beyond that, the possibilities are endless, with ingredients like garlic powder, onion powder, ginger, and ground bay leaf gracing the mix.
These spices embark on a unique adventure during the slow roasting process at around 225°F. The moisture from the meat, combined with water vapor from the smoke, dissolves the water-soluble compounds in the rub, like salt and sugar, forming a gritty slurry. Simultaneously, fats within the meat rise to the occasion, mingling with the rub and dissolving some of the fat-soluble spices.
Salt, however, possesses a unique ability to penetrate deep within the meat through electrochemical reactions with water. The other rub components, being too large to infiltrate the meat's interior, remain on the surface, effectively forming a glaze. Dispelling the myth that spices permeate the meat like migrating salmon, Blonder explains that meat is a complex structure of tiny compartments, with only salt able to breach these boundaries.
As the journey progresses, smoke particles adhere to this flavorful concoction, changing its color and taking it from a dark mahogany red to a mesmerizing licorice-black, shiny lacquer. Importantly, this transformation doesn't impart a burnt flavor, as evidenced by the coveted burnt ends, which are actually bite-sized cubes of meat encased in dark bark.
Simultaneously, water within the meat begins to evaporate, acting as a cooling mechanism and slowing down the cooking process. The spice rub does little to halt this evaporation, akin to sweat escaping from a marathon runner's body.
Contrary to popular belief, table sugar doesn't caramelize and darken until temperatures exceed 300°F, a feat unlikely at a cooking temperature of 225°F. Eventually, the rub dries, and the Maillard reaction takes center stage, albeit at a slower pace. Meat proteins bind and clump together beneath the spice crust, forming polymers and a pellicle—a thin, less than a millimeter thick, skin-like layer on the meat's surface.
In certain traditional Southern Barbecue joints, such as Archibald & Woodrow’s in Tuscaloosa, where only salt is used on ribs, the bark takes the form of pure pellicle—thin, ruddy golden, and occasionally peelable. Achieving the perfect pellicle is an art, as it can toughen if no moist rub is present or if cooker humidity is too low.
Blonder dubs this process "Diffusion Restricted Irreversible Polymerization" (DRIP) and dispels the notion that seasoning influences pellicle formation. His experiments reveal that salty and acidic rubs may expedite bark formation slightly, but by the time the meat is fully cooked, the differences are negligible. Fats play a role in moistening the bark but don't contribute to its creation. When spices are applied to a fat cap, you won't witness the pellicle magic beneath.
If you're a true bark aficionado, here are some tips to enhance your bark game:
Increase surface area by cutting your pork butt in half, removing any bones, and tying the parts into tubes with butcher string.
Avoid using a pan; expose the meat to maximum convection air flow.
Skip the Texas Crutch method, which involves wrapping meat in foil to expedite tenderness.
Consider gashing the meat in a crosshatch pattern, allowing the rub to penetrate deeper.
Remove the fat cap for optimal bark formation.
For the ultimate bark experience, explore the world of burnt ends from a brisket, a subject you can delve into further in the "Texas Brisket" article.