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The secret to success is to use the *right* amount of the *right* compounds at the *right* time to achieve either preservation or flavoring. To this end, serious scientists have, over the years, made several studies of the constituents of smoke and the deposition of smoke flavor and coloring upon the meat. We will extract and summarize, and try to translate, the information from several of these studies as it relates to using smoke as a seasoning during cooking on a grill.
Wood smoke is generated from smoldering wood where there is insufficient oxygen for complete combustion to occur. That is why a smoky fire can be made to burn a bright, clean flame if you supply extra oxygen with a bellows, fan or hair drier. In the absence of oxygen, wood is destroyed by distillation, driving off liquids and gasses. These are primarily acetic acid, methanol, tarry complex aromatic compounds and furans (flammable liquid hydrocarbons).
With enough oxygen, these liquids are changed into gasses and volatile gasses are burned. The final products produced vary depending upon the amount of oxygen available, the temperature of the fire, the type and the moisture content of the wood. What this means is that every fire or smoke stream is unique.
Wood smoke is a colloidal aerosol which contains solid particles, liquid droplets and vapor. The vapor is invisible but contains the compounds which give the characteristic flavor that we expect of smoked food. This means that if you can see it, you don't want it. Prior studies showed that solid and liquid particles did not contribute significantly to the flavor of smoked food. Solid particles, which are visible, were shown to absorb compounds from the liquid and vapor to form solids which were deposited on the food as "tarry deposits".
About 40% of the moisture in the smoke is made up of acids, the major one being acetic which give the tart flavor to smoked food. About 25% of the smoke is carbonyls which is mostly ketones and aldehydes (bad news guys). Around 16% of wood smoke is made up of phenolics, various phenols, eugenols and vanillins. The carbonyls and phenols provide color and phenol is a preservative. Phenol is the source of the dominant odor, and the effectiveness, of the well known bathroom disinfectant, .............. Lysol.
Desirable, invisible, smoke flavor is deposited upon the surface of the meat then it is dissolved and diffused into the tissues. Acids accelerate the deposition, as does the difference between the food temperature and the temperature inside the grill. Therefore, early when the meat is just starting to cook, more flavor is deposited than later when the exterior of the meat approaches the temperature of the gasses in the grill.
Higher temperatures darken the surface of the food more than moderate temperatures. But the most important consideration in generating desirable smoke flavor is moisture content. A moist surface will absorb flavor while a dry surface will only attract tarry deposits. Thus, basting with a slightly acidic sauce will aid in the flavoring two ways. If the surface is kept moist and the temperature is moderate, barbecuing temperature -180-210 degrees, the absorption of beneficial flavors will continue and the color will be lighter than that cooked in higher temperatures with the deposition of tarry phenols and cresols.
At high temperatures, the maximum smoke deposition occurs rather quickly then stops. Lower temperatures extend the smoke deposition up to two hours, but most deposition occurs within the first hour. Meat and fish roasted and barbecued will get all the good smoke within the first couple of hours. Smoke after that will deteriorate the flavor.
When broiling, most of the flavor will be the result of the invisible vapors emanating from glowing embers. Throwing green/damp wood on immediately prior to putting the food on will generate more vapors, while the dense smoke is just passing by.
So the next time you see a grill belching dark smoke like an old coal fired railroad engine, have pity on the folk who have to eat the food. A faint wisp is all it takes.
© C. Clark Hale
8168 Hwy 98 E.
McComb, MS 39648
Smoky's 5th basic position for really great barbecue'n.
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