Wood smoke -smoked country-style ribs
Hardwoods are made up mostly of three materials:
cellulose,
hemicellulose, and
lignin. Cellulose and hemicellulose are the basic structural material of the wood
cells; lignin acts as a kind of cell-bonding glue. Some
softwoods, especially
pines and
firs, hold significant quantities of
resin, which produces a harsh-tasting soot when burned; these woods are not often used for smoking. Cellulose and hemicellulose are aggregate
sugar molecules; when burnt, they effectively
caramelize, producing
carbonyls, which provide most of the color components and sweet, flowery, and fruity aromas. Lignin, a highly complex arrangement of interlocked
phenolic molecules, also produces a number of distinctive aromatic elements when burnt, including smoky, spicy, and pungent compounds such as
guaiacol,
phenol, and
syringol, and sweeter scents such as the
vanilla-scented
vanillin and
clove-like
isoeugenol. Guaiacol is the phenolic compound most responsible for the "smoky" taste, while syringol is the primary contributor to smoky aroma. Wood also contains small quantities of
proteins, which contribute roasted flavors. Many of the odor compounds in wood smoke, especially the phenolic compounds, are unstable, dissipating after a few weeks or months. A number of wood smoke compounds act as preservatives. Phenol and other phenolic compounds in wood smoke are both
antioxidants, which slow
rancidification of animal fats, and
antimicrobials, which slow bacterial growth. Other
antimicrobials in wood smoke include
formaldehyde,
acetic acid, and other organic acids, which give wood smoke a low
pH—about 2.5. Some of these compounds are toxic to people as well, and may have health effects in the quantities found in cooking applications. Since different species of trees have different ratios of components, various types of wood do impart a different flavor to food. Another important factor is the temperature at which the wood burns. High-temperature fires see the flavor molecules broken down further into unpleasant or flavorless compounds. The optimal conditions for smoke flavor are low, smoldering temperatures between . This is the temperature of the burning wood itself, not of the smoking environment, which uses much lower temperatures. Woods that are high in lignin content tend to burn hot; to keep them smoldering requires restricted
oxygen supplies or a high moisture content. When smoking using wood chips or chunks, the combustion temperature is often raised by soaking the pieces in water before placing them on a fire. == Types of smokers ==