Smoking is the process of flavoring,
cooking, or preserving food by exposing it to the smoke from
burning or smoldering plant materials, most often wood. Meats
and fish are the most common smoked foods, though cheeses,
vegetables, and ingredients used to make beverages such as
whisky, Rauchbier and lapsang souchong tea are also smoked.
Europe, alder is the traditional smoking wood, but oak is more
often used now, and beech to a lesser extent. In North
America, hickory, mesquite, oak, pecan, alder, maple, and
fruit-tree woods, such as apple, cherry and plum, are commonly
used for smoking. Other fuels besides wood can also be
employed, sometimes with the addition of flavoring
Chinese tea-smoking uses a mixture of uncooked rice, sugar,
and tea, heated at the base of a wok. Some North American ham
and bacon makers smoke their products over burning corncobs.
Peat is burned to dry and smoke the barley malt used to make
whisky and some beers.
In New Zealand, sawdust from the native manuka (tea tree)
is commonly used for hot smoking fish. In Iceland, dried sheep
dung is used to cold smoke fish, lamb, mutton and whale,
resulting in a unique and rather strongly smoked flavor.
Historically, farms in the western world included a small
building termed the smokehouse, where meats could be smoked
and stored. This was generally well-separated from other
buildings both because of the fire danger and because of the
Cold smoking can be used as a
flavor enhancer for items such as chicken breasts, beef, pork
chops, salmon, scallops, and steak. The item can be cold
smoked for just long enough to give some flavor. Some cold
smoked foods are baked, grilled, roasted, or sautéed before
eating. Smokehouse temperatures for cold smoking are below 100
°F (38 °C). In this temperature range, foods take on a smoked
flavor, but remain relatively moist. Cold smoking does not
Hot smoking exposes the foods to smoke and heat in a
controlled environment. Although foods that have been hot
smoked are often reheated or cooked, they are typically safe
to eat without further cooking. Hams and ham hocks are fully
cooked once they are properly smoked. Hot smoking occurs
within the range of 165 °F (74 °C) to 185 °F (85 °C). Within
this temperature range, foods are fully cooked, moist, and
flavorful. If the smoker is allowed to get hotter than 185 °F
(85 °C), the foods will shrink excessively, buckle, or even
split. Smoking at high temperatures also reduces yield, as
both moisture and fat are "cooked" away.
Smoke roasting or smoke baking refers to any process that
has the attributes of smoking combined with either roasting or
baking. This smoking method is sometimes referred to as
"barbecuing", "pit baking", or "pit roasting". It may be done
in a smoke roaster, closed wood-fired masonry oven or barbecue
pit, any smoker that can reach above 250 °F (121 °C), or in a
conventional oven by placing a pan filled with hardwood chips
on the floor of the oven so the chips smolder and produce a
smokebath. However, this should only be done in a
well-ventilated area to prevent carbon monoxide poisoning.
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
"smokey" taste, while syringol is the primary contributor to
smokey 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
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
The optimal conditions for smoke flavor are low, smoldering
temperatures between 570 and 750 °F (299 and 399 °C). 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
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 smoker
There are a few basic
types of smoker designs, each with their own advantages and
The main characteristics
of the offset smoker are that the cooking chamber is usually
cylindrical in shape, with a shorter, smaller diameter
cylinder attached to the bottom of one end for a firebox.
To cook the meat, a small fire is lit in the firebox, where
airflow is tightly controlled. The heat and smoke from the
fire is drawn through a connecting pipe or opening into the
cooking chamber. The heat and smoke cook and flavor the meat
before escaping through an exhaust vent at the opposite end of
the cooking chamber.
Most manufacturers' models are based on this simple but
effective design, and this is what most people picture when
they think of a "BBQ smoker." Even large capacity commercial
units use this same basic design of a separate, smaller fire
box and a larger cooking chamber.
The Upright Drum Smoker (also
referred to as an Ugly Drum Smoker or UDS) is exactly what its
name suggests; an upright steel drum that has been modified
for the purpose of pseudo-indirect hot smoking. There are many
ways to accomplish this, but the basics include the use of a
complete steel drum, a basket to hold charcoal near the
bottom, and cooking rack (or racks) near the top; all covered
by a vented lid of some sort. They have been built using many
different sizes of steel drums (30 gallon, 55 gallon, and 85
gallon for example), but the most popular size is the common
55 gallon drum.
This design is similar to smoking with indirect heat due to
the distance from the coals and the racks (typically 24"). The
temperatures used for smoking are controlled by limiting the
amount of air intake at the bottom of the drum, and allowing a
similar amount of exhaust out of vents in the lid.
UDSs are very efficient with fuel consumption and flexible
in their abilities to produce proper smoking conditions, with
or without the use of a water pan or drip pan. Most UDS
builders/users would say a water pan defeats the true pit BBQ
nature of the UDS, as the drippings from the smoked meat
should land on the coals, burning up, and imparting a unique
flavor one cannot get with a water pan.
Vertical water smoker
A vertical water
smoker (also referred to as a bullet smoker because of its
shape) is a variation of the upright drum smoker. It uses
charcoal or wood to generate smoke and heat, and contains a
water bowl between the fire and the cooking grates.
The water bowl serves to hold the temperature down and also
to add humidity to the smoke chamber. In addition, the bowl
catches any drippings from the meat that may cause a flare up.
Vertical water smokers are extremely temperature stable and
require very little adjustment once the desired temperature
has been reached.
Because of their relatively low cost and stable
temperature, they are sometimes used in barbecue competitions
where propane and electric smokers are not allowed.
A propane smoker is
designed to allow the smoking of meat in a somewhat more
controlled environment. The primary differences are the
sources of heat and of the smoke. In a propane smoker, the
heat is generated by a gas burner directly under a steel or
iron box containing the wood or charcoal that provides the
The steel box has few vent holes, on the top of the box
only. By starving the heated wood of oxygen, it smokes instead
of burning. Any combination of woods and charcoal may used.
This method uses less wood.
Smoke box method
This more traditional
method uses a two box system: The fire box and the food box.
The fire box is typically adjacent or under the cooking box,
and can be controlled to a finer degree. The heat and smoke
from the fire box exhausts into the food box, where it is used
to cook and smoke the meat. These may be as simple as an
electric heating element with a pan of wood chips placed on
it, although more advanced models have finer temperature
Commercial smoke house
smokehouses, mostly made from stainless steel, have
independent systems for smoke generation and cooking. Smoke
generators use friction, an electric coil or a small flame to
ignite sawdust on demand.
Heat from steam coils or gas flames is balanced with live
steam or water sprays to control the temperature and humidity.
Elaborate air handling systems reduce hot or cold spots, to
reduce variation in the finished product. Racks on wheels or
rails are used to hold the product and facilitate movement.
Smoke is an antimicrobial
and antioxidant, but smoke alone is insufficient for
preserving food in practice, unless combined with another
preservation method. The main problem is the smoke compounds
adhere only to the outer surfaces of the food; smoke does not
actually penetrate far into meat or fish. In modern times,
almost all smoking is carried out for its flavor. Artificial
smoke flavoring can be purchased as a liquid to mimic the
flavor of smoking, but not its preservative qualities (see
also liquid smoke).
In the past, smoking was a useful preservation tool, in
combination with other techniques, most commonly salt-curing
or drying. In some cases, particularly in climates without
much hot sunshine, smoking was simply an unavoidable side
effect of drying over a fire. For some long-smoked foods, the
smoking time also served to dry the food.
Drying, curing, or other techniques can render the interior
of foods inhospitable to bacterial life, while the smoking
gives the vulnerable exterior surfaces an extra layer of
protection. For oily fish smoking is especially useful, as its
antioxidant properties delay surface fat rancidification.
(Interior fat is not as exposed to oxygen, which is what
Some heavily-salted, long-smoked fish can keep without
refrigeration for weeks or months. Such heavily-preserved
foods usually require a treatment such as boiling in fresh
water to make them palatable before eating.