240 Chapter 12
made of wood logs, and the burning logs are
covered with a layer of damp sawdust or
wood chips to keep the fl ame down and cause
smoldering of the woody material. Here the
control of the quantity and quality of the
smoke depends totally on the kind of sawdust,
the experience of the operator, and the
weather conditions. Increasing or decreasing
the volume of air entering into the fi replace
by widening or shutting the inlet openings
can adjust the smoldering temperature only
coarsely. The smoke produced in such condi-
tions may be high in PAHs. This principle is
applied also in industrially manufactured
generators, in which there are several boxes
connected to one smoke duct. Here the uni-
formity of smoke output can be better assured
by proper, simultaneous controlling of the air
inlets to the boxes.
In industrial smoking, generators are most
often used, in which the sawdust or wood
chips are automatically fed onto a plate or
grate heated to a controlled temperature of
about 350 ° C. The air needed for smoldering
is blown from below the plate. The tempera-
ture in the layer of sawdust depends on the
temperature of the heated grate and on the
volume of supplied air. When small mesh
sawdust is used, the fl ow of air may be hin-
dered and the temperature tends to be below
that of the plate. Such smoke is rich in
CO. Adding wood chips to the pile increases
the temperature and makes the smoke richer
in phenols. However, in the presence of too
large chips, the development of smoke may
be disturbed by the occurrence of fl ame.Friction - Type Generators
The principle of action of different construc-
tions of these generators depends also on
thermal degradation and partial oxidation of
woody material. However, the temperature
needed to initiate the process results from
friction of a log pressed at about 1 kg/cm^2
against a rotating drum or disk (Rasmussen
1956 ). Access of air is possible due to perfo-meat products smoked in traditional smoking
ovens than in meats processed in modern
smokehouses. The total amount of various
N - nitroso compounds in smoked fried bacon,
some of which are still unidentifi ed, has been
reported to be 430 – 6800 ng/g.
Heterocyclic aromatic amines, known to
be generated due to pyrolysis of amino acids
and proteins and in nonenzymatic browning,
may be found in very heavy smoked goods
in amounts lower than 1 ng/g.
The Equipment for Smoking
Introduction
The implements used for smoking meat and
fi sh have been gradually improved during
ages of development from very primitive
burrows or huts with a fi replace on the ground
to modern installations controlled electroni-
cally. However, in some parts of the world,
the most ancient procedures and equipment
may still be in use. In contemporary indus-
trial smoking, high attention is paid to the
temperature of smoke generation, proper
circulation of the smoke and drying air
in order to achieve the required degree
and uniformity of smoke deposition, water
evaporation, and heating, as well as to control
all process parameters affecting the quality
of the products. In accordance with the
requirements of hygiene and environmental
protection, the industrial installations also
include the necessary gear for effi cient
cleaning and for neutralization of the spent
smoke. The main components of smoking
equipment are the generators of smoke and
the smokehouses.
Smoke Generators
Smoldering - Type Generators
In primitive, usually small - scale or artisan
processing, the smoke is produced in a fi re-
place directly below the meat, which is hung
above it on spits or laid on a mesh. A fi re is