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< prev - next > Food processing KnO 100642_Smoked Foods (Printable PDF)
Smoked foods
Practical Action
last design has high fuel efficiency and circulates smoke inside the smoker, which reduces
fuelwood consumption by more than 80% compared to traditional designs, and produces high
quality smoked fish. It has a large capacity, with up to 18 kg fish per tray and 15 trays per
smoker. Details of its construction are given by Brownell (1983) and Zinsou and Wentholt
Figure 3: Improved Chorkor smoker. Photo: from Jallow, 1994.
A note on safety of smoked foods
Smoked foods give rise to some health concerns because they contain dangerous chemicals
that are absorbed from the smoke. These include PAHs (polycyclic aromatic hydrocarbons),
nitrogen oxides and PCBs (polychlorinated biphenyls), and also nitrosamines that are formed
by reactions between gases in the smoke and components of the foods. These chemicals
increase the risk of gastrointestinal cancer where there is a high intake of heavily smoked
and/or salted foods. There are legal or recommended limits for these chemicals in smoked
foods in many countries. Using fires that have lower temperatures or reduced smoking times
can reduce the levels of these chemicals.
Cold-smoked fish, shellfish or meat products have a high risk of contamination by bacteria and
these foods require more stringent standards of hygiene and handling to avoid the risk of food
poisoning. Safety measures include using very fresh fish or meat that is chilled to 2oC before
smoking, and handling under strict hygienic conditions before and after smoking. After cold
smoking, foods should be chilled to 3°C in a coldroom and they should be packaged and kept
at chill temperatures during storage, distribution and retail display. These measures are
described in Good Manufacturing Practice (GMP) and Good Hygienic Practice (GHP)
guidelines (Anon, 1979; Anon, 2001) and are included in the food legislation in many
In some countries, hot-smoked meats and fish are not packaged and are sold loose in markets.
The main cause of spoilage is development of rancidity over several weeks due to exposure to
air and sunlight. In humid climates, moulds may cause spoilage of unpackaged smoked foods
and they should be packed in plastic bags to prevent moisture pickup.
In some countries, cold-smoked foods are packaged in vacuum packs or modified atmosphere
packs. These packs contain low levels of oxygen and thus slow the development of rancidity,
especially in fatty products such as cheese, meats or oily fish. However, the lack of air (or
anaerobic environment) inside these packs can allow the growth of food poisoning bacteria,
especially Clostridium botulinum: vacuum-packed smoked fish is one of the highest risk foods
to cause botulism. Small-scale processors who wish to use vacuum- or gas-packing for smoked
meats, fish or cheeses should be properly trained and have strict controls in place to avoid the
risk of botulism. Many countries have laws or recommended practices to prevent the growth of
Cl. botulinum. These include the use of temperature monitoring and time-temperature
indicators to ensure low storage temperatures; the use of sodium or potassium nitrite with salt
to cure foods; recommended smoking conditions (e.g. to give a core product temperature of
62.5°C for 30 min for fish that contains more than 2.5% salt); and storage at chill