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< prev - next > Food processing KnO 100642_Smoked Foods (Printable PDF)
Smoked foods
Practical Action
more modern processing, pieces of meat are ‘tumbled’ with the salt mixture for 30-60 min in
a tumbling machine. The pieces are stored in a cool place for up to four days to allow the
liquid extracted by the salt to drain away. They are then hung in air to dry the surfaces before
Dry-salting has higher labour costs and less uniform salt penetration into the food than using
brine, but it is still widely practised in artisan tropical fish processing. In ‘Kench’ salting,
grains of salt are rubbed into the surface of split fish and the fish are stacked with a
sprinkling of salt between each layer. Care is needed in tropical climates to make sure that
the fish are fully covered by liquid pickle because any fish that are not covered are
susceptible to spoilage and insect attack. It is not possible to make good quality smoked fish
from spoiled fish: if fish spoil in the centre before the salt can penetrate, it produces ‘putty
fish’ that have a very soft texture that is unpalatable. Exposure to air also increases the risk of
rancidity and can give rise to discoloration and off-flavours. If fish are salted at a lower
temperature (e.g. 5°C), spoilage is dramatically reduced because salt can penetrate into the
fish before spoilage occurs. In many countries, large fish are split before salting to reduce the
thickness of flesh that the salt has to penetrate and so avoid this problem. The liquid pickle
that forms is allowed to drain away before smoking.
Fish may also be covered with saturated brine (360g salt per litre of water) as quickly as
possible after catching and kept covered until curing is complete. In tropical climates, this is
preferable to dry salting to avoid spoilage. A brining tank may be constructed from watertight
wooden or plastic barrels, stainless steel or food-grade plastic tanks, or concrete lined with
ceramic tiles and waterproof grouting. They should be fitted with lids that are weighted down
to hold the fish beneath the brine. The brine strength falls as water is removed from the fish
and salt should be added to maintain the strength of the pickle. Curing times vary from a few
hours to two weeks. Once curing is completed, the brine should be discarded and a new batch
In industrialised countries, curing most commonly uses brine that contains 25 kg salt, 3 kg
sodium nitrate and 50g sodium nitrite per 100 litres of water. Foods absorb salt more
uniformly from weaker brines, but the curing time is longer. Stronger brines can cause the salt
to crystallise on the surface of foods after smoking to create unsightly white patches. There
may be optional sugar, herbs and spices (including juniper berries, nutmeg, cloves,
peppercorns, rosemary or bay leaves) added to give particular flavours. The aim is to have a
salt concentration of more than 3% in the finished product. Fish or de-boned cuts of meat are
submerged in a tank of refrigerated brine (below 5oC), turning them occasionally. The brine
strength is checked daily using a brine hydrometer (Figure 1) that is calibrated to measure the
concentration of salt in brine. Depending on the result, curing salts are added to maintain the
brine strength. (Note: salinometers that are available to measure the salt in seawater are not
suitable because they only measure low concentrations of salt). If a salt hydrometer is not
available, brine of the correct strength will allow a fresh egg or a freshly peeled potato to float
in it (if it is too weak the egg or potato will sink). Other equipment to measure salt strength in
brines, such as a refractometer, are much more expensive.
Figure 1: A salt hydrometer to measure the strength of salt in brine. Photo: Pete Fellows
More rapid curing of meats can be achieved by injecting the meat with brine before curing in a
tank. This brine contains 30 kg salt per 100 litres of water and the same amount of sodium