By Simon Krasemann
A History of Smoke Preservation
Foods have been preserved by smoke-curing since before the dawn of recorded
history. People in all cultures the world over have relied on the smoke-curing
of fish and meat products for long-term storage.
It is important to make a distinction between smoking for preservation, and
smoking for texture and flavour. Today the former is common in less developed
countries where transportation and climate extremes may be a factor. The later
is popular in developed countries where refrigeration and an integrated
logistical infrastructure for the efficient transportation of perishables is in
In its simplest form smoking meat and fish is similar throughout the world
depending on the end product desired. Preservation can be accomplished by first
cutting the flesh into thin strips and then drying them slowly over a fire — or
in the sun in northern climes).
Packed as dried smoked products, these can travel great distances and remain
edible for long periods of time. In all these processes, drying is of paramount
importance for preservation, because it is moisture in the flesh that permits
bacterial activity and spoilage. Salt accelerates the removal of water and hence
its widespread use as a traditional perservative. Further, the application of
extracts from the smoke (phenols, etc.) retards the development of spoilage
IN EUROPE AND BRITAIN DURING
THE MIDDLE AGES various heavily smoked and salted foods were relied upon to
carry people over the lean times of late winter and into spring. Fresh fish
could not be transported any distance from the port of landing unless they were
preserved. Two of these products were Red Herring and Salt Cod. Red Herring was
made with heavily salted herring that was smoked for up to three weeks in a kiln
similar to those in use today to make "bloaters" on Grand Manan, New Brunswick
These herring, used initially in the home markets, were widely
exported (and continue to be so today) to the West Indies in the infamous
"Triangle Trade" between Britain, its Northern Colonies and the West Indian
plantations. While not smoked, Salt Cod supported the expansion of trade routes
throughout the world, and is a prime example of how a simple product can be of
supreme importance to merchants — and the extension of government policy.
THE RAPID GROWTH OF LOGISTICAL INFRASTRUCTURE
(railways and steamships) beginning in the 1840's, enabled the transportation of
perishables. For the first time in human history it was possble to move large
quantities fresh fish from one place to another. This marks the beginning of
sea-fishing industrialization. As a result of the widespread availability of
fresh fish, the popularity of heavily salted, heavily smoked products — a
mainstay for hundreds of years — began to decline. In the same period (mid
1800's), the smoked fish products we now regard as traditional came into being.
These are mildly smoked and dried and contain minmum salt as condiment.
kipper for example was invented by John Woodger at Seahouses in Northumberland
about 1843 after considerable experiment. Within a few years it had become very
popular and remains so today.
Where the primary reason for smoking fish had been formerly to preserve it,
it was now mainly to impart a pleasant mild smoky flavour. Rapid transportation
for foodstuffs meant a long shelf-life was no longer so essential.
THE MARKET FOR SMOKED FISH UNDERWENT A MAJOR CHANGE
in the mid to late nineteenth century. And yet the actual technology of smoking
fish remained much the same as it had been for centuries.
It was not until
1939 that the Torry Research Station in Aberdeen, Scotland developed the Torry
Kiln that a reliable tool was generally made available to the industry. This
mechanical kiln can be relied upon to produce a high-quality, uniform product
time after time. The use of a forced-draft greatly enhances drying and smoke
application and with the use of a heat source remote to the smoke generator a
much reduced smoking time is achieved. This accomplishes two things; first, the
fish is exposed to moderate temperatures (prime for bacterial growth) for a
shorter period and secondly, the kiln-operator can process more fish in a given
time and produce it at a consistently higher quality.
Many companies now produce kilns based on this proven technology of laminar
air-flow through the product. The increasing use of micro-processors has added
another quality factor that insures consistency and adaptability in processing
any smoked seafood product for varying demands in any marketplace (differing
salt levels, moisture content requirements, etc.).
On a personal level we
have been asked if the application of all this technology removes us from the
actual business of producing a really top-notch food. The answer is both yes and
no. Yes, we don't have to baby-sit every load of fish now-it is controlled much
more closely than any human could actually do it ourselves (people need breaks,
holidays, etc.). The answer is no, it doesn't remove us from the process because
the computer faultlessly carries out what we have programmed into it earlier.
The result is as uniform and consistent as the changing nature of fish will
The Physical Properties of Smoking Fish
TAKES FIRST CLASS FISH to make a first-class product. Like the old saying
"garbage in, garbage out," a good product can't be made from stale fish. Some
folks believe that smoking can cover up moldy or stale fish off-flavours. This
is false. Any unpleasant odours or flavors will be readily apparent in short
Haddock Golden Cutlet
Given that the
fish are of good quality and free from disease it is important to look at the
natural condition of the fish. In the North-East, for instance, spring herring
and mackerel are low in fat and make a poor quality product. Haddock that have
recently spawned cannot be expected to turn-out well. Atlantic salmon with a fat
content much in excess of 14% becomes too oily and can oxidize rapidly after
Fish for smoking must be fresh and certainly post-rigour. Some
keep longer than others. Trout for instance, will keep longer than mackerel
which keep longer than silver-hake (given similar washing, handling, and icing)
and so on. In short, get to know the fish your dealing with before you jump in
and produce something even your dog wouldn't touch.
After preparation which may include, filleting, or nobbing, splitting or
chunking, the fish is either brined or packed in fine dry salt (brining being
more common nowadays). Once salted, the fish are placed in the kiln for a period
of time and allowed to drip. This allows excess liquid to drain off and in
certain products, allows the formation of an attractive gloss. The gloss is
actually the drying of a water soluble protein and such a pellicle is the mark
of a high-quality smoked whitefish like cod or haddock. Fatty fish will develop
a gloss also, but this can be generated by the oil that comes to the surface
during smoking. Fish packed in dry salt will not form a pellicle of the same
Most fish is cold-smoked, meaning no point will the temperature be
allowed to exceed 34°C. Cold smoked products include: Lox, Haddock, cod and
Kippers. Hot smoking on the other hand, is the slow raising of the kiln
temperature to in excess of 60°C to cook the product. Seabright hot smokes:
Mackerel, Shrimp, Scallops and Salmon. These products are generally flaky in
texture and are ready-to-eat.
IT IS BEST TO CONSIDER THE TWO
PROCESSES of smoking and drying separately, as controlling one does not
necessarily mean controlling the other.
Smoke should be produced from a smoldering, saw-dust fire. Wood smoke is
composed of millions of microscopic particles which rise like a fog, and by
vapours. The fog is mostly water, carbon and trace solids. The vapour contains
what we're after, namely volatile oils which are released from the wood and
furnish the characteristic flavours and preservative qualities.
The choice of wood for smoking varies a great deal with geography. Most
reputable smokers spurn the use of softwoods in favour of hardwoods (Oak in the
United Kingdom; Alder on the West coast of North America). Experienced smokers
also know that given a quality hardwood source, variations in species will
result in only small flavour differences. So there is ample latitude to refine
one's recipe! Some advocate the use of more resinous woods with oilier fish like
mackerel to counter its strong taste. Softwood dust is sometimes added when
smoking white fish to bring up colour more rapidly. A general rule of thumb
would have it that if a piece of smoked fish tastes "pitchy" it has more to do
with the temperature of the fire then the type of wood you use.
At Seabright the exact formula for
our wood smoke is a closely guarded. Yet everyone here knows we use native Nova
Scotian hardwoods and over the years we've found ground juniper can be used with
great positive effect.
A hot fire (blazing flames, little smoke and more
complete combustion) actually tends to burn off the volatile oils and reduces
them to more stable tar type resins. Pretty yuckey all round. So keep the fire
down, cool and watch out for flare-ups.
WHETHER DRYING OCCURS AND THE SPEED OF
DRYING is influenced by a number of factors: the speed of the air-flow; the
moisture content of the fish; the temperature and moisture content in the smoke;
and most important; the relative humidity (RH) in the surrounding air.
Relative humidity is generally expressed as a percentage in relation to the
temperature. Therefore if the RH is 100% at 20°C and you cool the air just
slightly — presto it rains. Let's assume however, that the temperature is about
16°C at 75% RH. This air will not dry fish very quickly at all but, if we raise
the air temperature to 30°C, the RH would fall to about 45%. An RH of about 65%
at a temperature of 30°C, is about perfect for most climates (if possible). If
the RH falls too far below this the fish will dry too rapidly and
"case-hardening" can result. A high RH in excess of 75% will prevent effective
drying from taking place.
Temperature and smoke should be controlled separately. We have seen that we
need a cool fire but we need an internal kiln temperature of at least 30 to
35°C. How to achieve this? Generate the smoke "remotely" from the actual kiln
and provide heat from either electrical elements or natural gas burners in the
kiln. Sure people did, and do, generate both smoke and heat together but not if
you are seeking a reasonable consistency. We don't want salmon that's to die for
this week — and salmon that will kill you the next. Consistency will be hard
enough to come by in any case. Don't worry about a boring product. If its good
it won't be boring!
Kilns or "What can I smoke it in?"
MENTIONED, KILNS HAVE come a long way in a comparatively short period of time
and there can be some confusion as to which would work best for you. First,
consider what kind of fish you're smoking and what kind of product you want out.
Cold-Smoking is the most difficult to achieve on a consistent basis so, if
you're just starting out, I recommend Hot-Smoking. This gives a fully cooked
product and can handle the greatest range of fish. Smoked Mackerel, Eel, Salmon,
Sturgeon, even small Haddock and Cod can be delicious if hot smoked.
A simple Hot-Smoker can be an old refrigerator — or even a barrel can work
reasonably well. Just make sure what you are using is clean. Clean sawdust from
a cabinet-maker (NOT from a power-saw-it's got chain-oil in it!) or a local
saw-mill. Get the finest "grind" you can. If the dust is too coarse the point of
flame temperature may get too high and you'll wind up with a raging fire.
Remember, a slow, smoldering fire is what you need. An electric hot-plate (to
provide the heat required), an indoor/outdoor thermometer (this allows you to
monitor the smoke temperature to ensure it comes up slowly and regularly), a few
racks (stainless steel, or chrome-plated steel/brass will work fine but NO
exposed brass, copper or other material that corrodes quickly or you could start
ingesting some very undesirable elements).
Years ago I used an old bucket with some heavy
steel mesh over the top (to prevent "smuts" or ash from blowing onto your fish)
and lit my sawdust in that. At the time I also scavenged the fan from an old
computer and stuck that at the top to blow the smoke about a little. We would
recommend sitting your kiln away from anything else that can burn (it wouldn't
be the first time someone either burnt their house down or caught the woods on
fire at the cottage doing this and it can really be a drag on the whole
Process the fish. Keep plenty of notes, including times, weather,
temperature (inside the kiln and out), salt/brining times and strengths (brine
strength can be measured using a hygrometer available from a hardware store (car
battery tester) or from a brew shop (measuring alcohol levels). They all do the
same thing-measure the density of water so when you add water the density
increases and it floats higher in the solution.
Because liquids become more or less dense with temperature the
above table is for use with water at about 60°F. After your first experiment.
Cool the fish rapidly after it reaches ambient temperature. Sample the product
yourself before you feed it to any anyone else. Keep everything VERY clean and
disinfected. Most of your products will keep very well in a fridge (well
wrapped) for about 10 days.