There are two main processes for smoking fish. In cold smoking, which is used in most traditional British cures, the temperature of the smoke ought not to rise above 30 degrees Celsius or the fish will cook. In hot smoking, which until recently was more common on the continent, the intention is to cook the fish as well as smoke it.
The introduction of the mechanical kiln has made hot smoking of species like trout, mackerel and sprats more common in Britain but historically the two main hot smoked products were buckling, made from herring, and Arbroath smokies, made from small haddocks.
In Britain the popularity which has existed for a long time for cold smoked products, eaten steaming hot, in preference to the more continental hot smoked products, eaten cold, can be traced back to climate. Cold smoking using traditional methods is only possible in a cool climate like Britain’s and in cold weather hot food is appreciated most. Although these days the eating habits of different nations are not so clearly defined, the knowledge and skills that mark out the genuine product from imitations, continue to reside in the region which has had the longest association with the product in question, whether this be Camembert cheese, Parma ham or Grimsby Traditional Smoked Fish.
The knowledge built over years of traditional fish smoking in the port is essential in being able to produce consistent quality. This starts with buying the right type of fish; the condition of which alters radically as it passes through its annual breeding cycle. Grimsby is fortunate in that it has agents which bring in daily supplies of fresh whole cod and haddock from Iceland, Faroe and Norway.
These are the traditional fishing grounds from which the fish has been caught for generations and which provide the large haddock and firm cod needed for smoking. An experienced buyer can normally find suitable fish whatever the time of year.
Even so during the difficult spring and summer months it is essential to have expert filleters. And Grimsby has the largest pool of skilled fish filleters in the country. The fish then has to be smoked successfully and to do this fish smokers have to allow for the many variables of fish, season and weather. The smoking process begins with the fillets being immersed in salt water. The fillets are left in the brine for ten to fifteen minutes depending on the size of the fish and the season of the year.
Afterwards the fillets are allowed to drain on stainless steel rods called speats. At the end of the working day the speats of fillets are placed in smokehouse chimneys to be smoked overnight. These chimneys are one metre by two metres square and up to ten metres high. They have openings at top and bottom to allow a draught of cool fresh air to mingle with the smoke as it rises creating the special ‘cold smoking’ which the process requires. A door part of the way up each chimney allows the smoking process to be monitored and the fillets to be moved and removed as necessary. The walls of the chimneys have been allowed to gather a coating of tar over many years – essential in imparting the unique flavouring that can not be produced by any other method.
A shallow pit at the base of each chimney is filled with sawdust. The amount of already smouldering sawdust added to the fresh sawdust to start the burn alters considerably with the season and weather, with less needed in the summer. This variability caused mainly by changes in temperature and humidity can also be regulated by altering the amount of air in the laid sawdust. This is done by removing the air trapped in it: the more the sawdust is compressed the slower the burn.
The expertise required to smoke fish successfully in the traditional way can only be learnt over many years, with the knowledge often being handed from father to son. This is in contrast to the modern mechanical kiln, which is a sealed electric oven regulated simply by turning dials. This is a great advantage to people with little experience of fish smoking, but the product never has the same distinctive taste and aroma. Traditional fish smoking is an overnight process taking much longer than using a mechanical kiln. The first speats of fillets are removed from the chimneys early the next morning. The speats nearest the fires are taken out first with the higher ones being removed in batches over the next few hours. An experienced fish smoker can tell when the fillets are ready simply by touch.
The mixture of smoke and cold air, which has passed over the fillets, means that there is little heat involved in the process and it only takes a short time for them to cool. Once this has happened the fillets are packed into shallow cartons weighing between three and five kilos. Rapid chilling brings the temperature of the fillets to below 5 degrees Celsius. It is at this temperature that the finished product is transported, overnight, to its final destination.