THE PRESERVATION OF FISH BY SMOKING AND DRYING 405 



located a suitable distance from the main house and tlie smoking chamber is of 

 fireproof construction. 



7. Waste of the smoked product, usually caused by flying fish and dropping 

 on the Hoor, is reduced. 



8. The controlled smokehouse is adaptable; that is, it may be used for any 

 species or form of fish. 



Many controlled smokehouses are now in use both here and abroad. The 

 Torrey Research Station in Scotland has developed a very large, well-designed 

 structure that has been widely approved and is being adopted by the large 

 Scottish smoked fish industry, as well as by the industry in other parts of the world. 

 The Norwegians have also perfected kilns embodying many of the features neces- 

 sary to controlled smoking, especially for smoking prior to canning. Both the 

 Atlantic and the Pacific Stations of the Fisheries Research Board of Canada have 

 built controlled smoke ovens for fish curing. In the United States several types of 

 controlled meat-smoking apparatus have been placed on the market, some of which 

 have been used more or less successfully for curing fish. 



During the war years there arose in the Pacific Northwest a considerable trade 

 in smoked canned fish products. Some of these items were cold-smoked and 

 others hot-smoked before canning. Some were processed in chunks or small pieces 

 and others in large pieces or sides. In an effort to devise a smoke oven flexible 

 enough to meet these conditions and at the same time be relatively simple and 

 inexpensive to build the senior author of this chapter developed an oven that has 

 been widely accepted in the Pacific Northwest. Details of a pilot plant are de- 

 scribed by Anderson and Pedersen (1947). Since publication of this report several 

 additional plants have been built in other parts of the United States. 



In all the above there is no radical change in the time-honored processes of 

 smoking, but merely attempts to control the variable factors that often made the 

 old-fashioned methods unreliable. However, in recent years some new procedures, 

 such as vacuum- and precipitation-smoking, have been introduced; these are 

 based on entirely different principles. Of interest in this connection is the electro- 

 static precipitation process for smoked sardines. 



Large scale canning of smoked Maine sardines has necessitated a quick method 

 of smoking the product, and developmental work by the University of Maine and 

 the U. S. Fish and Wildlife Service has led to the use of an electrostatic device 

 (Hamm and Rust, 1947). In this process the filled cans are conveyed through the 

 smoking chamber; as they pass through, they form the negative side of an electric 

 field of 14,000 to 23,000 volts. In about 12 seconds the fish are sufficiently 

 smoked. The cans then continue on the conveyor to be filled with oil and sealed. 

 The greatest difficulty encountered in this process is in the production of smoke 

 of the desired quality. If there is any flame present in the smoke-producing fire, 

 there is a tendency for soot to deposit on the fish in the precipitation chamber. 



Smoke-Curing Processes 



It must be emphasized that only fish or shellfish of good quality should be 

 used for smoke-curing. Smoking will not mask or conceal the poor flavor and 

 quality of inferior raw material. The strictest sanitation should be maintained at 

 all points in the procedure. Most smoked and kippered fish are perishable and 

 should be handled accordingly. Careless handling will result in a product of poor 



