330 PRESERVATION METHODS 



shrinkage. After about 24 houi^, the barrel is headed. In seven to ten days 

 the cure is completed. The herring may be held in chilled storage until 

 they are repacked. The fish are drained, packed in layers, back down 

 with a small amount of salt added (3 pounds per 100 pounds of fish). 

 The containers are then filled with 100° salinometer brine and held in 

 refrigerated storage unless they can be sold within a month or so. Be- 

 cause lake herring have very low oil content (one or two per cent) ran- 

 cidity is not a great problem, and the brine packed fish can be held in 

 chilled storage for up to a year's time. 



Properties of Salt. Beatty and Fougere- indicate that the most suitable 

 salt for the commercial salting of fish is a mixture of equal volume of 

 coarse salt (particles up to yi inch diameter) and fine evaporated salt. 

 The former possesses advantages in facilitating even spreading on the fish 

 and has less tendency to cake; the latter strikes more rapidly into the 

 fish. The salt should be free of halophilic bacteria and should contain little 

 impurities, particularly compounds of magnesium, iron, and copper. Very 

 small quantities of magnesium compounds may yield a whiter salt cod, 

 but presence of more than a few tenth per cent will retard penetration 

 into the fish. 



Processing Smoked Fish 



Equipment. In the United States a variety of equipment is used in the 

 smoking of fish. In older installations a common type of smokehouse 

 which is still quite generally used, shown in Figure 25.1, consists of a 

 vertical shaft of rectangular cross section extending upward through 

 several stories of the building. Doors at the lowest level lead to the fire 

 pit, at higher levels to areas where the fish are hung for smoking, and to 

 ventilators at the highest level. Such smokehouses have no provision for 

 controlling humidity and only approximate temperature control. 



In more recent installations both humidity and temperature can be 

 closely controlled. In many such operations the drying is carried out in a 

 chamber which is separate from the area where smoke is applied. The 

 fish are hung in a room into which air is admitted which has previously 

 been chilled and reheated to give the desired humidity and temperature. 

 The air velocity can also be adjusted. Smoke is then applied either in a 

 conventional older type smokehouse or sometimes by use of electrostatic 

 equipment^'. 



In other installations the controlled drying and smoking operation is 

 carried out in one smokehouse. Much research at Torry Research Station 

 in Scotland has resulted in design of the Torry controlled fish smoking 

 kiln^ which has been adapted to many commercial installations in Great 

 Britain and elsewhere. 



