396 MARINE PRODUCTS OF COMMERCE 



tain other substances pass out. Different types of membranes exhibit varying de- 

 grees of selectivity of the substances which are able to diffuse. This osmotic process 

 occurs when fish are placed in a strong salt solution. The selectivity of the skin 

 and cell membranes of the flesh is such that as water passes out some salt passes 

 in, while practically all the essential food materials are retained within the cells. 

 This principle of osmosis is therefore exemplified in all common salting processes, 

 and also in the first step (brining) of nearly all smoking processes. 



Use of Pressure. In some curing processes water is mechanically removed by 

 the exertion of pressure upon the fish. Piling and repiling cured fish in stacks, 

 with or without the use of added weights, is a common method of preparing dried 

 salted codfish. In the preparation of pressed sardines (salachini) the moisture is 

 extracted by means of machines or presses of various types. 



Application of Heat. Ordinarily heat is applied to stop, or at least retard, bac- 

 terial and enzymatic spoilage. However, in the cooking of fish, as in hot-smoking, a 

 part of the water is removed, which in itself is an aid to preservation. In prepar- 

 ing certain kinds of dried fish products a preliminary cooking, such as steaming or 

 boiling in water, is common practice and results in the removal of substantial 

 amounts of moisture before the actual drying process takes place. 



Absorption Through Use of Blotter- Like Pads, This interesting application 

 found some use years ago in curing dried codfish, but so far as known is not 

 being used commercially today. 



In preparing most dried fish moisture is removed by the application of one 

 method only: exposure to currents of air. Likewise in the salt curing of many 

 marine products the entire process is dependent on the principle of osmosis, 

 through the action of the salt applied. However, in many other cured items 

 two or more methods of removing moisture are employed; for example, various 

 smoking processes may make use of osmosis, pressure, and exposure to currents 

 of air and heat. 



Fish Smoking 



Introduction 



Although the origin of fish smoking is obscured by antiquity, aboriginal man 

 must have developed this method of preserving his catch from the sea shortly 

 after he discovered how to make fire. Undoubtedly one of the first foods that 

 our primitive ancestor learned to cook on an open wood fire was some form of 

 fish that he had succeeded in capturing by hand. Experience soon told him that 

 this barbecuing process not only made his food keep longer, but also added a 

 distinctive flavor. As time went on it became evident that the flavor varied with 

 the kind of wood burned, and those which gave the most pleasing flavor were 

 soon discovered. Other improvements followed gradually. Proper timing of the 

 barbecuing and correct temperatures, or to primitive man the correct position of 

 the fish with respect to the fire, were determined. As man became familiar with 

 the use of salt, he found that a preliminary salting or brining further improved 

 the flavor and keeping qualities of his fish products prepared over a wood fire. 



If records were available, from this crude beginning could be traced the evolu- 

 tion of present methods of hot-smoking or barbecuing, as it is sometimes called. 



