Page:Principles preservation fish by salt.djvu/27

Rh to insert a needle in the gill arch and with pressure completely irrigate the whole system of arteries and veins of a fish, removing absolutely all the blood at one stroke without cutting the fish.

The preservation of fish by means of salt is an excellent method, even in the crude and inexact manner in which the art has hitherto been practiced. The comparatively small amount of scientific research that has been done on the problems and principles involved has not only justified itself in practice but furnishes abundant grounds for the expectation that a great deal more of valuable results will follow further work. It is not mere guessing to say that when advantage is taken of all that is known of improved salting methods a fish nearly if not quite equal in edible qualities to fresh fish is obtained, and in some cases the quality is decidedly improved by salting.

There is every reason to expect a good future for the salt fish industry, but progress must be made. Preservation by this method is eminently practicable, simple, and reliable for holding and transporting our sea fishes to the inland population.

1. A discussion of the principles involved in the preservation of fish by salt has been presented.

2. Salt possesses no inherently peculiar preserving qualities, but preserves food by extracting water.

3. The principle by which salt (and other soluble substances) in concentrated solution extracts water is called osmosis. Osmosis is the passage or interchange of liquids and solutions through membranes which are more or less permeable. The permeability of cell membranes in fishes appears to be affected by high and low temperatures. The presence in or absence from the salt of certain impurities, notably calcium and magnesium compounds, the treatment of the fish, and the staleness of the fish, are factors which govern the permeability and have an important bearing on the preservation of fish by salt.

4. Calcium and magnesium compounds in addition to retarding penetration cause a whitening and hardening of the fish. There are chemical reasons for looking upon this whitening and hardening by these compounds as undesirable.

5. The flavor of fish is often altered by the salting process. Calcium salts retained in the tissue increase the salty taste and make necessary a prolonged soaking out. Undesirable flavors of fishes from muddy waters may sometimes be removed by salting the fish.

6. Salt applied dry penetrates the fish more rapidly and effects a quicker cure with less danger of spoilage in warm weather.

7. There is a very material loss of protein material from fish during the salting process. This material probably arises from the decomposition products ordinarily unable to pass out of the cells but which are digested by autolysis, an internal destructive process.

8. Autolysis is increased by crushing, bruising, rough handling, pewing, elevated temperatures, low temperatures followed by a rise, and, in general by factors that increase cell permeability. It is