Page:Principles preservation fish by salt.djvu/28

22 retarded or arrested by continued low temperatures, sufficiently high temperatures, and by salt.

9. The damage done by autolysis appears to be in large part preventable.

10. Fish containing blood, or otherwise not well cleaned, spoil at a lower temperature than those thoroughly cleaned and freed from blood. Thoroughly cleaned fish may be salted at from 90 to 100° F. if pure salt is used.

11. A method of curing fish embodying the improvements cited was tried in Florida on a small commercial scale with gratifying success.

12. Scotch-cured herring develop a peculiar flavor which is derived from the fermented or otherwise altered blood. This method has for its aim an alteration to suit particular tastes, while other methods of salting discussed aim at the preservation of the fresh qualities of fish.

13. There are reasons for expecting that the improvements made in the salting of other fish, particularly those which depend on the use of a very pure salt, will find application in the mild curing of salmon.

14. Fats undergo certain changes after the fish is salted, resulting in a condition known as "rusting." Rusting consists of oxidation of fat after the latter has been split into free fatty acids. This splitting is caused by tissue enzymes in the presence of warmth and moisture. Oxidation is brought about through the agency of light in the presence of water. While rusting causes large losses of fish, the means of preventing it, such as tight barrels, air-tight covering, and cool dark storage, are not very satisfactory. The problem demands further investigation.

15. Fishes whose flesh is not fat and therefore not prone to rust are subject to damage by reddening. Reddening is caused by two organisms, a spirochaete and a bacillus. They may be destroyed by fresh water or live steam. They originate probably in solar sea salt and are apparently not found in mined salt or other purified American salt.

16. Some work has been done toward the development of a process for recovery of salt and other valuable materials from brine. There are a number of promising possibilities which should make this an attractive field for chemists and engineers.

17. Certain substances are sometimes used as adjuncts in salting fish. Saltpeter preserves a pink color and neutralizes hydrogen sulphide. Boric acid is used for preserving cod against reddening. Sodium hypochlorite has been proposed as advantageous in conjunction with salt. It may be produced electrolytically from sea water.

18. The size and shape of the fish influences the rate of penetration of salt into it. Certain mechanical methods of forcing brine into large fish may be advantageous.