Page:Principles preservation fish by salt.djvu/26

20 dry salt may be better. The experience gained in the work already done indicates that the recovery of valuable material from brine would not go well as a part of a small fish business but, having its own peculiar problems, would be more properly conducted as a separate business. In any event, this promising subject is commended to the chemists and engineers for study. We can not doubt that a few years will bring forth a complete solution of the problem of recovering things of value from brine that will make us wonder why we ever threw it away.

Various other chemicals are sometimes used in salt or along with it for various purposes. Some of these will be briefly discussed.

Saltpeter performs two functions in brine for the preservation of meat, namely, it combines with the red substance of blood, hemoglobin, which is unstable, to form a permanently stable red derivative, nitroso-hemoglobin. By virtue of its oxidizing power it may also oxidize hydrogen sulphide into sulphur dioxide and water; that is, a very foully odoriferous stuff to a substance which both bleaches and sterilizes. Saltpeter is, however, little used in curing fish, for the red color is undesirable, and hydrogen sulphide is rarely troublesome.

Boric or boracic acid is sometimes added to the final application of salt to dried salt cod. This is to prevent reddening. Undoubtedly it does do so, and undoubtedly most of it is removed from the fish when the latter is soaked up before cooking. Nevertheless, it seems that the end of this practice is not distant. Boric acid has long ago been condemned as a food preservative. With the comparatively small amount of scientific investigation that has already been done we have reason to hope that not only can reddening be prevented, but that by the general refinement and improvement of methods it will become unnecessary to use artificial preservatives to prevent reddening.

A method of promoting the preservation of fish by salt by the aid of sodium hypochlorite along with the salt has been patented. The original idea, it is understood, was to decompose the salt in sea water by electrolysis, sodium hypochlorite being formed. It was claimed that the sodium hypochlorite penetrates faster than ordinary salt. This substance contains some oxygen that may be given off to act as a sterilizing agent, and after the oxygen is given off ordinary salt or sodium chloride remains. What advantages the process possessed are not altogether apparent, for nothing appears to have come of it. It may be said, however, that sodium hypochlorite readily destroys urea, so that this substance might be advantageous in the preservation of grayfish and sharks but is unstable and must be used as soon as it is made.

The size and shape of the fish obviously have much to do with the time required for salt to penetrate through. Salt effects no preservation of parts until it reaches them. A thick fish may spoil, while a thin fish may be saved; hence the splitting of fish. Other methods of applying the salt to the inner parts of fish may be used, such as a needle syringe, whereby the brine is forced into the tissues, and compressed air, which is used to force brine into fish after the excess air has been removed from them in vacuo. It should also be possible