Laboratory Tests 



Several hundred chemicals and ccmbinations of chemicals were tested 

 in the laboratory to determine which showed suitable preserving proper- 

 ties. In these preliminary tests the various chemicals were mixed with 

 small quantities of salmon eggs in glass jars and the samples stored at 

 roOTi temperature. Observaiiions made at intervals eliminated most of the 

 chemicals from consideration because of lack of preservative action, 

 adverse effect on texture, or because excessive amounts of an expensive 

 chemical were required. After taking into account the cost of the 

 chemicals which gave promising results the list was reduced to only three — 

 sodium bisulfite, sodium benzoate, and sodium chloride. Large concentra- 

 tions of sodium chloride (salt) gave good preseirvation but the texture of 

 the eggs was adversely affected. About 2 percent salt is generally added 

 to the final diet of natchery fish so this amount could be added initially 

 to the eggs along with other preservatives to give possible additional 

 preservation. 



The laboratory experiments indicated that 0.5 percent sodium bisulfite 

 based on the weight of the eggs (0.5 pound of preservative per 100 pound 

 eggs) gave good preservation for several months. There was scsae indication 

 that with 2 percent sodium chloride present the bisulfite concentration 

 could be lowered to 0.2 percent. It was desirable to keep the bisulfite 

 concentration at as low a level as possible because of its tendency to 

 destroy thiamine. 



Pilot-Plant -5cale Tests 



Pilot-plant -scale preservation tests of several hundred pound lots of 

 salmon eggs were made in commercial salmon canneries both on Puget Sound, 

 Washington, and Ketchikan, Alaska, diiring the summer of 1950* The test 

 lots of eggs were preserved in 110- pound metal drums, in friction top 30- 

 pound "berry tins" and in hermetically sealed No. 10 cans. Eggs were put 

 up with sodium bis\xlfite, and with sodium chloride, using two formulae — 

 0.5 percent NaHSO^ and 0.2 percent NaHSOo with 2.0 percent NaCl. 



Those eggs treated with chemicals containing 2 percent salt had a 

 tendency, upon storage, to liquefy. The eggs stored in hermetically 

 sealed tinned containers kept especially well. When the non-hermetically 

 sealed containers were used, a small layer of mold formed in sane cases 

 and after prolonged storage some small amount of spoilage had taken place. 



Hatchery Fish Feeding Tests 



Feeding tests on natchery fish were carried out using salmon eggs 

 treated with various chemical preservatives. The purpose of these feeding 

 experiments was to determine the effect, if any, of these chemical additives 

 on hatchery fish. Feeding tests were started in April 1950. Hatchery fish 

 are available only in the early part of the year; however, at this time of 



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