FISHERY BULLETIN: VOL. 69, NO. 



except for a small amount of suspended protein, 

 remained clear and colorless. 



The number of bacteria on the skin of the 

 salmon held in the untreated brine increased 

 more than 20 fold. After the salmon had been 

 in storage for 9 days, the number of bacteria 

 on the skin increased from its original value of 

 1.1 X lO'^ to 2.4 X lOVcm-. At 11 days of stor- 

 age, the salmon were judged, on the basis of 

 odor, to be spoiled. 



Swab tests on the skin of the salmon held in 

 the brine treated with CO2 showed that essen- 

 tially no growth of bacteria occurred during the 

 17 days of storage. 



Chemical Measurements 



pH. The pH of the brine was measured as 



was described earlier. The pH of the flesh was 

 not measured. Table 3 shows the pH values 

 for the brines. 



Except for the initial value of 7.1, the un- 

 treated brine had a pH of 6.8 throughout the 

 experiment. As yet, we do not know if the dif- 

 ference in pH of the brines used for holding 

 rockfish and salmon is related to a difference in 

 the spoilage patterns of the two species. 



The pH of the brine treated with CO2 re- 

 mained in a stable acid condition throughout the 

 experiment. 



CO2 concentration. — No analyses were made 

 for CO2 in the flesh or in the brine. However 

 CO2 was continuously metered into the experi- 

 mental brine at the same rate as that in the 

 experiment with rockfish. 



Salt concentration. — For greater accuracy 

 than is possible with the simple rapid method 

 of analysis described earlier, the concentration 

 of NaCl in the flesh was measured by the Vol- 

 hard method (Horwitz, 1960). The sample an- 

 alyzed was taken from both fillets of a single 

 fish. The fillets were mechanically comminuted 

 and thoroughly mixed before the sample was 

 taken, and the analyses were made in duplicate. 



As was true with the rockfish, treating the 

 brine with CO2 had no effect on the rate of salt 



uptake. Salmon held in both brines showed 

 progressive and similar increases in concen- 

 tration of salt to a maximum of 1.3 Sf to 1.4% 

 in the flesh at 9 days. 



SUBJECTIVE MEASUREMENTS 



Raw Salmon 



At each sampling, the salmon were examined 

 in the same manner as had been the rockfish. 



At the beginning of the experiment, the un- 

 treated salmon had a bright appearance and a 

 thick covering of colorless slime. After 4 to 5 

 days, however, they had lost their natural 

 brightness. They remained slimy, but the slime 

 had begun to turn yellow. By the 11th day, 

 the salmon looked blanched and smelled spoiled. 

 At this time, the brine was dark brown and 

 had an intense odor of spoilage. 



The salmon held in the brine treated with CO2 

 retained most of their natural color during the 

 experiment. By the end of the first week of 

 storage, however, only a trace of slime remained 

 on their skins. On the 18th day, when the ex- 

 periment was terminated, the salmon still had a 

 good appearance and were free of off odors. 

 The brine was almost colorless and almost odor- 

 less. 



Cooked Salmon 



The taste-test scores (Table 4) show that the 

 samples from both storage environments were 

 equally acceptable through the first 7 days of 

 storage. 



Table 4. — Sensory evaluations on the flesh of chum 

 salmon held in CO.^-treated refrigerated brine and in 

 untreated refrigerated brine. 



* A score of 10 denotes o product of highest quality; one of 5 denotes 

 a product of borderline quality. 



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