REPPOND ET AL : WALLEYE POLLOCK CHANGES WHEN HELD IN SEAWATER 



Friedemann and Brook 1938), total volatile base 

 iTVB, Stansby et al. 1944), and extractable pro- 

 tein nitrogen (EPN.Dyeretal. 1950). Analyses for 

 formaldehyde I FA, Castell and Smith 1973), 

 trimethylamine oxide (TMAO, Bystedt et al. 

 1959), free «-amino-nitrogen (Pope and Stevens 

 1939), and nonprotein nitrogen (NPN, Nikkila 

 and Linko 1954) were carried out on a 5'/ 

 trichloroacetic acid extract. An aliquot of the ex- 

 tract was neutralized and analyzed for di- 

 methylamine (DMA) by Dowden's (1938) method 

 modified by increasing the time of extraction to 15 

 min and by using a mechanical shaker. Analysis 

 for trimethylamine (TMA) in fish in Lot 1 was 

 carried out using Dyer's original method (Dyer 

 1945). For fish in Lot 2, Dyer's method and the 

 modification by Tozawa et al. (1971) were used. 



RESULTS AND DISCUSSION 



Physical Appearance and Yield 



Changes in odor, degree of decomposition of vis- 

 cera, and physical appearance of fish from Lot 1 

 and Lot 2 occurred at the same time of holding. 

 Ice-held fish were generally free of slime whereas 

 fish held in MRSW were covered with a thin layer 

 of slime throughout the experiment. After a few 

 days, the gills and fins offish held in ice were firm 

 but those in MRSW were soft and swollen. After 4 

 days in ice, the pollock had soft livers and after 6 

 days, decompostion of the viscera could be detected 

 externally. Softening of fillets became noticeable 

 in 2 or 3 days in fish from both holding systems. An 

 unpleasant odor became noticeable after 3 days in 

 ice and predominant after 4 days. Browning of the 

 fillets appeared after 6 days in ice and seemed to be 



enhanced by grinding. Based on this informal sub- 

 jective observation on the physical appearance 

 and odor of the fish in the round and the raw fillet, 

 pollock could be held a maximum of 4 days under 

 ideal icing conditions before becoming unaccept- 

 able for human consumption. 



Pollock held in MRSW showed the same 

 changes as those held in ice but they occurred 

 several days later. The maximum time the fish 

 could be held in MRSW and still be acceptable for 

 consumption was 8 days based on evaluation of the 

 fish in the round and the raw fillets. The amine 

 odor usually associated with deterioration of fish 

 was not present but there was a distinct and un- 

 pleasant smell in the fillets offish held more than 

 12 days in MRSW. The changes in odor and tex- 

 ture occurred gradually in fish from either system, 

 so the exact time for onset of spoilage based on 

 these informal, subjective evaluations could not be 

 reliably determined. 



Pollock held in either medium gained weight 

 steadily throughout the experiment (Table 1 ). The 

 increase was more than 6% of the initial weight 

 after 5 days in MRSW but only 3V( in ice. The yield 

 of fillets averaged 36% in both media and re- 

 mained fairly constant. Solids content of the flesh 

 decreased from IS'i initially to 16% and 17'r after 

 10.5 days in ice and in MRSW, respectively (Table 

 1 ). Solids contents of fish in Lot 2 were similar. The 

 higher solids content of fish held in MRSW was 

 probably caused by the uptake of salt (Table 1). 



Sensor}' Assessments 



Differences in odor and firmness were highly 

 noticeable in raw fillets from fish held different 

 lengths of time in the same holding system or 



Table l. — Change in weiglit, salt, and total solids content of fillets and washed ground flesh of walleye pollock iLot li with time of 



holding in- ice and in modified refrigerated seawater. 



'Total round weight of the fish that composed the sample 



^Weight of ground, washed flesh if no portion had been reserved for analysis of fillets. 



483 



