REPPOND ET AL WALLEYE POLLOCK: CHANGES WHEN HELD IN SEA WATER 



decrease in quality was detected at 8 days in the 

 raw fillets, and at 6 days in the cooked fish. There- 

 fore, TVA could not be used as an index of spoilage 

 for pollock held in MRSW. 



In both lots, the TMA values (Dyer 1945) were 

 higher for ice-held fish than for MRSW-held fish 

 (Figure 2). A higher TMA content should have 

 occurred in the fish held in ice if their flesh was at a 

 higher pH because Castell and Snow (1949) 

 showed the rate of formation was higher in a more 

 basic medium. The pH of a 2:1 distilled water- 

 ground flesh mixture was 7.25 and 6.45 for ice- 

 held and MRSW-held fish, respectively, and 

 changed little with time of holding. Another 

 reason for the higher TMA content in iced fish was 

 that the lower pH of the brine should inhibit the 

 proliferation of bacteria. For fish held in MRSW, 

 there was little difference in TMA content be- 

 tween lots but for fish held in ice, values for Lot 2 

 are about twice the corresponding values in Lot 1. 

 This difference in TMA values between lots was 

 probably due to the fish in Lot 2 being iced in 



o 



2 



O 



2 



4 6 8 10 12 14 16 



TIME OF HOLDING DAYS 



Figure 2.— Change in trimethylamine (TMA) content of fillets 

 from walleye pollock with time of holding in ice and in modified 

 refngerated seawater (MRSW). 



layers while those in Lot 1 were individually iced. 

 Kramer et al. ( 1977) reported TMA values on iced 

 pollock that were similar to that of Lot 1 . Although 

 there was no statistically significant correlation 

 between flavor of iced fish and TMA content, the 

 rapid change in TMA content for iced fish from Lot 

 2 occurred at the same time as the flavor score 

 decreased. The change in rate of accumulation of 

 TMA in iced fish in Lot 1 was not as discernible but 

 probably occurred between 4 and 6 days. Kramer 

 et al. (1977) reported a large increase in TMA 

 content in pollock after 8 days in ice. Differences in 

 analytical technique, sample preparation, or icing 

 procedure could account for the different times for 

 the sudden increase in TMA. For MRSW-held fish 

 in Lot 2, no rapid change in TMA content was 

 noted even after the flavor scores decreased. Con- 

 sequently, TMA content may provide a useful 

 index of spoilage for ice-held pollock but may not 

 be usefull for fish held in MRSW. 



Using the modification by Tozawa et al. ( 197 1 ) of 

 Dyer's (1945) method for determining TMA has 

 reduced the interference from DMA but has not 

 always provided as reasonable or as useful data 

 (Botta and Shaw 1975; Shaw et al. 1977). Fish 

 from Lot 2 were analyzed by both methods and 

 though TMA values were generally lower using 

 the method of Tozawa et al., there was no differ- 

 ence in the way TMA content varied with time of 

 holding. Consequently, the methods of Dyer and 

 Tozawa et al. were equally useful as chemical in- 

 dices of spoilage for pollock during fresh storage in 

 ice. The TMA values as determined by the method 

 of Tozawa et al. were not included in this report. 



The TMAO content (Lot 2) of the zero holding 

 time sample was 69 mg N/100 g flesh. Tokunaga 

 (1964) has reported TMAO values which averaged 

 about 100 mg N/100 g flesh. The TMAO content of 

 the ice-held fish remained essentially unchanged 

 to 8 days but dropped to 36 mg N/100 g flesh on the 

 last day (Figure 3). The TMAO content offish held 

 in MRSW was about the same as that offish held in 

 ice to the fourth day then rapidly decreased. Al- 

 though there was no significant statistical correla- 

 tion between TMAO values and flavor scores, the 

 decrease in TMAO content coincided with the de- 

 crease in flavor scores for MRSW-held fish. The 

 TMAO content of the ice-held fish had not changed 

 significantly at the eighth day of holding even 

 though the flavor score had decreased sig- 

 nificantly. 



The DMA content was also determined on fish in 

 Lot 2 (Figure 4). The rate of accumulation of DMA 



485 



