COLONS ET AL BLACK ROCKFISH: CHANGES IN PROPERTIES 



higher from fish held in ice than from fish held in 

 MRSW, 31.7% and 30.5%, respectively. When 

 yield data are converted to a salt-free, 18% solids 

 basis however, equal yields of fillets were obtained 

 in both systems (34%). The solids content of the 

 fillets decreased slightly in ice but increased in 



MRSW because of the increase in salt content (Ta- 

 ble 1 ). The absorption of salt from the MRSW sys- 

 tem is not a problem because rockfish have thick 

 flesh and skin. 



Sensory Evaluation 



Table l. — Initial round weight and change in yield, salt, and 

 total solids content of fillets and washed ground flesh from black 

 rockfish (Lot 1) with time of holding in ice and in modified 

 refrigerated seawater. 



'Total round weight of fish that composed the sample 

 ^Yield ot washed ground flesh if no portion had been reserved for analysis of 

 fillets 



Table 2. — Change in mean sensory analysis scores ± standard 

 deviations for baked portions of blocks of fillets from black 

 rockfish (Lot 21 with time of holding in ice and in modified 

 refrigerated seawater (MRSW). Panel had 12 judges. Flavor 

 and texture scores were on the following scale: 5-Very good. 

 4-Good, 3-Fair, 2-Borderline. and 1-Poor. Preference scores 

 were on a 9-point scale: 9-Like extremely. 8-Like very much, 

 7-Like moderately, 6-Like slightly, 5-Neither like nor dislike. 

 4-Dislike slightly, 3-Dislike moderately, 2-Dislike very much, 

 and 1-Dislike extremely. 



holding 

 (days) 



Ice 



MRSW 



Ice 



MRSW 



MRSW 



3.5±0.7 

 3.1 ±0.4 3.8±0.6 

 34±07 3.6-0.5 

 36±06 2.9±0.8 

 3.5±0.8 3.13:0.5 



4.1: 

 3.9±0.7 

 4 1 ±0.5 

 4.3±0.5 

 4.0±0-5 



0.6 



4.1 ±0.3 



4.0±0-4 



3.8±0.6 



3.8±0-6 



6.3 ±1.4 

 5.8±0.7 6.4±13 

 6.3±12 63±09 

 6.5±1.0 5,2±13 

 6.4±13 5.4±1 2 



No significant (P<0.05) change in flavor, tex- 

 ture, or preference was noted between the zero 

 time control and any sample from either holding 

 system (Table 2). No significant differences in sen- 

 sory scores occurred among the ice-held samples 

 but the differences in flavor and preference scores 

 between samples held 3 days and 8 days in MRSW 

 were significant. However, these differences were 

 probably circumstantial since neither the 3- nor 

 8-day MRSW sample differed from any of the other 

 samples from that holding system. 



The bland flavor of rockfish flesh was reflected in 

 the preference scores which ranged from "like 

 slightly" to "neither like nor dislike." The sensory 

 data indicate that when held in ice or in MRSW 

 this species of rockfish will maintain its accepta- 

 bility during commercial holding periods of at 

 least 8 to 10 days. 



Chemical Analyses 



The protein content of fillets (Table 3) was unaf- 

 fected by time of holding but was slightly lower 

 from fish held in ice than in MRSW. The nonpro- 

 tein nitrogen content decreased slightly with time 

 of holding in both holding systems. 



Several chemical tests were performed to mea- 

 sure spoilage. TVA values increased from 0.07 at 8 

 days in ice to 0. 10 meq/100 g at 10 days which may 

 indicate a change in quality at 10 days. No change 

 was noted in fillets from the MRSW system. TVB 

 values were constant and low (about 4 mg N/100 

 g). As with walleye pollock, TVB data were not 

 useful to indicate spoilage. TMA values increased 



Table 3. — Change in analytical values of fillets from black rockfish (Lot 1) with time of holding in ice and in modified refrigerated 



seawater. 



Time of 

 holding 

 (days) 





 4 

 6 

 8 



10 



12 

 14 



Protein' 

 (%) 

 18,3 

 18-5 

 188 

 183 

 184 

 182 

 18.4 



Ice 



TVB 



NPN TVA (mgN: 



(%) (meg H-'IOOg) lOOg) 



0.34 

 0.33 

 31 

 31 

 31 

 030 

 0.30 



06 

 006 

 006 

 007 

 10 

 Oil 

 0.10 



3-9 

 3.6 



TMA 



(mg N: 

 lOOg) 



020 

 041 

 041 

 049 

 0,59 

 62 

 0.82 



DMA 



(mg N,' 

 lOOg) 



020 

 30 

 0,24 

 27 

 029 

 0.30 

 0.24 



Protein' 

 (%) 



18.3 



18 8 

 190 

 19.0 

 19.2 



19 1 

 19.0 



Mo dified re frigerated seawater 



^ ' ' " TVB TMA 



NPN TVA (mg N; (mg N,' 



(%) (meqH-'IOOg) 100 g 100 g) 



0-34 

 032 

 0-31 

 030 

 0-30 

 0-30 

 0-27 



006 

 06 

 07 

 06 

 06 

 07 

 0-08 



39 

 33 



28 

 29 



20 

 37 

 43 

 49 

 56 

 67 

 069 



DMA 



(mg N/ 

 100 g) 



020 

 023 

 023 

 29 

 18 

 037 

 29 



867 



