FISHERY BULLETIN; VOL, 77, NO. 4 



1.8 kg/fish for an 1 1-fish sample at holding periods 

 of 0, 4, 6, 8, 10, 12, and 14 days. When removed 

 from the holding systems, the fish were washed 

 briefly to remove slime or ice, drained on a rack for 

 5 min, and individually weighed. The fish were 

 filleted by hand and the fillets were rinsed briefly, 

 drained on an inclined screen for 5 min, and 

 weighed. Notes were made on the appearance of 

 the round fish and the condition of the gills, vis- 

 cera, and fillets. The fillets were ground using the 

 coarse blade of an Oster^ food grinder, and a por- 

 tion was washed with cold water ( 1 part flesh: 2 

 parts water) for 15 min on a reciprocating shaker. 

 The flesh was drained for 30 min on an inclined 

 16-mesh plastic screen then weighed. Composite 

 portions of both washed and unwashed meats were 

 frozen at -34" C for chemical tests. Other portions 

 were sealed in polylaminated pouches and stored 

 at -18° C for 2, 4, 6, and 9 mo. 



Sensory 



Lot 2 fish ( 184 fish, 258 kg) were used for formal 

 sensory testing and were caught in the same loca- 

 tion 1 mo later, on 26 August. These fish were held 

 in ice and in MRSW in the same manner as Lot 1 

 and at 0, 3, 6, 8, and 11 days were filleted. The 

 fillets were packed into blocks and held at -34 C 

 for sensory evaluation several months later. The 

 blocks were sawed into portions measuring 80 x 

 50 X 12 mm and thawed at room temperature. The 

 control sample and samples from fish held in ice 

 were salted by immersion in a 5% solution for 1.5 

 min to minimize differences in salt content with 

 samples from fish held in MRSW. The portions 

 were cooked in individual sealed aluminum pans 

 at 232° C for 20 min in a commercial oven. Because 

 of the difficulty in equalizing the salt content, 

 samples from the two holding systems were not 

 directly compared. The results of the sensory test 

 were evaluated by analysis of variance. If analysis 

 of variance indicated a change had occurred with 

 time of holding, the Student-Newman-Keuls test 

 was used to determine which samples were differ- 

 ent. 



Analyses 



The frozen samples for chemical tests (Lot 1) 

 were tempered overnight in a refrigerator at 3° C 



^Reference to trade names here does not i mply endorsement by 

 the National Marine Fisheries Service, NOAA. 



and ground twice using the fine blade of an Oster 

 food grinder. Analyses were carried out for total 

 nitrogen, total solids, chloride (Horwitz 1975: 

 15, 309, 310), total volatile acid (TVA, 

 Friedemann and Brook 1938), total volatile base 

 (TVB, Stansby et al. 1944), and extractable pro- 

 tein nitrogen (EPN, Dyer etal. 1950). Analyses for 

 trimethylamine oxide (TMAO, Bystedt et al. 

 1959), nonprotein nitrogen (NPN, Nikkila and 

 Linko 1954), and trimethylamine (TMA, Tozawa 

 et al. 1971) were carried out on a 5*^ trichloroace- 

 tic acid extract. An aliquot of the extract was neu- 

 tralized and analyzed for dimethylamine (DMA) 

 by Dowden's method ( 1938 ) modified by increasing 

 the time of extraction to 15 min on a mechanical 

 shaker. 



RESULTS AND DISCUSSION 



Physical Appearance and Yield 



At each period of sampling, informal subjective 

 observations were made on the whole fish and 

 their raw fillets. We noted differences in gills, fins, 

 and slime between the two holding systems. In ice, 

 the gills were bright red to day 6 but discolored 

 quickly in MRSW. Cloudiness of the eyes started 

 at day 8 in ice but the eyes were white in a day or 

 two in MRSW. The beginning of off-odors in the 

 fillets, softening of flesh, and gut decompostion 

 was observed in both holding systems at 10 days 

 and worsened thereafter. At day 14, the odor of the 

 fillets was objectionable and mincing intensified 

 the odor. The quality of fillets from the fish held in 

 MRSW were generally judged better than from 

 fish held in ice for the same time. As noted later in 

 this paper, neither formal sensory nor chemical 

 tests detected the changes observed on the 10th 

 day of holding in ice or MRSW. Chemical tests 

 could not confirm the poor raw quality at 1 2 and 14 

 days which was so obvious that we would not serve 

 these fillets to a taste panel. Consequently, we 

 concluded that experienced observers could sub- 

 jectively judge the various stages of raw quality, 

 namely: good quality (0-8 days), onset of spoilage 

 ( 10 days), and unacceptable quality (12 days). 



Whole fish gained weight with time of holding in 

 either system ( Table 1 ). Fish held for 14 days in ice 

 gained half as much weight as those held in 

 MRSW, about 3'7f and 6<7f , respectively. The yield 

 of fillets increased slightly with time of holding in 

 ice but was constant with time of holding in 

 MRSW. The average yield of fillets was slightly 



866 



