COLLINS ET AL.: BLACK ROCKFISH: CHANGES IN PROPERTIES 



were slightly lower. Although EPN did not change 

 significantly with time of fresh holding in ice and 

 only slightly in MRSW, the effect of the length of 

 time of fresh holding on EPN became apparent in 

 samples held at -18" C for 6 to 9 mo. If EPN is 

 related to the texture of black rockfish, the data in 

 Table 4 suggest that 6 mo of frozen storage at -18° 

 C was too long for minced flesh at any level of fresh 

 quality and that various periods of frozen storage 

 would give acceptable texture depending on the 

 level of fresh quality when frozen. 



The TMAO content of the unwashed minced 

 flesh was unaffected by time of holding in ice but 

 decreased slightly in MRSW (Table 5). Although 

 not expected to change with the frozen storage of 

 this non-gadoid fish, amine data were obtained 

 since no data on TMA and DMA and only one 

 value for TMAO (93 mg N/100 g, Dyer 1952) have 

 been reported in the literature for S. melanops. 

 There was a strong reduction in TMAO content of 

 the unwashed minced flesh with time of frozen 

 storage to 4 mo with little change thereafter. 

 TMA and DMA values were not affected by frozen 

 storage (data not included in tables). Con- 

 sequently, the substantial reduction in EPN was 

 not caused by formaldehyde. We cannot explain 

 either the observed loss of TMAO without a con- 

 comitant increase in either TMA or DMA content 

 or the lack of change in TMAO content with time 

 of frozen storage of the unwashed minced flesh. 



SUMMARY 



Black rockfish was held in the round in ice or 

 MRSW to 14 days. The yield of fillets was not 

 affected by time of holding but fish held in ice gave 

 slightly higher yields than fish held in MRSW, 32 

 and 31%, respectively. The usual chemical spoilage 

 tests (TMA, TV A, TVB) were of little or no use as 

 indicators of spoilage. Observations of the begin- 

 ning of off-odors, softness of flesh, and decomposi- 

 tion of viscera at 10 days were not confirmed by 

 sensory evaluation of the cooked portions. For this 

 species, early changes in quality were best judged 

 subjectively on the raw, whole fish and fillets. 

 Formal sensory evaluation was less sensitive than 

 informal evaluation to change in quality, and 

 chemical spoilage tests were not sensitive to obvi- 

 ously advanced spoilage. Washing the minced 

 flesh resulted in a reduction in salt, solids, and 

 TMAO content. The yield increased with washing 

 because of increased water content but when cal- 



culated on a salt-free, constant 18% solids basis, 

 the yield decreased in both systems to 28% when 

 minced and washed. The EPN values of minced 

 flesh from ice-held fish decreased during frozen 

 storage at -18" C from about 80 to 35% after 9 mo 

 and MRSW-held fish gave similar but slightly 

 lower EPN values. The degree of fresh quality 

 strongly influenced EPN values during frozen 

 storage indicating that the time of holding in ice or 

 MRSW should be considerably less than 10 days to 

 maintain good quality for any reasonable period of 

 frozen storage. 



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