Graduate Thesis Or Dissertation

Effect of washing on the quality, desirability and stability of drum-dried machine separated rockfish flesh

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  • The effect of washing machine separated rockfish flesh on composition, quality and desirability was investigated. Washing machine separated rockfish flesh resulted in a 36.88% loss of solids. The greatest reductions were found in the ash (80.32%) and lipid (65.13%) levels in the washed flesh. Most of the sarcoplasmic proteins were lost during washing and only 77.29% of the protein (N X 6.25) was recovered. Washing the machine separated fish flesh did not appreciably alter the amino acid composition. The content of essential amino acids of the drum-dried treatments was similar to casein and this was reflected by the high protein efficiency ratios compared to the casein reference. The mineral composition of the unwashed machine separated flesh was similar to that of the fillet. Washing the machine separated flesh greatly altered the mineral composition in the flesh. The levels of calcium, magnesium, barium, strontium, boron, and manganese were not appreciably altered by washing. Phosphorus, potassium, and sodium levels were reduced while the iron, copper, zinc and chromium levels were increased in the washed flesh. The rapid formation of trimethylamine (TMA) in the drumdried rockfish fillet and unwashed machine separated flesh treatments may be related to the development of off-odors and off-flavors formed during storage at 30°C. The over-all desirability of bland wafers consisting of 10% drum-dried washed flesh increased slightly during storage but was not appreciably higher than the wafers containing the drum-dried fillet and unwashed fish flesh. Over-all desirability may not be directly linked to the formation of trimethylamine (TMA) since washing drastically reduced the level of trimethylamine oxide (TMAO) in the washed flesh and the subsequent formation of trimethylamine (TMA) during storage at 30°C. The much higher levels of malonaldehyde found in the drumdried washed machine separated rockfish flesh may implicate the oxidation of the lipids as being responsible for the lower over-all desirability of the washed flesh. The rapid formation of malonaldehyde may also indicate that naturally occurring antioxidants are leached from the flesh during the washing process.
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