Date of Award:

1980

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Nutrition, Dietetics, and Food Sciences

Department name when degree awarded

Nutrition and Food Sciences

Advisor/Chair:

Von T. Mendenhall

Abstract

Three non-gadoid fish species, trout (Cynoscion regalis), English sole (Paraophyrys vetulus) and Pacific red snapper (Scomber i~onicus) have been tested for the recovery of trimethylamine oxide (TMAO), trimethylamine (TMA), dimethylamine (DMA), and formaldehyde (FA) during postmortem storage at 4°C and -S°C. TMAO, TMA, and DMA content was determined by measuring them as the salt derivative of picric acid. FA was determined by using the 3-Methyl-2-Benzothiazolinone hydrazone test.

In muscle tissue of red snapper and English sole, it was clear that initially TMAO decreased during storage at 4°C, while the amounts of TMA, DMA, and FA increased. When these species were stored at -S°C, only a slight decrease . in the amount of TMAO was measured. Less TMA was formed at -S°C than at 4°C. There was no DMA production in these two species at -S°C and the amount of FA that was formed was significantly less (p < 0.05) than that formed when the storage temperature was 4°C. In the muscle tissue of the trout, no TMAO, TMA, nor DMA was recovered at both storage temperatures. There was no significant difference (p < 0.05) between the amounts of FA recovered from the trout stored at both storage temperatures.

The amount of FA recovered from all of the species decreased significantly after 7 days at 4°C and 50 days at -5°C. FA values may be used as an indication of freshness in those fish species which do not produce TMA during storage. TMA was not produced in the tissue of the English sole and the red snapper during frozen storage. No TMA was recovered from the tissues of the trout stored at 4°C and -5°C. In order to obtain reliable data, FA values would have to be determined for each species and each storage condition. FA values would only be reliable if measured before incipient spoilage takes place (7 days at 4°C and 50 days at -5°C). When TMA is produced in fish tissue, the measurement of it combined with organoleptic evaluation would be a more useful tool than FA value in evaluating fresh saltwater fish, both gadoid and non-gadoid species, during refrigerated storage.

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