Six different published methods of determining TVB-N were evaluated for accuracy, precision, suitability as an index of quality, and both cost and speed of determination, using gutted Atlantic cod stored in ice for up to 18 days. Although the method of determination affected the actual values obtained, it did not affect the overaIl relationship between TVB-N and sensory assessment of raw or cooked fish. The method of determination also affected .precision and both cost and speed of determination. If high operational costs could be tolerated, MgS04 ext/steam distillation would be the preferred method but if variability of results could be tolerated, TCA extraction/steam distillation would be the method of choice.
A controlled study to assess effect of method of catching and time of season upon blood clot, color, discoloration/bruising, odor, texture and final overall grades of fresh raw cod, muscle pH of thawed cod, and firmness (shear-compression force) of cooked muscle was conducted. Sensory analyses revealed that method of catching significantly (P 5 0.001) affected only color, discoloration/bruising, and final overall grades. Time of season did not significantly affect any sensory variables. Muscle pH was significantly (P 5 0.001) affected by both method of catching and time of season. Any significant effect of time of season upon firmness of cooked cod muscle depended upon method of catching. In general, method of catching was the most important factor affecting sensory quality of fresh raw Atlantic cod.
A portable instrument was developed to rapidly and objectively determine texture (firmness and resilience) of raw Atlantic cod (Gadus morhua) fillets. A controlled study determined the texture of raw fillets from 774 cod, caught at three different times of year. Compared to texture grades of fillets assessed by trained and experienced Fish Inspection Officers, this instrument was a dependable method of rapidly determined texture of raw fillets.
Roundnose grenadier (Coryphaenoides rupestris) was stored in ice in order to investigate changes in chemical and sensory characteristics. Analyses indicated that the keeping time of at least 18 days was better than that of most species of whitefish. Total lipid and free fatty acid concentration did not significantly change during iced storage. Inosine monophosphate, inosine, hypoxanthine, iodine number, peroxide value, thiobarbituric acid value, trimethylamine content determined by the Tozawa method, trimethylamine content determined by the Dyer method, moisture content, and pH all significantly (P < 0.05) changed during iced storage. Both peroxide and iodine values appeared to have potential as indicators of sensory quality. Trimethylamine concentrations, determined by both methods, were similar throughout the iced storage study.
1978. Effect of double freezing and subsequent long-term tefrozen storage at -23"C on the quality of inshore male capelin (Mallotus villosLts). J. Fish. Res. Board Can. 35: 452-456.Whole inshore male capelin (Mallotus villosus) were stored at -23"C for 2mo (C2), or 6 mo (C6) prior to thawing, beheading and eviscerating, and refreezing. Though the quality of the twice-frozen product was in both cases inferior to a once-frozen sample, it lvas still quite acceptable after 2yr of refrozen storage. As expected, quality was superior in the C2 samples, but in both sets of samples taste deteriorated to a sreater extent than texture. Chemical measurement of peroxide vilue indicateci a possible dlvelopment of rancidity that could not be detected by sensory analysis. Considerable lipid hydrolysis occurred, with the free fatty acids (FFA) at least doubling during storage; increases were greater in C6. tn both experiments FFA production correlated with texture, taste, and with extractable protein nitrogen (EPN). Dimethylamine (DMA), trimethylamine (TMA), hypoxanthine, and EPN appeared to be good indicators of storage time and sensory quality. Key words: capelin, dimethylamine (DMA), extractable protein nitrogen (EPN), free fatty acids (FFA), hypoxanthine, peroxide value, refrozen storage, taste, texture, trimethylamine Boru, J. R., aNo D. H. Surw. 1978. ElTect of double freezing and subsequent long-term refrozen storage at -23'C on the quality of inshore male capelin (Mctllotus villosus). J. Fish. Res. Board Can. 35: 452-456.
Male capelin (Mallotus villosus) from a spawning inshore stock were held whole in block frozen format −23 °C without the benefit of special protective treatments. The results indicated an exceptional storage life of the samples, with no development of oxidative rancidity as monitored by organoleptic analysis, although TBA data did indicate this possibility. For many variables, the major chemical and sensory changes appeared to occur as a result of freezing and thawing, rather than as a result of frozen storage; changes were fastest during the first 6 wk. Because of the high sensory scores, it was difficult to correlate most chemical tests and organoleptic changes, though the relationship of texture scores to EPN and FFA values was significant [Formula: see text]. Sensory analyses showed that, after 2 yr, the samples were still fully acceptable.
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