UBC Theses and Dissertations
Effect of spoilage and processing conditions on the nutritive value of various marine protein sources for rainbow trout (Oncorhynchus mykiss) and chinook salmon (Oncohrynchus tshawytscha) Clancy, Gordon Sean
This study was undertaken to assess the nutritional value of fish meals (Pacific herring, Clupea harengus pallasi) and protein hydrolyzates (ocean perch, Sebastes alutus) processed in different ways for chinook salmon (Oncorhynchus tshawytscha) in salt water and for rainbow trout (Oncorhynchus mykiss) in fresh water. Three levels of raw material freshness (fresh frozen, moderately spoiled and highly spoiled) and two processing temperatures (low and high) were employed in the present study. Spoilage of Pacific herring stored at 2-5°C, as determined by the levels of total volatile nitrogen(TVN) and trimethylamine(TMA), was slow for the initial 8 days but increased rapidly until day 15. The direct distillation method with MgO yielded significantly higher TVN values than the microdiffusion method with K₂CO₃ or KOH and the steam distillation method with NaOH. The TMA values also varied with the method employed. For the routine determination of TVN and TMA microdiffusion with K2CO3 is recommended. The levels of putrescine and cadaverine in herring also increased rapidly after 8 days of storage at 2-5°C. Histamine levels remained low ( 8 days for herring and ocean perch stored at 2-5°C) before processing resulted in depressed digestibility values in both rainbow trout and chinook salmon.
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