February 15-18, 2009 Washington State Convention Center Seattle ...

SENSORY ANALYSIS OF RAINBOW TROUT Oncorhynchus mykiss FED PUFA-ENRICHED
BLACK SOLDIER FLY PREPUPAE
Wendy M. Sealey * , T. Gibson Gaylord, Frederic T. Barrows, Jeffery K. Tomberlin, Mark A. McGuire, Carolyn Ross
and Sophie St-Hilaire
Hagerman Fish Culture Experiment Station
University of Idaho
3059F National Fish Hatchery Road
Hagerman, ID 83332 USA
wsealey@uidaho.edu
Limited work has been done on the use of insects for fishmeal and fish oil replacement in rainbow trout diets, despite the fact
that insects make up part of their natural diet. A previous study in our laboratory indicated that black soldier fly prepupae could
be used to replace a portion of the fishmeal component of a practical grow-out diet without compromising growth. However, in
that study, sensory analysis of fillets was not performed. Therefore, the objective of this study was to determine the effects of
dietary inclusion of black soldier fly prepupae on rainbow trout fillet quality.
Black soldier fly prepupae were reared on dairy manure and enriched by supplementing fish offal to the growth medium during
the last month of culture. For the fish feeding trial, a practical-type trout diet was formulated to contain 40% protein with roughly
half of the protein derived from fish meal and the remaining from soybean meal, corn gluten meal and wheat meal. Four test
diets were developed by substituting 25% and 50% of the fishmeal component of the control diet with normal (BSF) or enriched
(EBSF) black soldier fly prepupae on a amino acid equivalents basis. Dietary fat content was adjusted to approximately 15%
lipid using fish oil and poultry fat to provide required levels of essential fatty acids and maintain approximately equivalent fatty
acid ratios between the treatments. Diets were fed to three replicate tanks of fish per treatment (15 fish/tank, mixed-sex House
Creek strain) for 8 weeks. Trout were reared in 140 L tanks supplied with 6 L/min of constant temperature (14.8°C) flowthrough
spring water. At the end of the feeding trial, three fish per tank were sampled for determination of hepatosomatic index,
intraperitoneal fat ratio and muscle ratio. The muscle portion obtained was subsequently utilized for determination of proximate
and fatty acid composition. Fish remaining after sampling were pooled by tank, euthanized and immediately transported on ice
to a commercial fish processing facility. At the processing facility, fish were individually hand-filleted as gourmet fillets with
ribs and pin bones removed. Following filleting, samples were pooled by tank and stored at -20C until shipment (approximately
1 week) to Washington State University for sensory evaluation.
Growth of fish fed the EBSF diets was not significantly different from those fish fed the fish meal-based control diet while
growth of fish fed the BSF diets was reduced as compared to the control diet. Muscle ratio was not altered by diet but control
fish had significantly higher IPF than those fish fed the EBSF or BSF diets. A group of 30 untrained panelists did not detect a
significant difference in a blind comparison of fish fed the fish meal containing control diet as compared to fish fed the EBSF
or BSF diets. These data suggest that EBSF can be used to replace up to 50% of fishmeal portion of a practical trout diet for 8
weeks without significantly affecting growth or sensory quality of rainbow trout fillets.
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