| Summary: | Commercially available sunflower meal (SFM) was subjected to extrusion processing and then tail-end dehulling (using multiple vibrating screens) to nutritionally upgrade the protein content to 40.9% on a dry weight basis (db) and improve its digestible energy content. A basal and four test diets were formulated by replacing fishmeal protein in the dietary mix with increasing equal increments of nutritionally upgraded SFM (maximum dietary concentration 27%; db). The resulting five diets (-49% protein and -18.5% lipid; db) were fed to fifteen groups of post-juvenile Atlantic salmon (n=50/group; 3 groups/diet) over an 84-day period. The performance of Atlantic salmon (initial mean weight - 116 g) was judged by the following parameters: weight gain, specific growth rate, feed intake, feed efficiency, protein efficiency ratio, percent protein deposited, gross energy utilization, and percent survival. Also, proximate analyses of both whole bodies and muscle samples (fillets) were undertaken on salmon from day 0 and 84. Atlantic salmon fed the basal diet (0% SFM) and the four test diets (contained SFM) did not differ significantly (p > 0.05) with respect to any of the preceding performance parameters. To determine the effect of using SFM in the diet on the flesh quality attributes of Atlantic salmon, sensory evaluation (14 panelists) was conducted over 9 sessions (after 4 one-hour training sessions) to test salmon quality attributes of aroma, flavor, foreign flavor and texture, using a descriptive sensory ballot. Sensory panel results indicated that salmon - aroma, flavor and texture were similar (p > 0.05) across the five diets. However, fillets from salmon fed diets A (0% SFM) and E (27.1% SFM) and diets B (6.8% SFM) and E were significantly (p < 0.05) different, in perceptible foreign flavors, respectively. Salmon fillet color, quantified using Salmofan™ and Hunter Lab L, a and b scores, did not differ (p > 0.05) across the diets. In addition, Salmofan™ scores were positively correlated (r = 0.86) with Hunter (a) scores. Headspace gas chromatography (GC) of volatile compounds collected with solid phase micro-extraction fibers (SPME) was conducted using cooked salmon fillets. Results from GC were analyzed by the principal component similarity (PCS) technique and they further corroborated those obtained from foreign flavor analysis by a sensory panel. In conclusion, the incorporation of ≤ 27.1% of SFM in the basal diet by partial replacement of premium quality fishmeal resulted in no adverse effects on growth of Atlantic salmon reared in seawater. But foreign flavors perceived by panelists were significant (p < 0.05) in the fillets from salmon fed diet E (27.1% SFM). Hence, the highest dietary SFM concentration used in the present study appeared to contribute towards some foreign flavors in the flesh, but further research is needed to confirm and possibly extend this finding if higher dietary concentrations of SFM are employed. Land and Food Systems, Faculty of Graduate
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