How fillet quality changes in rainbow trout (Oncorhynchus mykiss) fed diets supplemented with barberry (Berberis vulgaris) fruit extract

The present study aimed to investigate the effect of barberry (Berberis vulgaris) fruit extract (BFE) on final product quality in rainbow trout (Oncorhynchus mykiss) during the refrigerated storage. Fish with an initial weight of ∼60 g were fed diets with different levels of barberry fruit methanol extracts: 0 (B0), 0.5 (B0.5), 1 (B1), 2 (B2) g/kg) for 10 weeks. At the end of the feeding trial, fillets were refrigerated for 21 days to monitor quality parameters at 1-week intervals. Fillet proximate and fatty acid composition did not significantly change between the treatments, while shelf life, color and sensory attributes were significantly affected by the experimental feeds (P<0.05). The total bacterial count ranged between 2.12 and 8.33 log CFU/g during the storage, decreasing with the increase in the dietary BFE level. Although pH was not affected by the dietary BFE level and the duration of storage, lipid peroxidation level was significantly influenced by the dietary treatments and the storage (P<0.05). The level of MDA increased with the increase in the duration of the storage reaching 7.86 µmol/kg in the control group on the day 21, but decreased with the increase in the dietary BFE (6.19 µmol/kg in B2). The a* value, which indicates redness, also increased with the dietary BFE level and reached the highest value (0.81) in the B2 group. Based on the sensory analysis, the fillet from the B2 diet fed fish was the most appreciated group, receiving the highest score in terms of all parameters. Our overall results suggest that BFE as a natural additive can be used in rainbow trout diet at 2 g/kg to improve coloration and overall appreciation of the fillet, and enhance the shelf life up to 2 weeks.