Effects of Methanolic Pomegranate Peel Extract on the Chemical, Sensory, Textural, and Microbiological Properties of Gutted Rainbow Trout (Oncorhynchus mykiss) during Frozen Storage

The effects of methanolic pomegranate peel extract (MPPE) on the quality of gutted rainbow trout (Oncorhynchus mykiss) were examined periodically during 6 months of storage at -18 degrees C. Fresh samples were dipped (ratio of fish to liquid, 1:2 [wt/vol]) in sterile water or in sterile water containing 1, 2, or 4% (wt/vol) MPPE and packed in low-density polyethylene pouches. The control and treated samples were analyzed monthly for microbiological, chemical, sensory, and textural characteristics. Microbial growth in samples was significantly reduced by MPPE treatment (P < 0.05). Smaller increases in the values for total volatile base nitrogen, peroxide, and thiobarbituric acid reactive substances and better oxidative stability were also obtained. Moreover, higher organoleptic scores were recorded. However, regarding the general acceptability, the highest score was achieved in the 1% MPPE group. Greater hardness and chewiness were obtained with 4% MPPE (P < 0.05). Therefore, dipping fish in MPPE can be considered an effective method to extend the shelf life and the overall quality of the product.