Proximate Composition, Retained Water, and Bacterial Load for Two Sizes of Hybrid Catfish ( Ictalurus furcatus × Ictalurus punctatus ) Fillets at Different Process Steps.

The catfish processors in the US are required to state the maximum percentage of retained water content (RWC) on the product label. The objectives of our study were to quantify the RWC of processed hybrid catfish fillets from proximate composition and the bacterial load at different processing points. Water content was determined using oven-dry (AOAC950.46,1990) and Near-infrared (NIR) spectroscopy. Protein and fat content were determined by NIR spectrometer. Psychrotrophic (PPC) and Total Coliform (TCC) counts were enumerated using 3MPetrifilm TM . The fillets' overall baseline water, protein, and fat content were 77.8, 16.7 and 5.7%, respectively. The RWC of final fresh and frozen fillets were ~1.1=/- 2.0% (not significant) and ~4.5%, respectively, and was not fillet size or harvest season dependent. Baseline water content (78.0 vs. 76.0%) was higher ( p ≤ 0.05), and fat content (6.0% vs. 8.0%) was lower ( p ≤ 0.05) for small (50-150 g) compared to large fillets (150-450 g). Higher ( p ≤ 0.05) baseline PPC (~4.2 vs. ~3.0) and TCC (~3.4 vs. ~1.7) were observed for the warm season (April-July) fillets compared to the cold season (Feb-April). This study provides information to processors and others on estimating retained water and microbiological quality of the hybrid catfish fillets over the process line.