An assessment of red fillet prevalence in the catfish industry

Abstract

Nonstandard Channel Ictalurus punctatus and Hybrid I. punctatus × I. furcatus Catfish fillets are rejected by catfish processors primarily due to aberrations in muscle texture or coloration (i.e., yellow, pink, red), and represent an economic loss for both the processer and farmer. Of these fillet types, red fillet is characterized by red coloration, with affected areas ranging from a solitary spot to the whole fillet. The present study investigates the prevalence of red fillet within the catfish industry and evaluates compositional differences in fillets by means of color, proximate composition, and microbial presence between red (diffuse red patch), punctured (singular red spot), and acceptable fillets. Red fillets with presence of different bacteria were also compared histologically. In order to evaluate the occurrence of red fillet, subsamples of acceptable and rejected fillets were obtained biweekly from a commercial processing plant over the course of a year, with rejected fillets sorted as red, punctured, or neither. Red fillets accounted for an average of 0.13% fillets from each pond harvest, representing an estimated annual loss of $443,000 for catfish farmers and $683,000 for catfish processors. Red and punctured fillets did not significantly differ in color (lightness and redness), pH, fat, protein, or moisture. Red and punctured fillets were darker, redder, and yellower than acceptable fillets. Acceptable fillets had more fat and less moisture than red and punctured fillets. Microbial analyses were similar for both red and punctured fillets with Aeromonas sobria being the most prevalent bacterium (62%) followed by Plesiomonas shigelloides (28%) and A. hydrophila (19%). Fewer acceptable fillets had bacteria than red or punctured fillets, with A. sobria as the most abundant bacterium (24%). The prevalence of A. sobria in red catfish fillets may warrant further investigation into the effect of bacteria on the development of red fillets in intensively-reared Channel and Hybrid Catfish.