Catfish fillets were minced and acid (pH 3.0) solubilized in dilute conditions (1:9). Insolubles were removed by centrifugal force (3000 xg) and the soluble protein was recovered by isoelectric precipitation (pI approximately 5.4). Moisture and NaCl of the batters were equilibrated to 78% and 2%, respectively. Samples were stuffed into casings, cooked, and chilled. Proximate composition, color, cook yield, water holding ability (WHA), and texture profile analysis (TPA) were determined. Treatment of catfish protein by the solubilization process removed 74% of the fat. In addition, gels from treated protein were less red (-1.61 compared with -1.06) and yellow (6.58 compared with 7.09). There was no difference in whiteness (72.0 compared with 71.8) of gels or in percent cook yield (94.6% compared with 95.0%) between treated protein and the control, respectively. The WHA of gels made from control protein was 0.73 g/g protein higher than treated. The texture analysis indicated that treated proteins had significantly higher hardness (1193 g compared with 1046 g), springiness (0.919 compared with 0.897), chewiness (0.701 compared with 0.584), and cohesiveness (0.637 mJ compared with 0.619 mJ). The resilience was equivalent for both treated and control gels. The results indicated the protein solubilization process produced a low fat protein product with good gel strength properties.

Single-and mixed-size cohorts of small (18 g) and intermediate (34 g and 60 g) fingerlings, and stocker (270-300 g) channel catfish, Ictalurus punctatus, were grown in ponds at 12,500/ha for two years.Year 1 compared single cohorts (18 g, 60 g, or stockers) to mixedsize culture of these cohorts. Year 2 compared a mixed-cohort treatment (18 g, 34 g, and carryover (CO) fish), and two, two-cohort treatments (18 g or 34 g and CO). Daily growth of 18-g fingerlings was less in triple-than single-cohort culture (0.98 g/day vs. 1.55 g/day) during Year 1. Sixty-gram fingerlings and stocker-size fish grew less (P < 0.05) alone than in triple cohorts. Stockers also grew more (P < 0.05) in double-than single-cohort culture. Nearly 29% of single cohort 18-g fingerlings reached marketable size (Ն 600 g); 14% in double cohorts, and none in triple cohort ponds. All pairwise comparisons of diet costs were significantly different during Year 1. All pairwise comparisons of yield from Year 1 were significantly different. Yield was similar among treatments during Year 2, and for the study totals. Return over fingerling and diet costs during Year 1 was greatest from single-cohort culture of stockersize fish ($5885/ha). Return was similar among treatments during Year 2 ($6803-$7197/ha). All pairwise comparisons for the project totals were significantly (P < 0.05) different. Multicohort culture pro-Please note that this electronic prepublication galley may contain typographical errors and may be missing artwork, such as charts, photographs, etc. Pagination in this version will differ from the published version.

Use of a sieve as an economic alternative for the pH-shift process was evaluated for removing off-flavors from catfish. Difficulties were encountered with regard to protein recovery using the sieve and suggestions are made to, perhaps, make the process more applicable for a sieve-based recovery step. The process as described reduced off-flavors, but only 2-fold suggesting the process would work best on catfish near or just over off-flavor thresholds. Results also indicated the pH-shift process could be used to improve texture of a fried catfish product designed to be similar to chicken nuggets.

Conditions that optimize 2-methylisoborneol (MIB) and geosmin reduction by protein solubilization were evaluated in channel catfish. For both MIB and geosmin spiked fish, acid and alkaline solubilizations effectively (p < 0.001) reduced off-flavor. Average MIB and geosmin levels for untreated, unprocessed fish were 1.396 and 1.992 ppb, respectively. Pooled centrifuge levels for treated fish were: 0.194 ppb MIB and 0.398 ppb geosmin using citric acid; 0.104 ppb MIB and 0.258 ppb geosmin using phosphoric acid; 0.143 ppb MIB and 0.543 ppb geosmin using acetic acid; and 0.0987 ppb MIB and 0.426 ppb geosmin using alkaline (sodium hydroxide) conditions. Centrifugation did not significantly affect (p = 0.999) off-flavor removal for MIB, however it did significantly affect (p = 0.05) geosmin removal.