RESULTS

1. Gelation of Protein Recovered From Rainbow Trout (Oncorhynchus mykiss) Processing By-product RESULTS MATERIALS AND METHODS Summary INTRODUCTION OBJECTIVES ABSTRACT Y.C. Chen and J. Jaczynski West Virginia University, Animal & Veterinary Sciences Acid- and alkali-treated proteins showed a rapid increase of storage moduli at 50-90ºC. That is, the mixture improved texture of trout gels as confirmed by texture profile analysis and torsion shear stress. Higher torsion shear stress was measured in basic treatments than those in acid treatments. Lower (P<0.05) ash contents of trout paste were obtained using a continuous centrifuge than those from trout fillets. However, the higher (P<0.05) lipid contents were determined in the acid treatments compared with those in the basic treatments. In the color measurement, trout protein gels from acid treatments showed whiter (L*-3b*) (P<0.05) gels than those from basic treatments. Value-added human foods can be developed based on proteins recovered from fish processing by-products using isoelectric solubilization/precipitation in a continuous mode. Filleting fish requires removal of bones, skin, head, and viscera (hereinafter called by-products). Most processors fillet fish by mechanical means. Mechanical filleting of 100 lbs of trout yields 40 lbs of fillets and 60 lbs by-products. The by-products contain 20 lbs of meat. The by-products are reduced to compost, animal feed, or are land-filled. In descriptive terms, per two truckloads of trout fillets going to the market, one truckload of trout meat and a quarter of a truckload of trout lipids un-recovered from by-products are reduced to compost or animal feed. The growth of the aquaculture industry necessitates development of technologies that recover proteins and lipids from filleting by-products and increase the total return. The surimi technology could be a good alternative for recovery of functional proteins, however, the traditional surimi processing cannot recover proteins from the by-products and uses excessively large volumes of water. An isoelectric solubilization/precipitation of fish muscle proteins has recently been applied to isolate functional proteins. This technique offers several advantages including high yield, possible separation of impurities (bones, skin and scales) and a feasible continuous mode of operation, enabling water re-usage. The isoelectric solubilization/precipitation for protein separation was well-studied in the laboratory-scale, but not widely applied in the industry. The aim of this research was to explore an industrial scale procedure. This procedure may bring significant benefits to both, the fish industry and environmental protection. Fig 1. Dynamic properties of trout surimi sol to gel transition as affected by different pH treatments Fig 2. Torsion shear stress of trout protein gels Table3. Color properties of recovered trout protein gels as affected by different pH treatments Table1. Moisture, lipid, protein, and ash contents in recovered trout paste Table2. Texture profiles of trout protein gels as affected by different pH treatments Our objectives were to: 1) test a continuous mode for protein recovery from trout by-products 2) investigate the effects of a mixture containing bovine plasma protein (BPP), potato starch (PS), transglutarminase (Activa), and polyphosphate (PP) on gelation of muscle protein recovered from trout by-product, and 3) compare the textural properties of recovered trout muscle proteins at different acidic and basic pH values. • Test parameters: moisture, lipid, and ash contents of recovered trout protein paste and dynamic property (G’), textural properties, color measurement of trout protein gels. • torsion shear stress comparedwith acid treatments. • Trout protein from basic treatments was more yellow compared to acid treatments, which resulted in whiter gels in acid treatments. • pH 12.0 may be better to recover proteins from trout by-products. • Lipid removal from trout paste will be the next step to obtain better quality of trout surimi. • Recovered trout protein with a mixture showed a rapid increased of storage moduli (G’) from 50-90C. • Lower ash of trout proteins was obtained using continuous centrifuge compared to trout fillets; while higher lipid contents of trout paste were determined in acid treatments. • Trout protein gels recovered from pH 3.0 and 12.0 had higher values in the texture profiles except hardness; meanwhile, basic treatments showed a higher