Phosphate type affects the quality of injected catfish fillets

Catfish fillets were injected to 115% over green weight prior to tray-packing and storage at 4 degrees C for 1, 4, 8, and 11 d. Fillets were evaluated for yields, surface color, pH, cooking loss, tenderness, purge loss, and shelf-life. All phosphate treatments increased (P < 0.05) fillet tenderness, but the agglomerated blend of sodium phosphates (AGSP) increased (P < 0.05) pH and yields, and decreased (P < 0.05) CIE L* and CIE b* values. Psychrotrophic plate counts (PPC) of fillets treated with the agglomerated blend of polyphosphates (AGPP) were lower (P < 0.05) than the control at each storage time, but PPC of all samples reached 7 log CFU/g by day 8 of storage. All agglomerated phosphates and STP (sodium tripolyphosphate) improved yields and quality when compared to the nonmarinated control. However, AGSP was the most effective phosphate at increasing pick-up and yields and decreasing cooking loss due to the pH effect that causes more water to be trapped within the food system. Major quality differences may not have occurred between STP and agglomerated phosphates (other than AGSP) since injection relies solely on pH and ionic strength for marinade pickup, whereas tumbling also relies on mechanical action, which relies more on the presence of various phosphate chain lengths and solubility to impact yields. All phosphate treatments improved the quality of tray-packed, refrigerated catfish fillets that were enhanced through multineedle injection. However, AGSP also increased fillet pH, optimized yields, and improved color.

Use of an agglomerated phosphate blend with a high pH (AGSP) maximized the yield of catfish fillets that were marinated through multineedle injection. In addition, STP and agglomerated phosphate blends increased the yield and tenderness of catfish fillets when compared to the nonmarinated control.