EFFECT OF TRISODIUM PHOSPHATE ON LISTERIA-MONOCYTOGENES ATTACHED TO RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) AND SHRIMP (PENAEUS SPP) DURING REFRIGERATED STORAGE

The potential of using trisodium phosphate (TSP) to reduce bacterial p opulations in fresh fishery products was explored since TSP has recent ly been approved by USDA for its usage in poultry processing to elimin ate Salmonella contamination. Fresh headed shrimp and rainbow trout fi llets were inoculated with L. monocytogenes before dipped in tap water , 10% TSP, or 20% TSP solutions and overwrap-packaged. Surface pH valu es, psychrotrophic plate counts, and L. monocytogenes counts of inocul ated shrimp and trout fillets were determined after 0, 3, 6, and 9 day s of storage at 4C. The TSP treatment resulted in relatively high resi dual surface pH values (11-12) initially in both shrimp and trout fill ets. Compared to tap water dipping, TSP treatment did not significantl y reduce psychrotrophic or Listeria populations in shrimp. However, th e 20% TSP treatment significantly (p<0.05) lowered 0-day psychrotrophi c and L. monocytogenes counts of trout fillets and remained effective for 6 days during storage at 4C.