Note. Reaction of Bacteria Associated with Fish Spoilage to Chemical and Physical Stress

Abstract

A cocktail made up of six bacteria isolated from fish was subjected to various heats (30°C and 60°C, 20 s) and chemical preservative stresses, alone and in combination. The chemical preservatives tested were potassium sorbate (PS, 1%), trisodium phosphate (TSP, 10%) and tetrasodium pyrophosphate (TSPP, 3%). Heating the bacteria at 60°C for 20 s resulted in an average reduction of 2.0 log cfu/mL in the total number. The results showed a marked synergistic effect of heat treatment prior to chemical additives, especially for TSPP and sorbate; no significant effect was evident when chemicals were applied alone. The effect was increased by the application of chemical preservatives, before heating, in the decreasing order TSP, TSPP and sorbate; reductions obtained were more than 5.0, 4.0 and 3.0 log cfu/mL, respectively. The synergistic effect observed was dependent on the type of chemical additives used and also on the order of the treatments. Bacteria identified as Shewanella putrefaciens and Pseudomonas putida were more resistant to heat treatment and Brochothrix thermosphacta and Lactobacillus plantarum were more resistant to TSP treatment. These bacteria in the cocktail showed high sensitivity to combined TSP/heat treatment; bacterial cells identified as Enterobacter spp. were the most resistant to this treatment.Se preparó una mezcla con seis bacterias aisladas de peces y se sometieron a distintos tratamientos térmicos (30°C y 60°C, 20 s) y de conservantes químicos, por separado y en combinación. Los conservantes químicos empleados fueron sorbato de potassio (PS, 1%), fosfato trisodico (TSP, 10%) y pirofosfato tetrasodico (TSPP, 3%). El calentamiento a 60°C durante 20 s redujo una media de 2.0 log cfu/mL del recuento total de bacterias. Se observó un efecto sinérgico marcado cuando el calor precedía a los tratamientos químicos, de modo más evidente para el TSPP y para el sorbato de potassio; sin embargo no fue significativo el efecto cuando los tratamientos químicos se aplicaron solos. El efecto aumentó cuando los conservantes químicos se aplicaron antes del calor, según el orden decreciente TSP, TSPP y sorbato; las reducciones obtenidas fueron de más de 5.0, 4.0 y 3.0 log cfu/mL, respectivamente. El efecto sinérgico dependió del tipo de aditivo químico y también de la secuencia de los tratamientos. Las bacterias identificadas como Shewanella putrefaciens y Pseudomonas putida fueron las más resistentes al calor; Brochothrix thermosphacta y Lactobacillus plantarum mostraron más resistencia al tratamiento con TSP. Estas bacterias de la mezcla revelaron una alta sensibilidad al tratamiento combinado TSP/calor; las células bacterianas identificadas como Enterobacter spp. fueron las más resistentes a este tratamiento.

Control of Histamine‐Producing Bacteria and Histamine Formation in Fish Muscle by Trisodium Phosphate

“…Several researchers have investigated the effect of phosphates on various bacteria from fish. Kirby and others () found that 10% solution of TSP resulted in a 1.5 log CFU/mL decrease in a cocktail of 6 bacteria isolated from fish including, Photobacterium phosphoreum and Enterobacter spp. Some of these bacteria have been reported to produce high levels of histamine (Takahashi and others ).…”