Hipoclorito de sódio (NaClO) para inativação de Salmonella spp. no contexto do processamento de peixes : concentração x tempo de exposição

Abstract

Aquaculture is one of the fastest growing food production sectors in recent years (FAO, 2018). All indicators of quality, productivity potential and demand expectations point to fish as the animal protein of the future. Salmonella ssp. has been identified as the main cause of food-borne bacterial diseases in man, which is infected by eating contaminated food.Fish is not a natural reservoir of Salmonella spp. even so, this pathogen has been identified and considered a challenge to guarantee the safety of the fish during its processing. Chlorinated products are sanitizers widely used to eliminate pathogenic microorganisms in the food industry. In addition, in Brazil, chlorine is currently the only disinfectant allowed for the fish washing process. In this context, the present study aimed to determine the Minimum Inhibitory Concentration (MIC) of sodium hypochlorite (NaClO), and to evaluate the survival of Salmonella Typhimurium and Salmonella Ndolo in chlorinated water with and without presence of the fish organic material to calculate D. value. MIC was performed by the macrodilution method in tubes, and two serovars were challenged with chlorinated water at 5 ppm and 50 ppm, and bacteria survavial was evaluated in up to five different times (5, 30, 60, 90 and 120 minutes). The Results revealed a MIC of free chlorine NaClO for Salmonella Typhimurium and S. Ndolo of 0.76 ± 0.24 ppm and 0.28 ± 0.03 ppm, respectively. In vitro, a free chlorine of 5 ppm, shows a reduction of 2.6 and 3.8 logs CFU / mL of Salmonella Typhimurium and S. Ndolo, respectively, as well a D5ppm of 25 and 16 minutes to each one. The presence of 10% organic matter demonstrated a direct relationship with decrease ot the antimicrobial effect of NaClO, affecteded by chemicals factors (pH, total chlorine and free chlorine), increasing the survival of S. Typhimurium and multiplied by 4 times the D5ppm value. However, under organic matter conditions, S. Typhimurium is completely inactivated when submitted to water with 50 ppm of free chlorine NaClO, even with fish organic matter. Thus, we concluded that Salmonella spp. from fish is sensible at low free chlorine concentrations, but in vitro results reveal that water in neutral pH with 5 ppm of free chlorine NaClO is ineffective to inactivate 4 Logs of Salmonella Ndolo and S. Thyphimurium, while 50 ppm allows to inactivate quickly the same population, so this concentration of free chlorine has potential to control Salmonella spp. in fish processing.