Efeito do cloro na etapa pré-insensibilização sobre a qualidade microbiológica de carcaças de rã-touro (Lithobates catesbeianus)

Abstract

In Brazil, the bullfrog (Lithobates catesbeianus) is classified as fish by the Regulation of Industrial and Sanitary Inspection of Products of Animal Origin – RIISPOA, and must be slaughtered and processed under official inspection regime, and following the precepts of humane slaughter and control hygienic-sanitary. It is known that frogs are possible reservoirs of food-borne pathogens, such as Salmonella spp., and it is essential to understand how meat is contaminated and to standardize the slaughter and processing stages through legislation, which still does not exist in the country. That said, the present work aimed to evaluate the effect of different chlorine concentrations on the microbiological contamination of bullfrog carcasses in the pre-slaughter stage. This evaluation was carried out by counting the hygiene indicator microorganisms, namely mesophilic aerobic bacteria (AM), coliforms at 35°C (C35) and E. coli, as well as the occurrence of Salmonella spp. For this purpose, 142 samples of bullfrog carcasses were collected at two slaughter points, post-bleeding (A) and post-cleaning (B). The frogs underwent a previous treatment immersed for 10 minutes in buckets containing water (control group) and different concentrations of chlorine (5, 65 and 125 ppm). The method of collecting these samples was superficial rinsing of the carcass with saline solution, an the techniques used in the counts of hygiene indicator microorganisms were, the pour plate with agar Plate Count Agar (PCA) for AM, Petrifilm TM EC for E coli and C35; and the international identification standards, ISO 6579, for Salmonella spp, with subsequent confirmation by the PCR technique (invA and ompC genes). Through the analyses, the concentrations of 65 and 125 ppm of chlorine were able to reduce the AM count in step B, when compared to the control group, which are statistically equivalent to 5 ppm. For C35, there was no statistical difference between any of the groups, as well as between the slaughter stages. There was low occurrence of E. coli and Salmonella spp in the samples. Finally, the use of 5 ppm of chlorine in the pre-stunning stage is indicated in view of its effectiveness and cost-effectiveness in relation to higher concentrations.