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Traditional plating methods for bacterial enumeration can be limited, but the development of high-throughput DNA sequencing, such as Oxford Nanopore Technologies (ONT), can provide rapid and highly specific alternative for species-level identification. In this study, ONT amplicon sequencing was applied to fresh broiler breast meat to identify their bacterial composition and monitor their dynamic changes. The sequencing data were complemented by sensory panels, physicochemical analysis, and traditional plating methods. Over time, the bacterial diversity decreased within and across samples. By the end of shelf-life, Pseudomonas fragi, Pseudomonas lundesis, and Brochothrix thermosphacta became the most prevalent species. These bacteria were associated with spoilage attributes that were reported in the sensory panels. This study demonstrated the effectiveness of Nanopore sequencing in determining the spoilage associated bacteria in chicken meat. Future research may focus on developing targeted interventions to mitigate the impact of these spoilage bacteria and extend the shelf life of chicken meat.

Made available in DSpace on 2015-03-26T13:52:03Z (GMT). No. of bitstreams: 1 texto completo.pdf: 406557 bytes, checksum: f8e8d62d3ae14f56df99a0e2bc645da0 (MD5) Previous issue date: 2006-04-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Bacteriocins from lactic acid bacteria have been suggested as an alternative to traditional food preservation methods, such as heat treatment, that interfere with natural characteristics of the food. Nisin is the bacteriocin that has been most used in foods. Recently, a new bacteriocin, bovicin HC5, produced by Streptococcus bovis HC5, was characterized. Previous work indicated that this bacteriocin has activity against Listeria monocytogenes and Clostridium sporogenes. In this study, the activity of this bacteriocin was tested against Bacillus cereus, Bacillus thuringiensis and Clostridium tyrobutyricum isolated form spoiled mango pulp. The addition of bovicin HC5 (40 to 160 AU/mL) into BHI media resulted in reduced specific growth rate and maximal optical densities of B. cereus, B. thuringiensis and C. tyrobutyricum. Concentrations of 40 and 80 AU/mL increased lag phase duration for at least 10 h. When 160 AU/mL was used, growth was not observed even after 144 h. The effect of bovicin HC5 against vegetative cells inoculated into mango pulp was bactericidal and more pronounced at acidic conditions. After 24 h of incubation with the bacteriocin, the viable cell number was bellow the detection level. Similar results were obtained when nisin was used. When C. tyrobutyricum was inoculated into mango pulp with 100 AU/mL of bovicin HC5, gas production was not observed for at least 10 days of incubation. Bovicin HC5 reduced spore germination of B. cereus and B. thuringiensis inoculated into mango pulp, and the number of non-germinated spores after 122 h of incubation was at least 100-fold greater than control treatments. Bovicin HC5 did not affect the thermal resistance of B. cereus and B. thuringiensis spores. However, if added to the mango pulp, bovicin HC5 could remain stable during the heat treatment, and reduce spore germination of these microorganisms. Cultures of B. cereus, B. thuringiensis and C. tyrobutyricum that were transferred successively in the presence of subletal doses of bovicin HC5 did not become resistant. Considering the results obtained in this study and the fact that bovicin HC5 was stable in culture supernatants and in mango pulp, it seems that this bacteriocin could be useful to prevent the spoilage of mango pulp by B. cereus, B. thuringiensis and C. tyrobutyricum. / Bacteriocinas de bactérias do ácido láctico têm sido propostas como alternativa aos métodos tradicionais de conservação de alimentos, como tratamento térmico, que interferem nas características naturais do alimento. A nisina é a bacteriocina que tem sido mais utilizada em alimentos. Recentemente, uma nova bacteriocina, bovicina HC5 produzida por Streptococcus bovis HC5, foi caracterizada e apresentou efetividade contra Listeria monocytogenes e Clostridium sporogenes. Neste estudo, a atividade desta bacteriocina foi testada contra Bacillus cereus, Bacillus thuringiensis e linhagens de Clostridium tyrobutyricum isolados da polpa de manga deteriorada. A adição de 40 a 160 UA/mL de bovicina HC5 em caldo BHI resultou na diminuição da velocidade específica de crescimento e da DO máxima atingida por B. cereus, B. thuringiensis e C. tyrobutyricum. Concentrações de 40 e 80 UA/mL de bovicina HC5 resultaram no aumento da fase lag dos isolados em pelo menos 10 h e quando a concentração utilizada foi de 160 UA/mL, o crescimento não foi observado por, pelo menos, 144 h. Concentração de 100 UA/mL de bovicina HC5 foi bactericida para células vegetativas inoculadas em polpa de manga e este efeito foi mais pronunciado em condições acídicas. Após 24 horas de incubação na presença da bacteriocina, o número de células viáveis das bactérias avaliadas ficou abaixo do limite de detecção. Resultados semelhantes foram obtidos com a nisina. Quando as linhagens de C. tyrobutyricum foram inoculadas em polpa de manga contendo 100 UA/mL de bovicina HC5, a produção de gás não foi observada por até 10 dias de incubação. Bovicina HC5 reduziu a germinação de esporos de B. cereus e B. thuringiensis e o número de esporos no estado dormente após 122 h de incubação foi, pelo menos, 100 vezes maior do que o observado no tratamento controle, sem bacteriocina. Esta bacteriocina não teve efeito na resistência térmica de esporos de B. cereus e B. thuringiensis. Entretanto, uma vez que a bovicina HC5 apresenta resistência a altas temperaturas (121 ºC/20 min), ela pode permanecer estável na polpa de manga após o tratamento térmico e reduzir a germinação dos esporos sobreviventes. A transferência dos isolados por, aproximadamente, 40 gerações na presença de 20 UA/mL de bovicina HC5 não causou adaptação dos microrganismos deterioradores. Esta bacteriocina permaneceu estável após incubação em mistura com o sobrenadante das culturas e com a polpa de manga. Considerando os resultados obtidos neste trabalho, a bovicina HC5 parece ser útil para reduzir a deterioração de polpa de manga causada por B. cereus, B. thuringiensis e C. tyrobutyricum.