Influence of time and storage temperature on raw milk deteriorating microbiota / Influência do tempo e temperatura de estocagem sobre a microbiota deteriorante do leite cru

The quality of raw milk depends on initial microbial contamination and conditions of storage until industry processing. Considering the influence of time and storage temperature on raw milk microbiota, the objective of this work was to quantify and monitor the multiplication of these groups under different conditions. For this purpose, 41 samples of raw milk were collected immediately after milking, stored in the following storage conditions: 25 °C/2 h; 35 °C/2 h; 7 °C/24 h; 7 °C/48 h and 7 °C/60 h and analyses of aerobic mesophilic, psychrotrophic and proteolytic psychrotrophic microorganisms. The milk samples analyzed in the study had an initial mean count of mesophilic aerobes of 5.38 Log CFU/mL at Time Zero. The milk stored at 25 °C/2 h and 35 °C/2 h kept the mesophilic aerobic counts within the limits established by the legislation (5.48 Log CFU/mL), with an increase in counts of psychrotrophic and proteolytic microorganisms. When stored at 7 °C/24 h and 7 °C/48 h, the count of mesophiles exceeded the established parameters. A significant increase in the count of proteolytic psychrotrophs and psychrotrophs was also observed during storage at 7 °C from 24 h. The results of this study indicate that the temperature of 7 °C is not suitable for the milk conservation, since it was not able to control the microbial multiplication. Thus, the results contribute to the change in milk storage temperature proposed by the new Brazilian legislation.(AU)

A qualidade do leite cru depende da contaminação microbiana inicial e das condições de armazenamento até o processamento na indústria. Considerando a influência do tempo e da temperatura de armazenamento na microbiota do leite cru, o objetivo deste trabalho foi quantificar e monitorar a multiplicação desses grupos de microrganismos sob diferentes condições. Para tanto, foram coletadas 41 amostras de leite cru imediatamente após a ordenha, armazenadas nas seguintes condições de armazenamento: 25 °C/2 h; 35 °C/2 h; 7 °C/24 h; 7 °C/48 h e 7 °C/60 h para análise de microrganismos psicrotróficos, aeróbios mesófilos, psicrotróficos e proteolíticos. As amostras de leite analisadas no estudo apresentaram uma contagem média inicial de aeróbios mesófilos de 5.38 Log UFC/mL no Tempo Zero. O leite armazenado a 25 °C/2 h e 35 °C/2 h manteve as contagens aeróbias mesófilas dentro dos limites estabelecidos pela legislação (5,48 Log UFC/mL), com aumento nas contagens de microrganismos psicrotróficos e proteolíticos. Quando armazenado a 7 °C/24 h e 7 °C/48 h a contagem de mesófilos excedeu os parâmetros estabelecidos. Um aumento significativo na contagem de psicrotróficos e psicrotróficos proteolíticos também foi observado durante o armazenamento a 7 °C a partir das 24 h. Os resultados deste estudo indicam que a temperatura de 7 °C não é adequada para a conservação do leite, uma vez que não foi capaz de controlar a multiplicação microbiana. Assim, os resultados contribuem para a mudança na temperatura de armazenamento de leite proposta pela nova legislação brasileira.(AU)

A Real-Time Reverse-Transcription Polymerase Chain Reaction for Differentiation of Massachusetts Vaccine and Brazilian Field Genotypes of Avian Infectious Bronchitis Virus.

The avian infectious bronchitis virus is classified into serotypes or genotypes (or both) in different poultry-producing countries of the world. In Brazil, Massachusetts type (Mass), used as a live vaccine, and local field Brazilian variants (genotypes; BR) predominate in the commercial poultry flocks. This study describes the development and validation of two real-time reverse-transcription polymerase chain reactions (RT-qPCR) for the specific detection of Mass and BR genotypes in allantoic fluids and clinical samples. Genotype-specific primers, combined with a generic probe targeted to the S1 gene, originated Mass RT-qPCR and BR RT-qPCR-specific assays. Analytical sensitivity and linearity of these assays were determined in comparison with an IBV generic real-time RT-PCR based on the 5' untranslated region (5'UTR RT-qPCR). Mass RT-qPCR detected five Mass field isolates, three vaccine samples, and one coinfected sample (BR and Mass) while BR RT-qPCR detected 16 BR field isolates. Both assays were linear (R(2) > 0.98), reproducible, and as sensitive as the classical 5'UTR RT-qPCR used to detect IBV. In the analysis of 141 IBV clinical samples, 8 were positive for Mass RT-qPCR, 76 for BR RT-qPCR, and 2 for both assays. In the remaining 55 samples, 25 were positive only for 5'UTR RT-qPCR and 30 were negative for the three assays. In conclusion, both assays were able to detect Mass and BR genotypes, allowing rapid and easy IBV molecular typing from allantoic fluids and clinical samples.