Effects of different concentrations of sodium azide and chloramphenicol on the preservation of raw milk samples / Efeitos de diferentes concentrações de azida sódica e cloranfenicol na preservação de amostras de leite cru

The preservation of milk samples for microbiological analyses by the Brazilian Network of Milk Quality Control Laboratories requires the addition of preservatives to maintain the microbiota from the time of sample collection to the moment of analysis. The number of microorganisms can change as a result of the active ingredients and concentration of the preservative, as well as due to interactions between the preservatives, incubation time, and packaging temperature. The objective of this research was to evaluate the conservation potential of different concentrations of sodium azide and chloramphenicol on the analytical shelf life of milk samples. Two farms were selected, one with a low bacterial count and one with a high bacterial count. The milk was dispensed into sterile vials and tested after the addition of the usual concentrations of sodium azide and chloramphenicol, doubled concentrations, tripled concentrations, and as a control, without preservatives. The samples were incubated at 3 ± 1 °C, 6 ± 1 °C, and 9 ± 1 °C for 14 days and analyzed daily for their bacterial count by flow cytometry. The tripled preservative concentrations improved conservation, increasing the timespan of the analytical viability of the samples without altering the results.(AU)

A conservação das amostras de leite destinadas para análises microbiológicas pela Rede Brasileira de Laboratórios de Controle da Qualidade do Leite requer adição de conservantes para a preservação da microbiota existente desde o momento da coleta até as análises. O número de microrganismos pode apresentar alterações decorrentes do princípio ativo e concentração do conservante, e ainda entre as interações conservante, tempo de incubação e temperatura de acondicionamento. O objetivo deste trabalho foi avaliar o potencial de conservação de diferentes concentrações de azida sódica e cloranfenicol sobre a vida útil analítica de amostras de leite. Foram selecionadas duas fazendas, sendo uma com baixa contagem bacteriana e outra com alta contagem bacteriana. O leite foi fracionado em frascos estéreis e testado nas seguintes condições: pastilhas com a concentração usual de azida sódica e cloranfenicol, com dupla concentração, com tripla concentração e sem a adição do conservante. As amostras foram incubadas por quatorze dias a 3 ± 1 °C, 6 ± 1 °C e 9 ± 1 °C, e analisadas diariamente por citometria de fluxo para a determinação da contagem bacteriana. A tripla concentração do conservante demonstrou maior conservação, possibilitando o aumento da viabilidade analítica das amostras sem alteração nos resultados.(AU)

Quantificação de Staphylococcus aureus e bactérias mesófilas aeróbias para avaliar higienização de equipamentos de ordenha / Staphylococcus aureus and mesophilic aerobic bacteria quantification in hygienization process of milking equipment

Background: Milk’s composition is an excellent substrate for microorganism’s multiplication. Presence of Staphylococcusaureus and aerobic mesophilic bacteria are one of the most common problems in dairy farms. On dairy industry’s and milkfarms Clean in Place (CIP) system higyenization are commonly used, then the cleaning occurs as a closed process, forbetter results sanitizans are applied, in order to obtain a safety food. This project aim to evaluate Staphylococcus aureusand aerobic mesophilic bacteria reduction after two milking higyenization process.Materials, Methods & Results: This research was done on a Rio Grande do Sul North Milk farm, with mechanized milkingand Clean in Place system for cleaning. For liners and CIP tubes higyenization commercial products as Sodium Hipoclorite3% and phosphoric acid 11.3% are used for detergency, and peracetic acid 5% for sanitization. Milk bunk tank are higyenized with sodium hypoclorite 3.8% alcalin detergent. After higyenization steps liners, CIP’s water process, bulk milk tankand milk set were collected. At process 1, liners and CIP water were collected after milking, detergency and sanitizationthat occurred immediately at the detergency’s finish, while process 2 the sanitization was realized 8 h after detergency,before following milking. Cooling milk bulk tank was collected before and after detergency, and milk set after milkingsConvencional microbiology were used to count and results in log10 UFC.cm-2...

Quantificação de Staphylococcus aureus e bactérias mesófilas aeróbias para avaliar higienização de equipamentos de ordenha / Staphylococcus aureus and mesophilic aerobic bacteria quantification in hygienization process of milking equipment

Background: Milks composition is an excellent substrate for microorganisms multiplication. Presence of Staphylococcusaureus and aerobic mesophilic bacteria are one of the most common problems in dairy farms. On dairy industrys and milkfarms Clean in Place (CIP) system higyenization are commonly used, then the cleaning occurs as a closed process, forbetter results sanitizans are applied, in order to obtain a safety food. This project aim to evaluate Staphylococcus aureusand aerobic mesophilic bacteria reduction after two milking higyenization process.Materials, Methods & Results: This research was done on a Rio Grande do Sul North Milk farm, with mechanized milkingand Clean in Place system for cleaning. For liners and CIP tubes higyenization commercial products as Sodium Hipoclorite3% and phosphoric acid 11.3% are used for detergency, and peracetic acid 5% for sanitization. Milk bunk tank are higyenized with sodium hypoclorite 3.8% alcalin detergent. After higyenization steps liners, CIPs water process, bulk milk tankand milk set were collected. At process 1, liners and CIP water were collected after milking, detergency and sanitizationthat occurred immediately at the detergencys finish, while process 2 the sanitization was realized 8 h after detergency,before following milking. Cooling milk bulk tank was collected before and after detergency, and milk set after milkingsConvencional microbiology were used to count and results in log10 UFC.cm-2...(AU)