Improved methods for the enumeration of heterotrophic bacteria in bottled mineral waters |
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Authors: | Ramalho R Cunha J Teixeira P Gibbs P A |
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Institution: | Escola Superior de Biotecnologia, R. Dr. António Bernardino de Almeida, 4200-072, Porto, Portugal. |
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Abstract: | At this time the European Union regulations require that the heterotrophic plate counts (HPC) of mineral waters be assessed at two recovery temperatures: 22 degrees C for 72 h and 37 degrees C for 24 h. This procedure is time consuming and expensive. Development of new rapid methods for microbiological assessment of the microbial flora in the bottled water is an industry-driven need.The objectives of this work were to develop a method for the HPC that utilises only one recovery temperature and one incubation period and evaluate the use of, the LIVE/DEAD(R) BacLight Bacterial Viability Kit, 5-cyano-2,3-ditotyl tetrazolium chloride (CTC) and impedance methods to enumerate viable bacteria in bottled mineral water.Results showed that incubation at 30 degrees C could be used instead of incubation at 22 degrees C and 37 degrees C. Good correlation exists between counts at 30 degrees C and counts at 22 degrees C (r>0.90) and all the pathogens important in mineral water analyses grow similarly at 30 degrees C and 37 degrees C during 24 h.It was demonstrated that impedance methods might be useful to the mineral water industry as a rapid indicator of microbiological quality of the water.Results obtained with BacLight and CTC were similar to those obtained with plate counts. |
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