Improved methods for the enumeration of heterotrophic bacteria in bottled miner...

• Author(s): Ramalho, Rita ; Cunha, Joaquim ; Teixeira, Paula ; Gibbs, Paul A.
• Date: 2001
• Persistent ID: http://hdl.handle.net/10400.14/6841
• Origin: Veritati - Repositório Institucional da Universidade Católica Portuguesa
• Subject(s): BacLight; CTC; Heterotrophic plate counts; Impedance methods; Mineral water
• Document Type: Article
• Language: English

Description

At this time the European Union regulations require that the heterotrophic plate counts (HPC) of mineral waters be assessed at two recovery temperatures: 22°C for 72 h and 37°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® 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°C could be used instead of incubation at 22°C and 37°C. Good correlation exists between counts at 30°C and counts at 22°C (r>0.90) and all the pathogens important in mineral water analyses grow similarly at 30°C and 37°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.