CONICET | Buscador de Institutos y Recursos Humanos

Starter culture failures due to bacteriophage attacks reduce product quality and may cause financial losses. Phage monitoring is important to the dairy industry for identifying contamination sources in the plant and for assessing contamination levels. Hence, countermeasures can be initiated rapidly in case of severe phage infections. Standard microbiological methods are still crucial to detect phages as they allow the identification of active phage particles. In addition to their recognized resistance against pasteurization, several dairy phages isolated in the last years exhibited extraordinary high thermal resistances. It was the aim of this work to revise and update the Standard IDF microbiological methodology for phage detection which includes a mandatory control, treated for 15 min at 90°C for discrimination of phage- and non-phage inhibitors. Phages specific for Lactococcus lactis, Streptococcus thermophilus, Lactobacillus casei and Lb. paracasei were investigated to establish a reliable heat-treatment for the processing of industrial dairy samples suspected of containing phages. A prolonged heating-step of 45 min at 90ºC is proposed.