Extreme thermal resistance of phages isolated from dairy samples: updating traditional phage detection methodologies

CAPRA, M. L.; NEVE, H.; SORATI, P.; ATAMER, Z.; HINRICHS, J.; HELLER, K.; QUIBERONI, A.

INTERNATIONAL DAIRY JOURNAL

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2013 vol. 30 p. 59 - 63

0958-6946

Starter culture failures due to bacteriophage attacks reduce product quality and cause considerable financial losses. Phage monitoring is critically important for dairy industry for identifying contamination sources in the plant and for assessing contamination levels, allowing rapid decision-makings in case of severe phage infections. Standard microbiological methods are still crucial to detect phages because they allow the identification of active phage particles. Besides their recognized hardness against pasteurization, several phages isolated in the last years from dairy environments exhibited extraordinary 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 to contain phages. A prolonged heating-step of 45 min at 90ºC is proposed.