An extraordinary dairy phage and its properties: Occurrence, growth, inactivation, survival

Abstract

Lactococcus lactis phages can be very heat resistant and phage P680 survive pasteurisation. In this work, phage growth, thermal and non-thermal as well as chemical methods were presented together and re-evaluated in the elimination of P680. A fermentation failure within 2 h can occur under the presence of phage P680, which survived heating at 95 °C for 5 min. Up to 4 log units of reduction could be achieved using membrane filtration (cut-off 100 nm). In case of ultraviolet-C treatment, doses up to 0.05 J cm−2 and 4 J cm−2 were required for phage P680 to achieve 6 log units reduction in water and 8 log units reduction in filtered whey. Phage P680 was mostly resistant at pH levels of 3 and 10 (<0.5 log reduction), however, a significant drop of the phage levels was observed at pH values of 2 and 12 (∼6 log units of reduction).