Growth potential of Yersinia enterocolitica in pasteurised cow's and goat's milk stored at 8 °C and 24 °C
| Authors | |
|---|---|
| Year of publication | 2017 |
| Type | Article in Periodical |
| Magazine / Source | Food Control |
| MU Faculty or unit | |
| Citation | |
| Doi | http://dx.doi.org/10.1016/j.foodcont.2016.11.006 |
| Field | Other medical specializations |
| Keywords | Baranyi-Roberts model; Risk assessment; Foodborne pathogen |
| Description | Milk and dairy products are among the most commonly consumed foods. The shelf life of pasteurised milk and many other dairy products is guaranteed, among others, when stored at 4–8 °C. These temperatures, however, will not prevent the growth of psychrotrophic bacteria, including some foodborne pathogens such as Yersinia enterocolitica. The study examines the growth potential of Y. enterocolitica in pasteurised cow's and goat's milk at different storage conditions (at a refrigerated temperature of 8 °C and an improper storage temperature of 24 °C). Y. enterocolitica growth dynamics was studied using a mathematical model for microbial growth. The behaviour of Y. enterocolitica depends on storage temperature and inoculum size and does not differ between cow's and goat's milk. The growth curve of Y. enterocolitica cultivated at 8 °C included the lag, exponential, and stationary phases. Both, the duration of the lag phase and growth rate did not differ between milk samples inoculated with the low (approximately 1 log cfu ml-1) or high (3 log cfu ml-1) inoculum size. The stationary phase was reached (with the peak number of the bacteria produced) within eight and six days with the low and high inoculum size, respectively. The growth of the bacteria at 24 °C was exponential from the first hour, peaking within two to three days or slightly later with the low inoculum size. The maximum cell concentration did not depend on inoculum size and cultivation temperature, reaching 9 log cfu ml-1 in all cases. Due to its composition and absence of competitive microflora, pasteurised milk provides a favourable environment for the growth of Y. enterocolitica. In case of contamination of pasteurised milk, even with a low amount of Y. enterocolitica, the bacterium multiplies to an infective dose within hours or days, depending on the storage temperature. |